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this is the first of three papers that present a detailed guide for working with the codes {\sc tlusty} and {\sc synspec} to generate model stellar atmospheres or accretion disks, and to produce detailed synthetic spectra. in this paper, we present a very brief manual intended for casual users who intend to use these codes for simple, well defined tasks. this paper does not present any background theory, or a description of the adopted numerical approaches, but instead uses simple examples to explain how to employ these codes. in particular, it shows how to produce a simple model atmosphere from the scratch, or how to improve an existing model by considering more extended model atoms. this paper also presents a brief guide to the spectrum synthesis program {\sc synspec}. | a brief introductory guide to tlusty and synspec |
we compute upper limits on the nanohertz-frequency isotropic stochastic gravitational wave background (gwb) using the 9 year data set from the north american nanohertz observatory for gravitational waves (nanograv) collaboration. well-tested bayesian techniques are used to set upper limits on the dimensionless strain amplitude (at a frequency of 1 yr-1) for a gwb from supermassive black hole binaries of {a}{{gw}}\lt 1.5× {10}-15. we also parameterize the gwb spectrum with a broken power-law model by placing priors on the strain amplitude derived from simulations of sesana and mcwilliams et al. using bayesian model selection we find that the data favor a broken power law to a pure power law with odds ratios of 2.2 and 22 to one for the sesana and mcwilliams prior models, respectively. using the broken power-law analysis we construct posterior distributions on environmental factors that drive the binary to the gw-driven regime including the stellar mass density for stellar-scattering, mass accretion rate for circumbinary disk interaction, and orbital eccentricity for eccentric binaries, marking the first time that the shape of the gwb spectrum has been used to make astrophysical inferences. returning to a power-law model, we place stringent limits on the energy density of relic gws, {{{ω }}}{gw}(f){h}2\lt 4.2\quad × \quad {10}-10. our limit on the cosmic string gwb, {{{ω }}}{gw}(f){h}2\lt 2.2\quad × \quad {10}-10, translates to a conservative limit on the cosmic string tension with gμ \lt 3.3× {10}-8, a factor of four better than the joint planck and high-l cosmic microwave background data from other experiments. | the nanograv nine-year data set: limits on the isotropic stochastic gravitational wave background |
the central nuclei of galaxies, where supermassive black holes (smbhs) are thought to reside, can experience phases of activity when they become active galactic nuclei (agns). an agn can eject winds and jets and produce radiation across the entire electromagnetic spectrum. the fraction of the bolometric emission in the radio spans a factor of approximately 105 across the different classes of agns. the weakest radio sources, radio-quiet (rq) agns, are typically 1,000 times fainter than the radio-loud (rl) agns, and represent the majority of the agn population. in rq agns, the absence of luminous jets allows us to probe radio emission from a wide range of possible mechanisms: star formation, agn-driven wind, free-free emission from photoionized gas, low-power jets and the innermost accretion disk coronal activity. all these mechanisms can now be probed with unprecedented precision and spatial resolution, owing to the current and forthcoming generation of highly sensitive radio arrays. | the origin of radio emission from radio-quiet active galactic nuclei |
in recent years, the discovery of massive quasars at has provided a striking challenge to our understanding of the origin and growth of supermassive black holes in the early universe. mounting observational and theoretical evidence indicates the viability of massive seeds, formed by the collapse of supermassive stars, as a progenitor model for such early, massive accreting black holes. although considerable progress has been made in our theoretical understanding, many questions remain regarding how (and how often) such objects may form, how they live and die, and how next generation observatories may yield new insight into the origin of these primordial titans. this review focusses on our present understanding of this remarkable formation scenario, based on the discussions held at the monash prato centre from november 20 to 24, 2017, during the workshop `titans of the early universe: the origin of the first supermassive black holes'. | titans of the early universe: the prato statement on the origin of the first supermassive black holes |
ever deeper and wider look-back surveys have led to a fairly robust outline of the cosmic star-formation history, which culminated around [formula: see text]; this period is often nicknamed "cosmic noon." our knowledge about star-forming galaxies at these epochs has dramatically advanced from increasingly complete population censuses and detailed views of individual galaxies. we highlight some of the key observational insights that influenced our current understanding of galaxy evolution in the equilibrium growth picture: scaling relations between galaxy properties are fairly well established among massive galaxies at least out to [formula: see text], pointing to regulating mechanisms already acting on galaxy growth. resolved views reveal that gravitational instabilities and efficient secular processes within the gas- and baryon-rich galaxies at [formula: see text] play an important role in the early buildup of galactic structure. ever more sensitive observations of kinematics at [formula: see text] are probing the baryon and dark matter budget on galactic scales and the links between star-forming galaxies and their likely descendants. toward higher masses, massive bulges, dense cores, and powerful agns and agn-driven outflows are more prevalent and likely play a role in quenching star formation. we outline emerging questions and exciting prospects for the next decade with upcoming instrumentation, including the james webb space telescope and the next generation of extremely large telescopes. | star-forming galaxies at cosmic noon |
we use the second data releases of the european space agencygaia astrometric survey and the high-resolution galactic archaeology with hermes (galah) spectroscopic survey to analyse the structure of our galaxy's disc components. with galah, we separate the α-rich and α-poor discs (with respect to fe), which are superposed in both position and velocity space, and examine their distributions in action space. we study the distribution of stars in the zv z phase plane, for both vϕ and vr, and recover the remarkable `phase spiral' discovered by gaia. we identify the anticipated quadrupole signature in zv z of a tilted velocity ellipsoid for stars above and below the galactic plane. by connecting our work with earlier studies, we show that the phase spiral is likely to extend well beyond the narrow solar neighbourhood cylinder in which it was found. the phase spiral is a signature of corrugated waves that propagate through the disc, and the associated non-equilibrium phase mixing. the radially asymmetric distribution of stars involved in the phase spiral reveals that the corrugation, which is mostly confined to the α-poor disc, grows in z-amplitude with increasing radius. we present new simulations of tidal disturbance of the galactic disc by the sagittarius (sgr) dwarf. the effect on the zv z phase plane lasts {≳ } 2 gyr, but a subsequent disc crossing wipes out the coherent structure. we find that the phase spiral was excited {≲ } 0.5 gyr ago by an object like sgr with total mass ∼3 × 1010 m⊙ (stripped down from ∼5 × 1010 m⊙ when it first entered the halo) passing through the plane. | the galah survey and gaia dr2: dissecting the stellar disc's phase space by age, action, chemistry, and location |
recently, an anomalous excess was found in the electronic recoil data collected at the xenon1t experiment. the excess may be explained by an axionlike particle (alp) with a mass of a few kev and a coupling to electron of ga e∼10-13, if the alp constitutes all or some fraction of local dark matter (dm). in order to satisfy the x-ray constraint, the alp coupling to photons must be significantly suppressed compared to that to electrons. this strongly suggests that the alp has no anomalous couplings to photons; i.e., there is no u (1 )pq-u (1 )em-u (1 )em anomaly. we show that such anomaly-free alp dm predicts an x-ray line signal with a definite strength through the operator arising from threshold corrections, and compare it with the projected sensitivity of the athena x-ray observatory. the abundance of alp dm can be explained by the misalignment mechanism, or by thermal production if it constitutes a part of dm. in particular, we find that the anomalous excess reported by the xenon1t experiment as well as the stellar cooling anomalies from white dwarfs and red giants can be explained simultaneously better when the alp constitutes about 10% of dm. as concrete models, we revisit the leptophilic anomaly-free alp dm considered in k. nakayama, f. takahashi, and t. t. yanagida [phys. lett. b 734, 178 (2014)] as well as an alp model based on a two higgs doublet model in the supplemental material. | xenon1t excess from anomaly-free axionlike dark matter and its implications for stellar cooling anomaly |
context. the observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. pds 70 is a young pre-main sequence star surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. this discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation.aims: we aim to characterize the orbital and atmospheric properties of pds 70 b, which was first identified on may 2015 in the course of the shine survey with sphere, the extreme adaptive-optics instrument at the vlt.methods: we obtained new deep sphere/irdis imaging and sphere/ifs spectroscopic observations of pds 70 b. the astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. for the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96-3.8 μm). we use different atmospheric models covering a large parameter space in temperature, log g, chemical composition, and cloud properties to characterize the properties of the atmosphere of pds 70 b.results: pds 70 b is most likely orbiting the star on a circular and disk coplanar orbit at 22 au inside the gap of the disk. we find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000-1600 k and log g no larger than 3.5 dex. the planet radius covers a relatively large range between 1.4 and 3.7 rj with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 myr.conclusions: this study provides a comprehensive data set on the orbital motion of pds 70 b, indicating a circular orbit and a motion coplanar with the disk. the first detailed spectral energy distribution of pds 70 b indicates a temperature typical of young giant planets. the detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux. based on observations collected at the european organisation for astronomical research in the southern hemisphere under eso programmes 095.c-0298, 097.c-0206, 097.c-1001, 1100.c-0481. | orbital and atmospheric characterization of the planet within the gap of the pds 70 transition disk |
gravitational potential fluctuations driven by bursty star formation can kinematically `heat up' dark matter at the centres of dwarf galaxies. a key prediction of such models is that, at a fixed dark matter halo mass, dwarfs with a higher stellar mass will have a lower central dark matter density. we use stellar kinematics and hi gas rotation curves to infer the inner dark matter densities of eight dwarf spheroidal and eight dwarf irregular galaxies with a wide range of star formation histories. for all galaxies, we estimate the dark matter density at a common radius of 150 pc, ρ _dm(150 pc). we find that our sample of dwarfs falls into two distinct classes. those that stopped forming stars over 6 gyr ago favour central densities ρ _dm(150 pc)> 10^8 m⊙ kpc-3, consistent with cold dark matter cusps, while those with more extended star formation favour ρ _dm(150 pc)< 10^8 m⊙ kpc-3, consistent with shallower dark matter cores. using abundance matching to infer pre-infall halo masses, m200, we show that this dichotomy is in excellent agreement with models in which dark matter is heated up by bursty star formation. in particular, we find that ρ _dm(150 pc) steadily decreases with increasing stellar mass-to-halo mass ratio, m*/m200. our results suggest that, to leading order, dark matter is a cold, collisionless, fluid that can be kinematically `heated up' and moved around. | dark matter heats up in dwarf galaxies |
one of the primary science goals of the next generation of hard x-ray timing instruments is to determine the equation of state of matter at supranuclear densities inside neutron stars by measuring the radius of neutron stars with different masses to accuracies of a few percent. three main techniques can be used to achieve this goal. the first involves waveform modeling. the flux observed from a hotspot on the neutron star surface offset from the rotational pole will be modulated by the star's rotation, and this periodic modulation at the spin frequency is called a pulsation. as the photons propagate through the curved spacetime of the star, information about mass and radius is encoded into the shape of the waveform (pulse profile) via special and general-relativistic effects. using pulsations from known sources (which have hotspots that develop either during thermonuclear bursts or due to channeled accretion) it is possible to obtain tight constraints on mass and radius. the second technique involves characterizing the spin distribution of accreting neutron stars. a large collecting area enables highly sensitive searches for weak or intermittent pulsations (which yield spin) from the many accreting neutron stars whose spin rates are not yet known. the most rapidly rotating stars provide a clean constraint, since the limiting spin rate where the equatorial surface velocity is comparable to the local orbital velocity, at which mass shedding occurs, is a function of mass and radius. however, the overall spin distribution also provides a guide to the torque mechanisms in operation and the moment of inertia, both of which can depend sensitively on dense matter physics. the third technique is to search for quasiperiodic oscillations in x-ray flux associated with global seismic vibrations of magnetars (the most highly magnetized neutron stars), triggered by magnetic explosions. the vibrational frequencies depend on stellar parameters including the dense matter equation of state, and large-area x-ray timing instruments would provide much improved detection capability. an illustration is given of how these complementary x-ray timing techniques can be used to constrain the dense matter equation of state and the results that might be expected from a 10 m2 instrument are discussed. also discussed are how the results from such a facility would compare to other astronomical investigations of neutron star properties. | colloquium: measuring the neutron star equation of state using x-ray timing |
the australian ska pathfinder (askap) telescope has started to localize fast radio bursts (frbs) to arcsecond accuracy from the detection of a single pulse, allowing their host galaxies to be reliably identified. we discuss the global properties of the host galaxies of the first four frbs localized by askap, which lie in the redshift range 0.11 < z < 0.48. all four are massive galaxies (log(m*/m⊙) ∼ 9.4-10.4) with modest star formation rates of up to 2 m⊙ yr-1—very different to the host galaxy of the first repeating frb 121102, which is a dwarf galaxy with a high specific star formation rate. the frbs localized by askap typically lie in the outskirts of their host galaxies, which appears to rule out frb progenitor models that invoke active galactic nuclei or free-floating cosmic strings. the stellar population seen in these host galaxies also disfavors models in which all frbs arise from young magnetars produced by superluminous supernovae, as proposed for the progenitor of frb 121102. a range of other progenitor models (including compact-object mergers and magnetars arising from normal core-collapse supernovae) remain plausible. | the host galaxies and progenitors of fast radio bursts localized with the australian square kilometre array pathfinder |
seven observations point towards the existence of primordial black holes (pbh), constituting the whole or an important fraction of the dark matter in the universe: the mass and spin of black holes detected by advanced ligo/virgo, the detection of micro-lensing events of distant quasars and stars in m31, the non-detection of ultra-faint dwarf satellite galaxies with radius below 15 parsecs, evidences for core galactic dark matter profiles, the correlation between x-ray and infrared cosmic backgrounds, and the existence of super-massive black holes very early in the universe's history. some of these hints are newly identified and they are all intriguingly compatible with the re-constructed broad pbh mass distribution from ligo events, peaking on pbh mass mpbh ≈ 3m⊙ and passing all other constraints on pbh abundances. pbh dark matter also provides a new mechanism to explain the mass-to-light ratios of dwarf galaxies, including the recent detection of a diffuse galaxy not dominated by dark matter. finally we conjecture that between 0.1% and 1% of the events detected by ligo will involve a pbh with a mass below the chandrasekhar mass, which would unambiguously prove the existence of pbh. | seven hints for primordial black hole dark matter |
it has been recently pointed out that a momentum-dependent coupling of the asymmetric dark matter (adm) with nucleons can explain the broad disagreement between helioseismological observables and the predictions of standard solar models. in this paper, we propose a minimal simplified adm model consisting of a scalar and a pseudoscalar mediator, in addition to a dirac fermionic dm, for generating such momentum-dependent interactions. remarkably, the pseudoscalar with mass around 750 gev can simultaneously explain the solar anomaly and the recent diphoton excess observed by both atlas and cms experiments in the early √{s }=13 tev lhc data. in this framework, the total width of the resonance is naturally large, as suggested by the atlas experiment, since the resonance mostly decays to the adm pair. the model predicts the existence of a new light scalar in the gev range, interacting with quarks, and observable dijet, monojet, and t t ¯ signatures for the 750 gev resonance at the lhc. | asymmetric dark matter in the sun and diphoton excess at the lhc |
alma observations have revealed the presence of dust in the first generations of galaxies in the universe. however, the dust temperature td remains mostly unconstrained due to the few available fir continuum data at redshift $z$ > 5. this introduces large uncertainties in several properties of high-$z$ galaxies, namely their dust masses, infrared luminosities, and obscured fraction of star formation. using a new method based on simultaneous [c $\scriptstyle \rm ii$] 158-μm line and underlying dust continuum measurements, we derive td in the continuum and [c $\scriptstyle \rm ii$] detected $z$ ≈ 7 galaxies in the alma large project rebels sample. we find 39 < td < 58 k, and dust masses in the narrow range md = (0.9-3.6) × 107 m⊙. these results allow us to extend for the first time the reported td($z$) relation into the epoch of reionization. we produce a new physical model that explains the increasing td($z$) trend with the decrease of gas depletion time, tdep = mg/sfr, induced by the higher cosmological accretion rate at early times; this hypothesis yields td ∝ (1 + $z$)0.4. the model also explains the observed td scatter at a fixed redshift. we find that dust is warmer in obscured sources, as a larger obscuration results in more efficient dust heating. for uv-transparent (obscured) galaxies, td only depends on the gas column density (metallicity), $t_{\rm d} \propto n_{\rm h}^{1/6}$ (td ∝ z-1/6). rebels galaxies are on average relatively transparent, with effective gas column densities around nh ≃ (0.03-1) × 1021 cm-2. we predict that other high-$z$ galaxies (e.g. macs0416-y1, a2744-yd4), with estimated td ≫ 60 k, are significantly obscured, low-metallicity systems. in fact, td is higher in metal-poor systems due to their smaller dust content, which for fixed lir results in warmer temperatures. | the alma rebels survey: cosmic dust temperature evolution out to z 7 |
we propose to develop a wide-field and ultra-high-precision photometric survey mission, temporarily named "earth 2.0 (et)". this mission is designed to measure, for the first time, the occurrence rate and the orbital distributions of earth-sized planets. et consists of seven 30cm telescopes, to be launched to the earth-sun's l2 point. six of these are transit telescopes with a field of view of 500 square degrees. staring in the direction that encompasses the original kepler field for four continuous years, this monitoring will return tens of thousands of transiting planets, including the elusive earth twins orbiting solar-type stars. the seventh telescope is a 30cm microlensing telescope that will monitor an area of 4 square degrees toward the galactic bulge. this, combined with simultaneous ground-based kmtnet observations, will measure masses for hundreds of long-period and free-floating planets. together, the transit and the microlensing telescopes will revolutionize our understandings of terrestrial planets across a large swath of orbital distances and free space. in addition, the survey data will also facilitate studies in the fields of asteroseismology, galactic archeology, time-domain sciences, and black holes in binaries. | et white paper: to find the first earth 2.0 |
in the present paper we obtain an anisotropic analog of the durgapal and fuloria (gen relativ gravit 17:671, 1985) perfect fluid solution. the methodology consists of contraction of the anisotropic factor with the help of both metric potentials and . here we consider the same as durgapal and fuloria (gen relativ gravit 17:671, 1985) did, whereas is as given by lake (phys rev d 67:104015, 2003). the field equations are solved by the change of dependent variable method. the solutions set mathematically thus obtained are compared with the physical properties of some of the compact stars, strange star as well as white dwarf. it is observed that all the expected physical features are available related to the stellar fluid distribution, which clearly indicates the validity of the model. | anisotropic models for compact stars |
context. in november 2019, erosita on board of the spektrum-roentgen-gamma (srg) observatory started to map the entire sky in x-rays. after the four-year survey program, it will reach a flux limit that is about 25 times deeper than rosat. during the srg performance verification phase, erosita observed a contiguous 140 deg2 area of the sky down to the final depth of the erosita all-sky survey (erosita final equatorial-depth survey; efeds), with the goal of obtaining a census of the x-ray emitting populations (stars, compact objects, galaxies, clusters of galaxies, and active galactic nuclei) that will be discovered over the entire sky.aims: this paper presents the identification of the counterparts to the point sources detected in efeds in the main and hard samples and their multi-wavelength properties, including redshift.methods: to identifyy the counterparts, we combined the results from two independent methods (nway and astromatch), trained on the multi-wavelength properties of a sample of 23k xmm-newton sources detected in the desi legacy imaging survey dr8. then spectroscopic redshifts and photometry from ancillary surveys were collated to compute photometric redshifts.results: of the efeds sources, 24 774 of 27 369 have reliable counterparts (90.5%) in the main sample and 231 of 246 sourcess (93.9%) have counterparts in the hard sample, including 2514 (3) sources for which a second counterpart is equally likely. by means of reliable spectra, gaia parallaxes, and/or multi-wavelength properties, we have classified the reliable counterparts in both samples into galactic (2695) and extragalactic sources (22 079). for about 340 of the extragalactic sources, we cannot rule out the possibility that they are unresolved clusters or belong to clusters. inspection of the distributions of the x-ray sources in various optical/ir colour-magnitude spaces reveal a rich variety of diverse classes of objects. the photometric redshifts are most reliable within the kids/viking area, where deep near-infrared data are also available.conclusions: this paper accompanies the erosita early data release of all the observations performed during the performance and verification phase. together with the catalogues of primary and secondary counterparts to the main and hard samples of the efeds survey, this paper releases their multi-wavelength properties and redshifts. the data are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/661/a3 | the erosita final equatorial-depth survey (efeds). identification and characterization of the counterparts to point-like sources |
estimates of the source parameters of gravitational-wave (gw) events produced by compact binary mergers rely on theoretical models for the gw signal. we present the first frequency-domain model for the inspiral, merger, and ringdown of the gw signal from precessing binary black hole systems that also includes multipoles beyond the leading-order quadrupole. our model, phenompv3hm, is a combination of the higher-multipole nonprecessing model phenomhm and the spin-precessing model phenompv3 that includes two-spin precession via a dynamical rotation of the gw multipoles. we validate the new model by comparing to a large set of precessing numerical-relativity simulations and find excellent agreement across the majority of the parameter space they cover. for mass ratios <5 the mismatch improves, on average, from ∼6 % to ∼2 % compared to phenompv3 when we include higher multipoles in the model. however, we find mismatches ∼8 % for a mass-ratio-6 and highly spinning simulation. we quantify the statistical uncertainty in the recovery of binary parameters by applying standard bayesian parameter estimation methods to simulated signals. we find that, while the primary black hole spin parameters should be measurable even at moderate signal-to-noise ratios (snrs) ∼30 , the secondary spin requires much larger snrs ∼200 . we also quantify the systematic uncertainty expected by recovering our simulated signals with different waveform models in which various physical effects—such as the inclusion of higher modes and/or precession—are omitted and find that even in the low-snr case (∼17 ) the recovered parameters can be biased. finally, as a first application of the new model we analyze the binary black hole event gw170729. we find larger values for the primary black hole mass of 58.25-12.53+11.73 m⊙ (90% credible interval). the lower limit (∼46 m⊙ ) is comparable to the proposed maximum black hole mass predicted by different stellar evolution models due to the pulsation pair-instability supernova (ppisn) mechanism. if we assume that the primary black hole in gw170729 formed through a ppisn, then out of the four ppisn models we consider only the model of woosley [1] is consistent with our mass measurements at the 90% confidence level. | including higher order multipoles in gravitational-wave models for precessing binary black holes |
the recently discovered gravitational wave sources gw190521 and gw190814 have shown evidence of bh mergers with masses and spins outside of the range expected from isolated stellar evolution. these merging objects could have undergone previous mergers. such hierarchical mergers are predicted to be frequent in active galactic nuclei (agns) disks, where binaries form and evolve efficiently by dynamical interactions and gaseous dissipation. here we compare the properties of these observed events to the theoretical models of mergers in agn disks, which are obtained by performing one-dimensional n-body simulations combined with semi-analytical prescriptions. the high bh masses in gw190521 are consistent with mergers of high-generation (high-g) bhs where the initial progenitor stars had high metallicity, 2g bhs if the original progenitors were metal-poor, or 1g bhs that had gained mass via super-eddington accretion. other measured properties related to spin parameters in gw190521 are also consistent with mergers in agn disks. furthermore, mergers in the lower mass gap or those with low mass ratio as found in gw190814 and gw190412 are also reproduced by mergers of 2g-1g or 1g-1g objects with significant accretion in agn disks. finally, due to gas accretion, the massive neutron star merger reported in gw190425 can be produced in an agn disk. | mass-gap mergers in active galactic nuclei |
star formation and supermassive black hole growth in galaxies appear to be self-limiting. the mechanisms for self-regulation are known as feedback. cosmic rays, the relativistic particle component of interstellar and intergalactic plasma, are among the agents of feedback. because cosmic rays are virtually collisionless in the plasma environments of interest, their interaction with the ambient medium is primarily mediated by large scale magnetic fields and kinetic scale plasma waves. because kinetic scales are much smaller than global scales, this interaction is most conveniently described by fluid models. in this paper, i discuss the kinetic theory and the classical theory of cosmic ray hydrodynamics (ccrh) which follows from assuming cosmic rays interact only with self-excited waves. i generalize ccrh to generalized cosmic ray hydrodynamics, which accommodates interactions with extrinsic turbulence, present examples of cosmic ray feedback, and assess where progress is needed. | the basis for cosmic ray feedback: written on the wind |
contents of gaia dr2: the five-parameter astrometric solution - positions on the sky (alpha,delta), parallaxes, and proper motions - for more than 1.3 billion (109) sources, with a limiting magnitude of g=21 and a bright limit of g~=3. parallax uncertainties are in the range of up to 0.04 milliarcsecond for sources at g<15, around 0.1mas for sources with g=17 and at the faint end, the uncertainty is of the order of 0.7mas at g=20. the corresponding uncertainties in the respective proper motion components are up to 0.06mas/yr (for g<15mag), 0.2mas/yr (for g=17mag) and 1.2mas/yr (for g=20mag). the gaia dr2 parallaxes and proper motions are based only on gaia data; they do no longer depend on the tycho-2 catalogue. median radial velocities (i.e. the median value over the epochs) for more than 6 million stars with a mean g magnitude between about 4 and 13 and an effective temperature (teff) in the range of about 3550 to 6900k. this leads to a full six-parameter solution: positions and motions on the sky with parallaxes and radial velocities, all combined with mean g magnitudes. the overall precision of the radial velocities at the bright end is in the order of 200-300m/s while at the faint end the overall precision is approximately 1.2km/s for a teff of 4750k and about 2.5km/s for a teff of 6500k. an additional set of more than 200 million sources for which a two-parameter solution is available: the positions on the sky (alpha,delta) combined with the mean g magnitude. these sources will have a positional uncertainty at g=20 of about 2mas, at j2015.5. g magnitudes for more than 1.5 billion sources, with precisions varying from around 1 milli-mag at the bright (g<13) end to around 20 milli-mag at g=20. please be aware that the photometric system for the g band in gaia dr2 will be different from the photometric system as used in gaia dr1. gbp and grp magnitudes for more than 1.1 billion sources, with precisions varying from a few milli-mag at the bright (g<13) end to around 200 milli-mag at g=20. full passband definitions for g, bp and rp. these passbands are now available for download. a detailed description is given here. epoch astrometry for more than 13,000 known asteroids based on more than 1.5 million ccd observations. 96% of the along-scan (al) residuals are in the range -5 to 5mas, and 52% of the al residuals are in the range of -1 to 1mas. the observations will be published in gaia dr2 and also delivered to the minor planet center (mpc). subject to limitations the effective temperatures teff for more than 150 million sources brighter than 17th magnitude with effective temperatures in the range 3000 to 10,000 k. for a subset of these sources also the line-of-sight extinction ag and reddening e(bp-rp) will be given, as well as the luminosity and radius. lightcurves for more than 500,000 variable sources consisting of cepheids, rr lyrae, mira and semi-regular candidates as well as high-amplitude delta scuti, by draconis candidates, sx phoenicis candidates and short time scale phenomena. planned cross-matches between gaia dr2 sources on the one hand and hipparcos-2, tycho-2, 2mass psc, sdss dr9, pan-starrs1, gsc2.3, ppm-xl, allwise, and urat-1 data on the other hand. catalogue of radial velocity standard stars (soubiran et al., 2018a&a...616a...7s): individual and combined radial velocity measurements are presented for 4813 stars in rvstdcat.dat and rvstdmes.dat files. (20 data files). | vizier online data catalog: gaia dr2 (gaia collaboration, 2018) |
gaia data release 3 provides novel flux-calibrated low-resolution spectrophotometry for ≃220 million sources in the wavelength range 330 nm ≤ λ ≤ 1050 nm (xp spectra). synthetic photometry directly tied to a flux in physical units can be obtained from these spectra for any passband fully enclosed in this wavelength range. we describe how synthetic photometry can be obtained from xp spectra, illustrating the performance that can be achieved under a range of different conditions - for example passband width and wavelength range - as well as the limits and the problems affecting it. existing top-quality photometry can be reproduced within a few per cent over a wide range of magnitudes and colour, for wide and medium bands, and with up to millimag accuracy when synthetic photometry is standardised with respect to these external sources. some examples of potential scientific application are presented, including the detection of multiple populations in globular clusters, the estimation of metallicity extended to the very metal-poor regime, and the classification of white dwarfs. a catalogue providing standardised photometry for ≃2.2 × 108 sources in several wide bands of widely used photometric systems is provided (gaia synthetic photometry catalogue; gspc) as well as a catalogue of ≃105 white dwarfs with da/non-da classification obtained with a random forest algorithm (gaia synthetic photometry catalogue for white dwarfs; gspc-wd). | gaia data release 3. the galaxy in your preferred colours: synthetic photometry from gaia low-resolution spectra |
aerogel fibers have been recognized as the rising star in the fields of thermal insulation and wearable textiles. yet, the lack of functionalization in aerogel fibers limits their applications. herein, we report hygroscopic holey graphene aerogel fibers (licl@hgafs) with integrated functionalities of highly efficient moisture capture, heat allocation, and microwave absorption. licl@hgafs realize the water sorption capacity over 4.15 g g−1, due to the high surface area and high water uptake kinetics. moreover, the sorbent can be regenerated through both photo-thermal and electro-thermal approaches. along with the water sorption and desorption, licl@hgafs experience an efficient heat transfer process, with a heat storage capacity of 6.93 kj g−1. the coefficient of performance in the heating and cooling mode can reach 1.72 and 0.70, respectively. notably, with the entrapped water, licl@hgafs exhibit broad microwave absorption with a bandwidth of 9.69 ghz, good impedance matching, and a high attenuation constant of 585. in light of these findings, the multifunctional licl@hgafs open an avenue for applications in water harvest, heat allocation, and microwave absorption. this strategy also suggests the possibility to functionalize aerogel fibers towards even broader applications. | hygroscopic holey graphene aerogel fibers enable highly efficient moisture capture, heat allocation and microwave absorption |
context. data from the gaia satellite are revolutionising our understanding of the milky way. with every new data release, there is a need to update the census of open clusters.aims: we aim to conduct a blind, all-sky search for open clusters using 729 million sources from gaia dr3 down to magnitude g ∼ 20, creating a homogeneous catalogue of clusters including many new objects.methods: we used the hierarchical density-based spatial clustering of applications with noise (hdbscan) algorithm to recover clusters. we validated our clusters using a statistical density test and a bayesian convolutional neural network for colour-magnitude diagram classification. we inferred basic astrometric parameters, ages, extinctions, and distances for the clusters in the catalogue.results: we recovered 7167 clusters, 2387 of which are candidate new objects and 4782 of which crossmatch to objects in the literature, including 134 globular clusters. a more stringent cut of our catalogue contains 4105 highly reliable clusters, 739 of which are new. owing to the scope of our methodology, we are able to tentatively suggest that many of the clusters we are unable to detect may not be real, including 1152 clusters from the milky way star cluster (mwsc) catalogue that should have been detectable in gaia data. our cluster membership lists include many new members and often include tidal tails. our catalogue's distribution traces the galactic warp, the spiral arm structure, and the dust distribution of the milky way. while much of the content of our catalogue contains bound open and globular clusters, as many as a few thousand of our clusters are more compatible with unbound moving groups, which we will classify in an upcoming work.conclusions: we have conducted the largest search for open clusters to date, producing a single homogeneous star cluster catalogue which we make available with this paper. full tables 3, b.1, and the cluster members (appendix a) are only available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/673/a114 | improving the open cluster census. ii. an all-sky cluster catalogue with gaia dr3 |
we evaluate the redshift distribution of binary black hole (bbh), black hole-neutron star binary (bhns), and binary neutron star (bns) mergers, exploring the main sources of uncertainty: star formation rate (sfr) density, metallicity evolution, common envelope, mass transfer via roche lobe overflow, natal kicks, core-collapse supernova model, and initial mass function. among binary evolution processes, uncertainties on common envelope ejection have a major impact: the local merger rate density of bnss varies from ∼103 to ∼20 gpc-3 yr-1 if we change the common envelope efficiency parameter from αce = 7 to 0.5, while the local merger rates of bbhs and bhnss vary by a factor of ∼2-3. the bbh merger rate changes by one order of magnitude, when 1σ uncertainties on metallicity evolution are taken into account. in contrast, the bns merger rate is almost insensitive to metallicity. hence, bnss are the ideal test bed to put constraints on uncertain binary evolution processes, such as common envelope and natal kicks. only models assuming values of αce ≳ 2 and moderately low natal kicks (depending on the ejected mass and the supernovae mechanism), result in a local bns merger rate density within the 90 per cent credible interval inferred from the second gravitational-wave transient catalogue. | the cosmic merger rate density of compact objects: impact of star formation, metallicity, initial mass function, and binary evolution |
aims: we present a 69 arcmin2 alma survey at 1.1 mm, goods-alma, matching the deepest hst-wfc3 h-band part of the goods-south field.methods: we tapered the 0″24 original image with a homogeneous and circular synthesized beam of 0″60 to reduce the number of independent beams - thus reducing the number of purely statistical spurious detections - and optimize the sensitivity to point sources. we extracted a catalog of galaxies purely selected by alma and identified sources with and without hst counterparts down to a 5σ limiting depth of h = 28.2 ab (hst/wfc3 f160w).results: alma detects 20 sources brighter than 0.7 mjy at 1.1 mm in the 0″60 tapered mosaic (rms sensitivity σ ≃ 0.18 mjy beam-1) with a purity greater than 80%. among these detections, we identify three sources with no hst nor spitzer-irac counterpart, consistent with the expected number of spurious galaxies from the analysis of the inverted image; their definitive status will require additional investigation. we detect additional three sources with hst counterparts either at high significance in the higher resolution map, or with different detection-algorithm parameters ensuring a purity greater than 80%. hence we identify in total 20 robust detections.conclusions: our wide contiguous survey allows us to push further in redshift the blind detection of massive galaxies with alma with a median redshift of z = 2.92 and a median stellar mass of m⋆ = 1.1 × 1011 m⊙. our sample includes 20% hst-dark galaxies (4 out of 20), all detected in the mid-infrared with spitzer-irac. the near-infrared based photometric redshifts of two of them (z ∼ 4.3 and 4.8) suggest that these sources have redshifts z > 4. at least 40% of the alma sources host an x-ray agn, compared to ∼14% for other galaxies of similar mass and redshift. the wide area of our alma survey provides lower values at the bright end of number counts than single-dish telescopes affected by confusion. | goods-alma: 1.1 mm galaxy survey. i. source catalog and optically dark galaxies |
the environment of actively repeating fast radio bursts (frbs) has been shown to be complex and varying. the recently localized frb 20190520b is extremely active, has the largest confirmed host dispersion measure, and is only the second frb source associated with a compact, persistent radio source (prs). the main tracer of the magneto-ionic environments is the rotation measure (rm), a path-integral of the line-of-sight component of magnetic field strength (b) and electron density, which does not allow a direct probe of the b-field configuration. here we report direct evidence for a b-field reversal based on the observed sign change and extreme variation of frb 20190520b's rm, which changed from $\sim10000$ rad m$^{-2}$ to $\sim-16000$ rad m$^{-2}$ between june 2021 and january 2022. such extreme rm reversal has never been observed before in any frb nor in any astronomical object. the implied short-term change of the b-field configuration in or around the frb could be due to the vicinity of massive black holes, or a magnetized companion star in binary systems, or a young supernova remnant along the line of sight. | magnetic field reversal around an active fast radio burst |
tianqin and lisa are space-based laser interferometer gravitational wave (gw) detectors planned to be launched in the mid-2030s. both detectors will detect low-frequency gws around $10^{-2}\,{\rm hz}$, however, tianqin is more sensitive to frequencies above this common sweet-spot while lisa is more sensitive to frequencies below $10^{-2}\,{\rm hz}$. therefore, tianqin and lisa will be able to detect the same sources but with different accuracy depending on the source and its parameters. we consider some of the most important astrophysical sources -- massive black hole binaries, stellar-mass black hole binaries, double white dwarfs, extreme mass ratio inspirals, light and heavy intermediate mass ratio inspirals, as well as the stochastic gravitational background of astrophysical origin -- that tianqin and lisa will be able to detect. for each of these sources, we analyze how far they can be detected (detection distance) and how well their parameters can be measured (detection accuracy) using a fisher matrix analysis. we compare the results obtained by the three detection scenarios (tianqin alone, lisa alone, and joint detection by lisa and tianqin) highlighting the gains from joint detection as well as the contribution of tianqin and lisa to a combined study of astrophysical sources. in particular, we consider the different orientations, lifetimes, and duty cycles of the two detectors to explore how they can give a more complete picture when working together. | detection of astrophysical gravitational wave sources by tianqin and lisa |
context. it has become clear in recent years that binarity plays a crucial role in many aspects of planetary nebulae (pne), particularly with regard to the striking morphologies they exhibit. to date, there are nearly 60 known binary central stars of pne (bcspne). however, both theory and observation indicate that this figure represents only the tip of the iceberg, with the galactic pn population hosting orders of magnitude more stars.aims: we are involved in a search for new bcspne with the aim of enhancing the statistical validation of the key role of binarity in the formation and shaping of pne. new discoveries of bcspne and their characterization carry important implications not only for understanding pn evolution, but also for studying binary evolution and the common-envelope phase, which is still poorly understood.methods: we used data from the tess satellite to search for variability in the eight cspne that belong to the two-minute cadence of preselected targets in cycle 1, with their available pipeline-extracted light curves. we identified strong periodicities and analysed them in the context of the binary scenario.results: all the cspne but one (abell 15) show clear signs of periodic variability in tess. the cause of this variability can be attributed to different effects, some of them requiring the presence of a companion star. we find simple sinusoidal modulations in several of the systems, compatible with irradiation effects. in addition, two of the central stars (pg 1034+001 and ngc 5189) also show photometric variations due to ellipsoidal variations and other signs of variability that are probably caused by star spots or relativistic doppler-beaming. the case of the well-studied helix nebula is of particular interest; here we constructed a series of binary models to explain the modulations we see in the light curve. we find that the variability constrains the possible companion to be very low-mass main-sequence star or sub-stellar object. we also identify, in substantial detail, the individual pulsation frequencies of ngc 246. | planetary nebulae seen with tess: discovery of new binary central star candidates from cycle 1 |
we present the first open gravitational-wave catalog, obtained by using the public data from advanced ligo’s first observing run to search for compact-object binary mergers. our analysis is based on new methods that improve the separation between signals and noise in matched-filter searches for gravitational waves from the merger of compact objects. the three most significant signals in our catalog correspond to the binary black hole mergers gw150914, gw151226, and lvt151012. we assume a common population of binary black holes for these three signals by defining a region of parameter space that is consistent with these events. under this assumption, we find that lvt151012 has a 97.6% probability of being astrophysical in origin. no other significant binary black hole candidates are found, nor did we observe any significant binary neutron star or neutron star-black hole candidates. we make available our complete catalog of events, including the subthreshold population of candidates. | 1-ogc: the first open gravitational-wave catalog of binary mergers from analysis of public advanced ligo data |
we present a model for the interaction of the gd-1 stellar stream with a massive perturber that naturally explains many of the observed stream features, including a gap and an off-stream spur of stars. the model involves an impulse by a fast encounter, after which the stream grows a loop of stars at different orbital energies. at specific viewing angles, this loop appears offset from the stream track. a quantitative comparison of the spur-and-gap features prefers models where the perturber is in the mass range of 106 -108 m ⊙. orbit integrations back in time show that the stream encounter could not have been caused by any known globular cluster or dwarf galaxy with a determined orbit, and mass, size, and impact parameter arguments show that it could not have been caused by a molecular cloud in the milky way disk. the most plausible explanation for the gap-and-spur structure is an encounter with a dark matter substructure, like those predicted to populate galactic halos in λcdm cosmology. however, the expected densities of λcdm subhalos in this mass range and in this part of the milky way are 2σ-3σ lower than the inferred density of the gd-1 perturber. this observation opens up the possibility that detailed observations of streams could measure the mass spectrum of dark matter substructures and even identify individual substructures and their orbits in the galactic halo. | the spur and the gap in gd-1: dynamical evidence for a dark substructure in the milky way halo |
gravitational-wave observations by the laser interferometer gravitational-wave observatory (ligo) and virgo have provided us a new tool to explore the universe on all scales from nuclear physics to the cosmos and have the massive potential to further impact fundamental physics, astrophysics, and cosmology for decades to come. in this paper we have studied the science capabilities of a network of ligo detectors when they reach their best possible sensitivity, called a#, given the infrastructure in which they exist and a new generation of observatories that are factor of 10 to 100 times more sensitive (depending on the frequency), in particular a pair of l-shaped cosmic explorer observatories (one 40 km and one 20 km arm length) in the us and the triangular einstein telescope with 10 km arms in europe. the presence of one or two a# observatories in a network containing two or one next generation observatories, respectively, will provide good localization capabilities for facilitating multimessenger astronomy and precision measurement of the hubble parameter. two cosmic explorer observatories are indispensable for achieving precise localization of binary neutron star events, facilitating detection of electromagnetic counterparts and transforming multimessenger astronomy. their combined operation is even more important in the detection and localization of high-redshift sources, such as binary neutron stars, beyond the star-formation peak, and primordial black hole mergers, which may occur roughly 100 million years after the big bang. the addition of the einstein telescope to a network of two cosmic explorer observatories is critical for accomplishing all the identified science metrics. for most metrics the triple network of next generation terrestrial observatories are a factor 100 better than what can be accomplished by a network of three a# observatories. | characterizing gravitational wave detector networks: from a$^\\sharp$ to cosmic explorer |
a gravitational-wave (gw) transient was identified in data recorded by the advanced laser interferometer gravitational-wave observatory (ligo) detectors on 2015 september 14. the event, initially designated g184098 and later given the name gw150914, is described in detail elsewhere. by prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, x-ray, and gamma-ray wavelengths with ground- and space-based facilities. in this letter we describe the low-latency analysis of the gw data and present the sky localization of the first observed compact binary merger. we summarize the follow-up observations reported by 25 teams via private gamma-ray coordinates network circulars, giving an overview of the participating facilities, the gw sky localization coverage, the timeline, and depth of the observations. as this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (em) signature. nevertheless, this first broadband campaign to search for a counterpart of an advanced ligo source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. detailed investigations of the em data and results of the em follow-up campaign are being disseminated in papers by the individual teams. | localization and broadband follow-up of the gravitational-wave transient gw150914 |
accurate line lists are crucial for correctly modelling a variety of astrophysical phenomena, including stellar photospheres and the atmospheres of extrasolar planets. this paper presents a new line database toto for the main isotopologues of titanium oxide (tio): ^{46}ti^{16}o, ^{47}ti^{16}o, ^{48}ti^{16}o, ^{49}ti^{16}o, and ^{50}ti^{16}o. the ^{48}ti^{16}o line list contains transitions with wave-numbers up to 30 000 cm-1, i.e. longwards of 0.33 μm. the toto line list includes all dipole-allowed transitions between 13 low-lying electronic states (x 3δ, a1δ, d 1σ+, e 3π, a 3φ, b3π, c 3δ, b 1π, c1φ, f1δ, e 1σ+). ab initio potential energy curves (pecs) are computed at the icmrci level and combined with spin-orbit and other coupling curves. these pecs and couplings are iteratively refined to match known empirical energy levels. accurate line intensities are generated using ab initio dipole moment curves. the toto line lists are appropriate for temperatures below 5000 k and contain 30 million transitions for ^{48}ti^{16}o; it is made available in electronic form via the cds data centre and via www.exomol.com. tests of the line lists show greatly improved agreement with observed spectra for objects such as m-dwarfs gj876 and gl581. | exomol molecular line lists - xxxiii. the spectrum of titanium oxide |
with the first detection of gravitational waves from a binary system of neutron stars gw170817, a new window was opened to study the properties of matter at and above nuclear-saturation density. reaching densities a few times that of nuclear matter and temperatures up to 100 mev, such mergers also represent potential sites for a phase transition (pt) from confined hadronic matter to deconfined quark matter. while the lack of a postmerger signal in gw170817 has prevented us from assessing experimentally this scenario, two theoretical studies have explored the postmerger gravitational-wave signatures of pts in mergers of a binary system of neutron stars. we here extend and complete the picture by presenting a novel signature of the occurrence of a pt. more specifically, using fully general-relativistic hydrodynamic simulations and employing a suitably constructed equation of state that includes a pt, we present the occurrence of a "delayed pt," i.e., a pt that develops only some time after the merger and produces a metastable object with a quark-matter core, i.e., a hypermassive hybrid star. because in this scenario, the postmerger signal exhibits two distinct fundamental gravitational-wave frequencies—before and after the pt—the associated signature promises to be the strongest and cleanest among those considered so far, and one of the best signatures of the production of quark matter in the present universe. | postmerger gravitational-wave signatures of phase transitions in binary mergers |
candidates for the modest galaxies that formed most of the stars in the early universe, at redshifts z > 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging. but it has proved difficult for existing spectrographs to characterize them using their ultraviolet light. the detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. so far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z >= 7. here we report thermal dust emission from an archetypal early universe star-forming galaxy, a1689-zd1. we detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 +/- 0.2 from a spectroscopic detection of the lyman-α break. a1689-zd1 is representative of the star-forming population during the epoch of reionization, with a total star-formation rate of about 12 solar masses per year. the galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the milky way. dusty, evolved galaxies are thus present among the fainter star-forming population at z > 7. | a dusty, normal galaxy in the epoch of reionization |
the sdss-iv apache point observatory galactic evolution experiment (apogee) survey has obtained high-resolution spectra for thousands of red giant stars distributed among the massive satellite galaxies of the milky way (mw): the large and small magellanic clouds (lmc/smc), the sagittarius dwarf galaxy (sgr), fornax (fnx), and the now fully disrupted gaia sausage/enceladus (gse) system. we present and analyze the apogee chemical abundance patterns of each galaxy to draw robust conclusions about their star formation histories, by quantifying the relative abundance trends of multiple elements (c, n, o, mg, al, si, ca, fe, ni, and ce), as well as by fitting chemical evolution models to the [α/fe]-[fe/h] abundance plane for each galaxy. results show that the chemical signatures of the starburst in the magellanic clouds (mcs) observed by nidever et al. in the α-element abundances extend to c+n, al, and ni, with the major burst in the smc occurring some 3-4 gyr before the burst in the lmc. we find that sgr and fnx also exhibit chemical abundance patterns suggestive of secondary star formation epochs, but these events were weaker and earlier (~5-7 gyr ago) than those observed in the mcs. there is no chemical evidence of a second starburst in gse, but this galaxy shows the strongest initial star formation as compared to the other four galaxies. all dwarf galaxies had greater relative contributions of agb stars to their enrichment than the mw. comparing and contrasting these chemical patterns highlight the importance of galaxy environment on its chemical evolution. | apogee chemical abundance patterns of the massive milky way satellites |
we combine the equation of state of dense matter up to twice nuclear saturation density nsat obtained using chiral effective field theory (χ eft ) and recent observations of neutron stars to gain insights about the high-density matter encountered in their cores. a key element in our study is the recent bayesian analysis of correlated eft truncation errors based on order-by-order calculations up to next-to-next-to-next-to-leading order in the χ eft expansion. we refine the bounds on the maximum mass imposed by causality at high densities and provide stringent limits on the maximum and minimum radii of ∼1.4 m⊙ and ∼2.0 m⊙ stars. including χ eft predictions from nsat to 2 nsat reduces the permitted ranges of the radius of a 1.4 m⊙ star, r1.4, by ∼3.5 km . if observations indicate r1.4<11.2 km , then our study implies that either the squared speed of sound cs2>1 /2 for densities above 2 nsat or that χ eft breaks down below 2 nsat . we also comment on the nature of the secondary compact object in gw190814 with mass ≃2.6 m⊙ and discuss the implications of massive neutron stars >2.1 m⊙(2.6 m⊙) in future radio and gravitational-wave searches. some form of strongly interacting matter with cs2>0.35 (0.55 ) must be realized in the cores of such massive neutron stars. in the absence of phase transitions below 2 nsat , the small tidal deformability inferred from gw170817 lends support for the relatively small pressure predicted by χ eft for the baryon density nb in the range 1 -2 nsat . together they imply that the rapid stiffening required to support a high maximum mass should occur only when nb≳1.5 -1.8 nsat . | limiting masses and radii of neutron stars and their implications |
in 2007, a very bright radio pulse was identified in the archival data of the parkes telescope in australia, marking the beginning of a new research branch in astrophysics. in 2013, this kind of millisecond bursts with extremely high brightness temperature takes a unified name, fast radio burst (frb). over the first few years, frbs seemed very mysterious because the sample of known events was limited. with the improvement of instruments over the last five years, hundreds of new frbs have been discovered. the field is now undergoing a revolution and understanding of frb has rapidly increased as new observational data increasingly accumulate. in this review, we will summarize the basic physics of frbs and discuss the current research progress in this area. we have tried to cover a wide range of frb topics, including the observational property, propagation effect, population study, radiation mechanism, source model, and application in cosmology. a framework based on the latest observational facts is now under construction. in the near future, this exciting field is expected to make significant breakthroughs. | the physics of fast radio bursts |
we present a novel implementation of supermassive black hole (smbh) formation, dynamics and accretion in the massively parallel tree+sph code, changa. this approach improves the modelling of smbhs in fully cosmological simulations, allowing for a more detailed analysis of smbh-galaxy co-evolution throughout cosmic time. our scheme includes novel, physically motivated models for smbh formation, dynamics and sinking timescales within galaxies and smbh accretion of rotationally supported gas. the sub-grid parameters that regulate star formation (sf) and feedback from smbhs and sne are optimized against a comprehensive set of z = 0 galaxy scaling relations using a novel, multidimensional parameter search. we have incorporated our new smbh implementation and parameter optimization into a new set of high-resolution, large-scale cosmological simulations called romulus. we present initial results from our flagship simulation, romulus25, showing that our smbh model results in sf efficiency, smbh masses and global sf and smbh accretion histories at high redshift that are consistent with observations. we discuss the importance of smbh physics in shaping the evolution of massive galaxies and show how smbh feedback is much more effective at regulating sf compared to sne feedback in this regime. further, we show how each aspect of our smbh model impacts this evolution compared to more common approaches. finally, we present a science application of this scheme studying the properties and time evolution of an example dual active galactic nucleus system, highlighting how our approach allows simulations to better study galaxy interactions and smbh mergers in the context of galaxy-bh co-evolution. | the romulus cosmological simulations: a physical approach to the formation, dynamics and accretion models of smbhs |
the high-energy emission from low-mass stars is mediated by the magnetic dynamo. although the mechanisms by which fully convective stars generate large-scale magnetic fields are not well understood, it is clear that, as for solar-type stars, stellar rotation plays a pivotal role. we present 270 new optical spectra of low-mass stars in the solar neighborhood. combining our observations with those from the literature, our sample comprises 2202 measurements or non-detections of hα emission in nearby m dwarfs. this includes 466 with photometric rotation periods. stars with masses between 0.1 and 0.6 m⊙ are well-represented in our sample, with fast and slow rotators of all masses. we observe a threshold in the mass-period plane that separates active and inactive m dwarfs. the threshold coincides with the fast-period edge of the slowly rotating population, at approximately the rotation period at which an era of rapid rotational evolution appears to cease. the well-defined active/inactive boundary indicates that hα activity is a useful diagnostic for stellar rotation period, e.g., for target selection for exoplanet surveys, and we present a mass-period relation for inactive m dwarfs. we also find a significant, moderate correlation between lhα/lbol and variability amplitude: more active stars display higher levels of photometric variability. consistent with previous work, our data show that rapid rotators maintain a saturated value of lhα/lbol. our data also show a clear power-law decay in lhα/lbol with rossby number for slow rotators, with an index of -1.7 ± 0.1. | the hα emission of nearby m dwarfs and its relation to stellar rotation |
in a star cluster with a sufficiently large escape velocity, black holes (bhs) that are produced by bh mergers can be retained, dynamically form new bh binaries, and merge again. this process can repeat several times and lead to significant mass growth. in this paper, we calculate the mass of the largest bh that can form through repeated bh mergers and determine how its value depends on the physical properties of the host cluster. we adopt an analytical model in which the energy generated by the black hole binaries in the cluster core is assumed to be regulated by the process of two-body relaxation in the bulk of the system. this principle is used to compute the hardening rate of the binaries and to relate this to the time-dependent global properties of the parent cluster. we demonstrate that in clusters with initial escape velocity {≳ } 300 {km s}^{-1} in the core and density {≳ } 10^5 m_⊙ pc^{-3}, repeated mergers lead to the formation of bhs in the mass range 100-10^5 m_⊙, populating any upper mass gap created by pair-instability supernovae. this result is independent of cluster metallicity and the initial bh spin distribution. we show that about 10{{ per cent}} of the present-day nuclear star clusters meet these extreme conditions, and estimate that bh binary mergers with total mass {≳ } 100 m _⊙ should be produced in these systems at a maximum rate {≈ } 0.05 gpc^{-3} yr^{-1}, corresponding to one detectable event every few years with advanced ligo/virgo at design sensitivity. | black hole growth through hierarchical black hole mergers in dense star clusters: implications for gravitational wave detections |
we investigate the inner regions of the milky way using data from apogee and gaia edr3. our inner galactic sample has more than 26 500 stars within |xgal|< 5 kpc, |ygal|< 3.5 kpc, |zgal|< 1 kpc, and we also carry out the analysis for a foreground-cleaned subsample of 8000 stars that is more representative of the bulge-bar populations. these samples allow us to build chemo-dynamical maps of the stellar populations with vastly improved detail. the inner galaxy shows an apparent chemical bimodality in key abundance ratios [α/fe], [c/n], and [mn/o], which probe different enrichment timescales, suggesting a star formation gap (quenching) between the high- and low-α populations. using a joint analysis of the distributions of kinematics, metallicities, mean orbital radius, and chemical abundances, we can characterize the different populations coexisting in the innermost regions of the galaxy for the first time. the chemo-kinematic data dissected on an eccentricity-|z|max plane reveal the chemical and kinematic signatures of the bar, the thin inner disc, and an inner thick disc, and a broad metallicity population with large velocity dispersion indicative of a pressure-supported component. the interplay between these different populations is mapped onto the different metallicity distributions seen in the eccentricity-|z|max diagram consistently with the mean orbital radius and vϕ distributions. a clear metallicity gradient as a function of |z|max is also found, which is consistent with the spatial overlapping of different populations. additionally, we find and chemically and kinematically characterize a group of counter-rotating stars that could be the result of a gas-rich merger event or just the result of clumpy star formation during the earliest phases of the early disc that migrated into the bulge. finally, based on 6d information, we assign stars a probability value of being on a bar orbit and find that most of the stars with large bar orbit probabilities come from the innermost 3 kpc, with a broad dispersion of metallicity. even stars with a high probability of belonging to the bar show chemical bimodality in the [α/fe] versus [fe/h] diagram. this suggests bar trapping to be an efficient mechanism, explaining why stars on bar orbits do not show a significant, distinct chemical abundance ratio signature. | the milky way bar and bulge revealed by apogee and gaia edr3 |
we consider radio bursts that originate from extragalactic neutron stars (nss) by addressing three questions about source distances. what are the physical limitations on coherent radiation at ghz frequencies? do they permit detection at cosmological distances? how many bursts per ns are needed to produce the inferred burst rate ∼103-104sky-1 d-1? the burst rate is comparable to the ns formation rate in a hubble volume, requiring only one per ns if they are bright enough. radiation physics suggests a closer population, requiring more bursts per ns and increasing the chances for repeats. bursts comprise sub-ns, coherent shot pulses superposed incoherently to produce ms-duration ∼1 jy amplitudes; each shot pulse can be much weaker than 1 jy, placing less restrictive requirements on the emission process. none the less, single shot pulses are similar to the extreme, unresolved (<0.4 ns) mjy shot pulse seen from the crab pulsar, consistent with coherent curvature radiation emitted near the light cylinder by an almost neutral clump with net charge ∼± 1021e and total energy ≳ 1023 erg. bursts from gpc distances require incoherent superposition of {∼ } 10^{12}d_gpc^2 shot pulses or a total energy ≳ 10^{35} d_gpc^2 erg. the energy reservoir near the light cylinder limits the detection distance to ≲ few × 100 mpc for a fluence ∼1 jy ms unless conditions are more extreme than for the crab pulsar, such as in magnetars. we discuss contributions to dispersion measures from galaxy clusters and we propose tests for the overall picture presented. | supergiant pulses from extragalactic neutron stars |
i present an analysis of the jwst nirspec data of smacs 0723 released as early release observations. as part of this three new redshifts are provided, bringing the total of reliable redshifts to 14. i propose a modification to the direct abundance determination method that reduces sensitivity to flux calibration uncertainties by a factor of ~3 and show that the resulting abundances are in good agreement with bayesian photoionization models of the rest-frame optical spectrum. i also show that 6355 is most likely a narrow-line active galactic nucleus (agn) with $m_*\lt 10^9\, \mathrm{m}_\odot$ at z = 7.66 and argue that 10 612 might also have an agn contribution to its flux through comparison to photoionization models and low-redshift analogues. under the assumption that the lines come from star formation, i find that the galaxies have gas depletion times of ~107 yr, comparable to similar galaxies locally. i also identify a population of possibly shock-dominated galaxies at z < 3, whose near-ir emission lines plausibly come nearly all from shocks and discuss their implications. i close with a discussion of the potential for biases in the determination of the mass-metallicity relation using samples defined by detected [o iii]4363 and show using low-z galaxies that this can lead to biases of up to 0.5 dex with a systematic trend with mass. | high-z galaxies with jwst and local analogues - it is not only star formation |
the ultraviolet (uv) continuum slope (β, where fλ∝ λβ ) of galaxies is sensitive to a variety of properties, from the metallicity and age of the stellar population to dust attenuation throughout the galaxy. considerable attention has focused on identifying reionization-era galaxies with very blue uv slopes (β < -3). not only do such systems provide a signpost of low-metallicity stars, but they also identify galaxies likely to leak ionizing photons from their h ii regions as such blue uv slopes require the reddening effect of nebular continuum to be diminished. in this paper we present a search for reionization-era galaxies with very blue uv colors in recent jwst/nircam imaging of the extended groth strip field. we characterize uv slopes for a large sample of z ≃ 7-11 galaxies, finding a median of β = -2.0. two lower luminosity (m uv ≃ -19.5) and lower stellar mass (6-10 × 107 m ⊙) systems exhibit extremely blue uv slopes (β = -2.9 to -3.1) and rest-optical photometry indicating weak nebular line emission. each system is very compact (re≲ 260 pc) with very high star formation-rate surface densities. we model the spectral energy distributions (seds) with a suite of beagle models with varying levels of ionizing photon escape. the seds cannot be reproduced with our fiducial (f esc,h ii= 0) or alpha-enhanced (z ⋆ < z ism) models. the combined blue uv slopes and weak nebular emission are best-fit by models with significant ionizing photon escape from h ii regions (f esc,h ii= 0.5-0.8) and extremely low-metallicity massive stars (z ⋆ = 0.01-0.06 z ⊙). the discovery of these galaxies highlights the potential for jwst to identify large numbers of candidate lyman continuum leaking galaxies in the reionization era and suggests low-metallicity stellar populations may be common in dwarf galaxies at z > 7. | searching for extremely blue uv continuum slopes at z = 7-11 in jwst/nircam imaging: implications for stellar metallicity and ionizing photon escape in early galaxies |
we describe the milky way survey (mws) that will be undertaken with the dark energy spectroscopic instrument (desi) on the mayall 4 m telescope at the kitt peak national observatory. over the next 5 yr desi mws will observe approximately seven million stars at galactic latitudes |b| > 20°, with an inclusive target selection scheme focused on the thick disk and stellar halo. mws will also include several high-completeness samples of rare stellar types, including white dwarfs, low-mass stars within 100 pc of the sun, and horizontal branch stars. we summarize the potential of desi to advance understanding of the galactic structure and stellar evolution. we introduce the final definitions of the main mws target classes and estimate the number of stars in each class that will be observed. we describe our pipelines for deriving radial velocities, atmospheric parameters, and chemical abundances. we use ≃500,000 spectra of unique stellar targets from the desi survey validation program (sv) to demonstrate that our pipelines can measure radial velocities to ≃1 km s-1 and [fe/h] accurate to ≃0.2 dex for typical stars in our main sample. we find the stellar parameter distributions from ≈100 deg2 of sv observations with ≳90% completeness on our main sample are in good agreement with expectations from mock catalogs and previous surveys. | overview of the desi milky way survey |
the ligo scientific and virgo collaborations have announced the event gw170817, the first detection of gravitational waves from the coalescence of two neutron stars. the merger rate of binary neutron stars estimated from this event suggests that distant, unresolvable binary neutron stars create a significant astrophysical stochastic gravitational-wave background. the binary neutron star component will add to the contribution from binary black holes, increasing the amplitude of the total astrophysical background relative to previous expectations. in the advanced ligo-virgo frequency band most sensitive to stochastic backgrounds (near 25 hz), we predict a total astrophysical background with amplitude ωgw(f =25 hz )=1. 8-1.3+2.7×10-9 with 90% confidence, compared with ωgw(f =25 hz )=1. 1-0.7+1.2×10-9 from binary black holes alone. assuming the most probable rate for compact binary mergers, we find that the total background may be detectable with a signal-to-noise-ratio of 3 after 40 months of total observation time, based on the expected timeline for advanced ligo and virgo to reach their design sensitivity. | gw170817: implications for the stochastic gravitational-wave background from compact binary coalescences |
on 2019 august 14, the ligo and virgo detectors observed gw190814, a gravitational-wave signal originating from the merger of a $\simeq \,23\,{m}_{\odot }$ black hole (bh) with a $\simeq \,2.6\,{m}_{\odot }$ compact object. gw190814's compact-binary source is atypical both in its highly asymmetric masses and in its lower-mass component lying between the heaviest known neutron star (ns) and lightest known bh in a compact-object binary. if formed through isolated binary evolution, the mass of the secondary is indicative of its mass at birth. we examine the formation of such systems through isolated binary evolution across a suite of assumptions encapsulating many physical uncertainties in massive-star binary evolution. we update how mass loss is implemented for the neutronization process during the collapse of the proto-compact object to eliminate artificial gaps in the mass spectrum at the transition between nss and bhs. we find it challenging for population modeling to match the empirical rate of gw190814-like systems while simultaneously being consistent with the rates of other compact binary populations inferred from gravitational-wave observations. nonetheless, the formation of gw190814-like systems at any measurable rate requires a supernova engine model that acts on longer timescales such that the proto-compact object can undergo substantial accretion immediately prior to explosion, hinting that if gw190814 is the result of massive-star binary evolution, the mass gap between nss and bhs may be narrower or nonexistent. | exploring the lower mass gap and unequal mass regime in compact binary evolution |
while once rare, observations of stars being tidally disrupted by supermassive black holes are quickly becoming commonplace. to continue to learn from these events, it is necessary to robustly and systematically compare our growing number of observations with theory. we present a tidal disruption module for the modular open source fitter for transients (mosfit) and the results from fitting 14 tidal disruption events (tdes). our model uses flash simulations of tdes to generate bolometric luminosities and passes these luminosities through viscosity and reprocessing transformation functions to create multiwavelength light curves. it then uses an mcmc fitting routine to compare these theoretical light curves with observations. we find that none of the events show evidence for viscous delays exceeding a few days, supporting the theory that our current observing strategies in the optical/uv are missing a significant number of viscously delayed flares. we find that the events have black hole masses of 106-108 m ⊙ and that the masses we predict are as reliable as those based on bulk galaxy properties. we also find that there is a preference for stars with mass <1 m ⊙, as expected when low-mass stars greatly outnumber high-mass stars. | weighing black holes using tidal disruption events |
in this paper we review the current status of research on the observational and theoretical characteristics of isolated and binary magnetic white dwarfs (mwds). | magnetic white dwarfs |
we present a search for extremely red, dust-obscured, z > 7 galaxies with jwst/nircam+miri imaging over the first 20 arcmin2 of publicly available cycle 1 data from the cosmos-web, ceers, and primer surveys. based on their red color in f277w-f444w (~2.5 mag) and detection in miri/f770w (~25 mag), we identify two galaxies, cos-z8m1 and ceers-z7m1, that have best-fit photometric redshifts of $z={8.4}_{-0.4}^{+0.3}$ and ${7.6}_{-0.1}^{+0.1}$ , respectively. we perform spectral energy distribution fitting with a variety of codes (including bagpipes, prospector, beagle, and cigale) and find a >95% probability that these indeed lie at z > 7. both sources are compact (r eff ≲ 200 pc) and highly obscured (av~ 1.5-2.5) and, at our best-fit redshift estimates, likely have strong [o iii]+hβ emission contributing to their 4.4 μm photometry. we estimate stellar masses of ~1010 m ⊙ for both sources; by virtue of detection in miri at 7.7 μm, these measurements are robust to the inclusion of bright emission lines, for example, from an active galactic nucleus. we identify a marginal (2.9σ) atacama large millimeter/submillimeter array detection at 2 mm within 0.″5 of cos-z8m1, which, if real, would suggest a remarkably high ir luminosity of ~1012 l ⊙. these two galaxies, if confirmed at z ~ 8, would be extreme in their stellar and dust masses and may be representative of a substantial population of highly dust-obscured galaxies at cosmic dawn. | two massive, compact, and dust-obscured candidate z ≃ 8 galaxies discovered by jwst |
we present the star cluster hunting pipeline (ship) that can identify star clusters in gaia second data release (dr2) data and establish a star cluster catalog for the galactic disk. a friend-of-friend-based cluster finder method is used to identify star clusters using five-dimensional stellar parameters, l,b,\varpi ,{μ }α \cos δ , and μδ . our new catalog contains 2443 star cluster candidates identified from disk stars located within | b| =25^\circ and with g < 18 mag. an automatic isochrone fitting scheme is applied to all cluster candidates. with a combination of parameters obtained from isochrone fitting, we classify cluster candidates into three classes (class 1, 2, and 3). class 1 clusters are the most probable star cluster candidates with the most stringent criteria. most of these clusters are nearby (within 4 kpc). our catalog is crossmatched with three galactic star cluster catalogs, kharchenko et al., gaudin et al., and bica et al. the proper motion and parallax of matched star clusters are in good agreement with these earlier catalogs. we discover 76 new star cluster candidates that are not listed in these three catalogs. the majority of these are clusters older than log(age/yr) = 8.0 and are located in the inner disk with | b| < 5^\circ . the recent discovery of new star clusters suggests that current galactic star cluster catalogs are still incomplete. among the class 1 cluster candidates, we find 56 candidates for star cluster groups. the pipeline, the catalog, and the member list containing all candidates star clusters and star cluster groups have been made publicly available. | a catalog of newly identified star clusters in gaia dr2 |
as the number of merging binary black holes observed with ground-based gravitational-wave detectors grows, increasingly accurate theoretical models are required to compare them to the observed sample and disentangle contributions from multiple channels. in formation models involving isolated binary stars, important uncertainties remain regarding the stability of mass transfer and common-envelope evolution. to study some of these uncertainties, we have computed binary simulations using the mesa code consisting of a 30 m⊙ star in a low metallicity (z⊙/10) environment with a black-hole companion. we have developed an updated prescription to compute mass transfer rates including the possibility of outflows from outer lagrangian points, as well as a method to self-consistently determine the core-envelope boundary in cases where there is common-envelope evolution. we find that binaries survive common-envelope evolution only if unstable mass transfer happens after the formation of a deep convective envelope, resulting in a narrow range (0.2 dex) in period for successful envelope ejection. all cases where binary interaction is initiated with a radiative envelope have large binding energies (∼1050 erg), and they result in mergers during the common-envelope phase even under the assumption that all the internal and recombination energy of the envelope, as well as the energy from an inspiral, is used to eject the envelope. this is independent of whether or not helium is ignited in the core of the donor, conditions under which various rapid-population synthesis calculations assume a successful envelope ejection is possible. moreover, we find that the critical mass ratio for instability is such that across a large range in initial orbital periods (∼1−1000 days), merging binary black holes can be formed via stable mass transfer. a large fraction of these systems undergo overflow of their l2 equipotential, in which case we find that stable mass transfer produces merging binary black holes even under extreme assumptions of mass and angular momentum outflows. our conclusions are limited to the study of one donor mass at a single metallicity, but they suggest that population synthesis calculations overestimate the formation rate of merging binary black holes produced by common-envelope evolution and that stable mass transfer could dominate the formation rate from isolated binaries. this is in agreement with a few other recent studies. further work is required to extend these results to different masses and metallicities as well as to understand how they can be incorporated into rapid population synthesis calculations. | the role of mass transfer and common envelope evolution in the formation of merging binary black holes |
we present final spitzer trigonometric parallaxes for 361 l, t, and y dwarfs. we combine these with prior studies to build a list of 525 known l, t, and y dwarfs within 20 pc of the sun, 38 of which are presented here for the first time. using published photometry and spectroscopy as well as our own follow-up, we present an array of color-magnitude and color-color diagrams to further characterize census members, and we provide polynomial fits to the bulk trends. using these characterizations, we assign each object a teff value and judge sample completeness over bins of teff and spectral type. except for types ≥t8 and teff < 600 k, our census is statistically complete to the 20 pc limit. we compare our measured space densities to simulated density distributions and find that the best fit is a power law ( ${dn}/{dm}\propto {m}^{-\alpha }$ <!-- --> ) with α = 0.6 ± 0.1. we find that the evolutionary models of saumon & marley correctly predict the observed magnitude of the space density spike seen at 1200 k < teff < 1350 k, believed to be caused by an increase in the cooling timescale across the l/t transition. defining the low-mass terminus using this sample requires a more statistically robust and complete sample of dwarfs ≥y0.5 and with teff < 400 k. we conclude that such frigid objects must exist in substantial numbers, despite the fact that few have so far been identified, and we discuss possible reasons why they have largely eluded detection. | the field substellar mass function based on the full-sky 20 pc census of 525 l, t, and y dwarfs |
theoretical modeling of massive stars predicts a gap in the black hole (bh) mass function above ∼40-50 m⊙ for bhs formed through single star evolution, arising from (pulsational) pair-instability supernovae (pisne). however, in dense star clusters, dynamical channels may exist that allow construction of bhs with masses in excess of those allowed from single star evolution. the detection of bhs in this so-called "upper-mass gap" would provide strong evidence for the dynamical processing of bhs prior to their eventual merger. here, we explore in detail the formation of bhs with masses within or above the pair-instability gap through collisions of young massive stars in dense star clusters. we run a suite of 68 independent cluster simulations, exploring a variety of physical assumptions pertaining to growth through stellar collisions, including primordial cluster mass segregation and the efficiency of envelope stripping during collisions. we find that as many as ∼20% of all bh progenitors undergo one or more collisions prior to stellar collapse and up to ∼1% of all bhs reside within or above the pair-instability gap through the effects of these collisions. we show that these bhs readily go on to merge with other bhs in the cluster, creating a population of massive bh mergers at a rate that may compete with the "multiple-generation" merger channel described in other analyses. this has clear relevance for the formation of very massive bh binaries as recently detected by the laser interferometer gravitational-wave observatory/virgo in gw190521. finally, we describe how stellar collisions in clusters may provide a unique pathway to pisne and briefly discuss the expected rate of these events and other electromagnetic transients. | populating the upper black hole mass gap through stellar collisions in young star clusters |
three-body forces acting on a λ hyperon in a nuclear medium are investigated, with special focus on the so-called hyperon puzzle in neutron stars. the hyperon-nucleon two-body interaction deduced from su(3) chiral effective field theory is employed at next-to-leading order. hyperon-nucleon three-body forces are approximated using saturation by decuplet baryons and are transcribed to density-dependent effective two-body interactions. these together are taken as input in a brueckner-bethe-goldstone equation with explicit treatment of the λ n ↔σ n and λ n n ↔σ n n coupled channels. single-particle potentials of a λ hyperon in symmetric nuclear matter and neutron matter are calculated. with parameters of the λ n n three-body force constrained by hypernuclear phenomenology, extrapolations to high baryon density are performed. by comparison of the λ and neutron chemical potentials at densities characteristic of the core of neutron stars it is found that the combined repulsive effects of two- and three-body correlations can make the appearance of λ hyperons in neutron stars energetically unfavourable, thus potentially offering a possible answer to a longstanding query. | hyperon-nucleon three-body forces and strangeness in neutron stars |
context. clouds are ubiquitous in exoplanet atmospheres and they represent a challenge for the model interpretation of their spectra. when generating a large number of model spectra, complex cloud models often prove too costly numerically, whereas more efficient models may be overly simplified.aims: we aim to constrain the atmospheric properties of the directly imaged planet hr 8799e with a free retrieval approach.methods: we used our radiative transfer code petitradtrans for generating the spectra, which we coupled to the pymultinest tool. we added the effect of multiple scattering which is important for treating clouds. two cloud model parameterizations are tested: the first incorporates the mixing and settling of condensates, the second simply parameterizes the functional form of the opacity.results: in mock retrievals, using an inadequate cloud model may result in atmospheres that are more isothermal and less cloudy than the input. applying our framework on observations of hr 8799e made with the gpi, sphere, and gravity, we find a cloudy atmosphere governed by disequilibrium chemistry, confirming previous analyses. we retrieve that c/o = 0.60-0.08+0.07. other models have not yet produced a well constrained c/o value for this planet. the retrieved c/o values of both cloud models are consistent, while leading to different atmospheric structures: either cloudy or more isothermal and less cloudy. fitting the observations with the self-consistent exo-rem model leads to comparable results, without constraining c/o.conclusions: with data from the most sensitive instruments, retrieval analyses of directly imaged planets are possible. the inferred c/o ratio of hr 8799e is independent of the cloud model and thus appears to be a robust. this c/o is consistent with stellar, which could indicate that the hr 8799e formed outside the co2 or co iceline. as it is the innermost planet of the system, this constraint could apply to all hr 8799 planets. | retrieving scattering clouds and disequilibrium chemistry in the atmosphere of hr 8799e |
in this work, we present a new class of analytic and well-behaved solution to einstein's field equations describing anisotropic matter distribution. it's achieved in the embedding class one spacetime framework using karmarkar's condition. we perform our analysis by proposing a new metric potential grr which yields us a physically viable performance of all physical variables. the obtained model is representing the physical features of the solution in detail, analytically as well as graphically for strange star candidate sax j1808.4-3658 (m a s s =0.9 m⊙ , r a d i u s =7.951 km), with different values of parameter n ranging from 0.5 to 3.4. our suggested solution is free from physical and geometric singularities, satisfies causality condition, abreu's criterion and relativistic adiabatic index γ , and exhibits well-behaved nature, as well as, all energy conditions and equilibrium condition are well-defined, which implies that our model is physically acceptable. the physical sensitivity of the moment of inertia (i) obtained from the solutions is confirmed by the bejger-haensel concept, which could provide a precise tool to the matching rigidity of the state equation due to different values of n viz., n =0.5 ,1.08 ,1.66 ,2.24 ,2.82 and 3.4. | anisotropic relativistic fluid spheres: an embedding class i approach |
the variety of star formation histories (sfhs) of z ≳ 6 galaxies provides important insights into early star formation, but has been difficult to systematically quantify. some observations suggest that many z ~ 6-9 galaxies are dominated by ≳200 myr stellar populations, implying significant star formation at z ≳ 9, while others find that most reionization era galaxies are ≲10 myr, consistent with little z ≳ 9 star formation. here, we quantify the distribution of ages of uv-bright ($-22.5\lesssim m_{\rm \small uv}\lesssim -21$) galaxies colour-selected to lie at z ≃ 6.6-6.9, an ideal redshift range to systematically study the sfhs of reionization era galaxies with ground-based observatories and spitzer. we infer galaxy properties with two sed modelling codes and compare results, finding that stellar masses are largely insensitive to the model, but the inferred ages can vary by an order of magnitude. we infer a distribution of ages assuming a simple, parametric sfh model, finding a median age of ~30-70 myr depending on sed model. we quantify the fractions of ≤10 and ≥250 myr galaxies, finding that these systems comprise ~15-30 per cent and ~20-25 per cent of the population, respectively. with a flexible sfh model, the shapes of the sfhs are consistent with those implied by the simple model (e.g. young galaxies have rapidly rising sfhs). however, stellar masses can differ significantly, with those of young systems sometimes being more than an order of magnitude larger with the flexible sfh. we quantify the implications of these results for z ≳ 9 stellar mass assembly and discuss improvements expected from jwst. | star formation histories of uv-luminous galaxies at z ≃ 6.8: implications for stellar mass assembly at early cosmic times |
we present the vimos ultra deep survey (vuds), a spectroscopic redshift survey of ~10 000 very faint galaxies to study the main phase of galaxy assembly in 2 < z ≃ 6. the survey covers 1 deg2 in three separate fields: cosmos, ecdfs, and vvds-02h, with the selection of targets based on an inclusive combination of photometric redshifts and colour properties. spectra covering 3650 < λ < 9350 å are obtained with vimos on the eso-vlt with integration times of 14h. here we present the survey strategy, target selection, data processing, and the redshift measurement process with an emphasis on the specific methods used to adapt to this high-redshift range. we discuss the spectra quality and redshift reliability and derive a success rate in redshift measurement of 91%, or 74% by limiting the dataset to the most reliable measurements, down to a limiting magnitude iab = 25. measurements are performed all the way down to iab = 27. the mean redshift of the main sample is z ~ 3 and extends over a broad redshift range mainly in 2 < z < 6. at 3 < z < 5, the galaxies cover a wide range of luminosities -23 < mnuv < -20.5, stellar mass 109m⊙ < m∗ < 1011m⊙, and star formation rates 1m⊙/yr < sfr < 103m⊙/yr. we discuss the spectral properties of galaxies using individual as well asstacked spectra. the comparison between spectroscopic and photometric redshifts as well as colour selection demonstrate the effectiveness of our selection scheme. from about ~ 90% of the data analysed so far, we expect to assemble >6000 galaxies with reliable spectroscopic redshifts in 2 < z < 6 when complete. this makes the vuds the largest survey at these redshifts and offers the opportunity for unprecedented studies of the star-forming galaxy population and its distribution in large-scale structures during the main phase of galaxy assembly. based on data obtained with the european southern observatory very large telescope, paranal, chile, under large program 185.a-0791.staged releases of the data will appear on http://cesam.lam.fr/vuds/, starting in mid-2015. | the vimos ultra-deep survey: ~10 000 galaxies with spectroscopic redshifts to study galaxy assembly at early epochs 2 < z ≃ 6 |
we present the deep synoptic array (dsa-110) discovery and interferometric localization of the so far non-repeating frb 20220319d. the frb originates in a young, rapidly star-forming barred spiral galaxy, iras 02044$+$7048, at just 50 mpc. although the ne2001 and ymw16 models for the galactic interstellar-medium (ism) contribution to the dm of frb 20220319d exceed its total observed dm, we show that uncertainties in these models accommodate an extragalactic origin for the burst. we derive a conservative upper limit on the dm contributed by the circumgalactic medium (cgm) of the milky way: the limit is either 28.7 pc cm$^{-3}$ and 47.3 pc cm$^{-3}$, depending on which of two pulsars nearby on the sky to frb 20220319d is used to estimate the ism dm. these limits both imply that the total galactic cgm mass is $<10^{11}m_{\odot}$, and that the baryonic mass of the milky way is $\lesssim60\%$ of the cosmological average given the total halo mass. more stringent albeit less conservative constraints are possible when the dms of pulsars in the distant globular cluster m53 are additionally considered. although our constraints are sensitive to possible anisotropy in the cgm and to the assumed form of the radial-density profile, they are not subject to uncertainties in the chemical and thermal properties of the cgm. our results strongly support scenarios commonly predicted by galaxy-formation simulations wherein feedback processes expel baryonic matter from the halos of galaxies like the milky way. | deep synoptic array science: a 50 mpc fast radio burst constrains the mass of the milky way circumgalactic medium |
in recent years, the combination of precise quantum monte carlo (qmc) methods with realistic nuclear interactions and consistent electroweak currents, in particular those constructed within effective field theories (efts), has led to new insights in light and medium-mass nuclei, neutron matter, and electroweak reactions. for example, with the same chiral interactions, qmc calculations can reproduce binding energies and radii for light nuclei, n-α scattering phase shifts, and the neutron matter equation of state. this compelling new body of work has been made possible both by advances in qmc methods for nuclear physics, which push the bounds of applicability to heavier nuclei and to asymmetric nuclear matter, and by the development of local chiral eft interactions up to next-to-next-to-leading order and minimally nonlocal interactions including δ degrees of freedom. in this review, we discuss these recent developments and give an overview of the exciting results for nuclei, neutron matter and neutron stars, and electroweak reactions. | quantum monte carlo methods in nuclear physics: recent advances |
we present an analysis of seven strongly gravitationally lensed quasars and the corresponding constraints on the properties of dark matter. our results are derived by modelling the lensed image positions and flux-ratios using a combination of smooth macro-models and a population of low-mass haloes within the mass range of 106-109 m⊙. our lens models explicitly include higher order complexity in the form of stellar discs and luminous satellites, as well as low-mass haloes located along the observed lines of sight for the first time. assuming a cold dark matter (cdm) cosmology, we infer an average total mass fraction in substructure of $f_{\rm sub} = 0.012^{+0.007}_{-0.004}$ (68 per cent confidence limits), which is in agreement with the predictions from cdm hydrodynamical simulations to within 1σ. this result is closer to the predictions than those from previous studies that did not include line-of-sight haloes. under the assumption of a thermal relic dark matter model, we derive a lower limit on the particle relic mass of mth > 5.58 kev (95 per cent confidence limits), which is consistent with a value of mth > 5.3 kev from the recent analysis of the ly α forest. we also identify two main sources of possible systematic errors and conclude that deeper investigations in the complex structure of lens galaxies as well as the size of the background sources should be a priority for this field. | sharp - vii. new constraints on the dark matter free-streaming properties and substructure abundance from gravitationally lensed quasars |
context. water is a key molecule in the physics and chemistry of star and planet formation, but it is difficult to observe from earth. the herschel space observatory provided unprecedented sensitivity as well as spatial and spectral resolution to study water. the water in star-forming regions with herschel (wish) key program was designed to observe water in a wide range of environments and provide a legacy data set to address its physics and chemistry.aims: the aim of wish is to determine which physical components are traced by the gas-phase water lines observed with herschel and to quantify the excitation conditions and water abundances in each of these components. this then provides insight into how and where the bulk of the water is formed in space and how it is transported from clouds to disks, and ultimately comets and planets.methods: data and results from wish are summarized together with those from related open time programs. wish targeted ~80 sources along the two axes of luminosity and evolutionary stage: from low- to high-mass protostars (luminosities from <1 to > 105 l⊙) and from pre-stellar cores to protoplanetary disks. lines of h2o and its isotopologs, hdo, oh, co, and [o i], were observed with the hifi and pacs instruments, complemented by other chemically-related molecules that are probes of ultraviolet, x-ray, or grain chemistry. the analysis consists of coupling the physical structure of the sources with simple chemical networks and using non-lte radiative transfer calculations to directly compare models and observations.results: most of the far-infrared water emission observed with herschel in star-forming regions originates from warm outflowing and shocked gas at a high density and temperature (> 105 cm−3, 300-1000 k, v ~ 25 km s−1), heated by kinetic energy dissipation. this gas is not probed by single-dish low-j co lines, but only by co lines with jup > 14. the emission is compact, with at least two different types of velocity components seen. water is a significant, but not dominant, coolant of warm gas in the earliest protostellar stages. the warm gas water abundance is universally low: orders of magnitude below the h2o/h2 abundance of 4 × 10−4 expected if all volatile oxygen is locked in water. in cold pre-stellar cores and outer protostellar envelopes, the water abundance structure is uniquely probed on scales much smaller than the beam through velocity-resolved line profiles. the inferred gaseous water abundance decreases with depth into the cloud with an enhanced layer at the edge due to photodesorption of water ice. all of these conclusions hold irrespective of protostellar luminosity. for low-mass protostars, a constant gaseous hdo/h2o ratio of ~0.025 with position into the cold envelope is found. this value is representative of the outermost photodesorbed ice layers and cold gas-phase chemistry, and much higher than that of bulk ice. in contrast, the gas-phase nh3 abundance stays constant as a function of position in low-mass pre- and protostellar cores. water abundances in the inner hot cores are high, but with variations from 5 × 10−6 to a few × 10−4 for low- and high-mass sources. water vapor emission from both young and mature disks is weak.conclusions: the main chemical pathways of water at each of the star-formation stages have been identified and quantified. low warm water abundances can be explained with shock models that include uv radiation to dissociate water and modify the shock structure. uv fields up to 102−103 times the general interstellar radiation field are inferred in the outflow cavity walls on scales of the herschel beam from various hydrides. both high temperature chemistry and ice sputtering contribute to the gaseous water abundance at low velocities, with only gas-phase (re-)formation producing water at high velocities. combined analyses of water gas and ice show that up to 50% of the oxygen budget may be missing. in cold clouds, an elegant solution is that this apparently missing oxygen is locked up in larger μm-sized grains that do not contribute to infrared ice absorption. the fact that even warm outflows and hot cores do not show h2o at full oxygen abundance points to an unidentified refractory component, which is also found in diffuse clouds. the weak water vapor emission from disks indicates that water ice is locked up in larger pebbles early on in the embedded class i stage and that these pebbles have settled and drifted inward by the class ii stage. water is transported from clouds to disks mostly as ice, with no evidence for strong accretion shocks. even at abundances that are somewhat lower than expected, many oceans of water are likely present in planet-forming regions. based on the lessons for galactic protostars, the low-j h2o line emission (eup < 300 k) observed in extragalactic sources is inferred to be predominantly collisionally excited and to originate mostly from compact regions of current star formation activity. recommendations for future mid- to far-infrared missions are made. | water in star-forming regions: physics and chemistry from clouds to disks as probed by herschel spectroscopy |
we present a recalibration of the photometric systems in the pantheon+ sample of type ia supernovae (sne ia) including those in the sh0es distance-ladder measurement of h 0. we utilize the large and uniform sky coverage of the public pan-starrs stellar photometry catalog to cross calibrate against tertiary standards released by individual sn ia surveys. the most significant updates over the "supercal" cross calibration used for the previous pantheon and sh0es analyses are: (1) expansion of the number of photometric systems (now 25) and filters (now 105), (2) solving for all filter offsets in all systems simultaneously to produce a calibration uncertainty covariance matrix for cosmological-model constraints, and (3) accounting for the change in the fundamental flux calibration of the hubble space telescope calspec standards from previous versions on the order of 1.5% over a δλ of 4000 å. we retrain the salt2 model and find that our new model coupled with the new calibration of the light curves themselves causes a net distance modulus change (d μ/dz) of 0.04 mag over the redshift range 0 < z < 1. we introduce a new formalism to determine the systematic impact on cosmological inference by propagating the covariance in the fitted calibration offsets through retraining simultaneously with light-curve fitting and find a total calibration uncertainty impact of σw= 0.013; roughly half the size of the sample statistical uncertainty. similarly, we find the systematic sn calibration contribution to the sh0es h 0 uncertainty is less than 0.2 km s-1 mpc-1, suggesting that sn ia calibration cannot resolve the current level of the "hubble tension." | the pantheon+ analysis: supercal-fragilistic cross calibration, retrained salt2 light-curve model, and calibration systematic uncertainty |
we present results from the cosmic evolution early release survey on the stellar population parameters for 28 galaxies with redshifts 4 < z < 9 using imaging data from the james webb space telescope (jwst) mid-infrared instrument (miri) combined with data from the hubble space telescope and the spitzer space telescope. the jwst/miri 5.6 and 7.7 μm data extend the coverage of the rest-frame spectral energy distribution to nearly 1 μm for galaxies in this redshift range. by modeling the galaxies' seds the miri data show that the galaxies have, on average, rest-frame uv (1600 å)-i-band colors 0.4 mag bluer than derived when using photometry that lacks miri. therefore, the galaxies have lower ratios of stellar mass to light. the miri data reduce the stellar masses by $\langle {\rm{\delta }}\mathrm{log}{m}_{* }\rangle =0.25$ dex at 4 < z < 6 and 0.37 dex at 6 < z < 9. this also reduces the star formation rates (sfrs) by <δlogsfr> = 0.14 dex at 4 < z < 6 and 0.27 dex at 6 < z < 9. the miri data also improve constraints on the allowable stellar mass formed in early star formation. we model this using a star formation history that includes both a "burst" at zf= 100 and a slowly varying ("delayed-τ") model. the miri data reduce the allowable stellar mass by 0.6 dex at 4 < z < 6 and by ≈1 dex at 6 < z < 9. applying these results globally, this reduces the cosmic stellar-mass density by an order of magnitude in the early universe (z ≈ 9). therefore, observations of rest-frame ≳1 μm are paramount for constraining the stellar-mass buildup in galaxies at very high redshifts. | ceers key paper. v. galaxies at 4 < z < 9 are bluer than they appear-characterizing galaxy stellar populations from rest-frame1 μm imaging |
context. the improvements in the precision of the published data in gaia edr3 with respect to gaia dr2, particularly for parallaxes and proper motions, offer the opportunity to increase the number of known open clusters in the milky way by detecting farther and fainter objects that have thus far gone unnoticed.aims: our aim is to continue to complete the open cluster census in the milky way with the detection of new stellar groups in the galactic disc. we use gaia edr3 up to magnitude g = 18 mag, increasing the magnitude limit and therefore the search volume explored in one unit with respect to our previous studies.methods: we used the ocfinder method to search for new open clusters in gaia edr3 using a big data environment. as a first step, ocfinder identified stellar statistical overdensities in five-dimensional astrometric space (position, parallax, and proper motions) using the dbscan clustering algorithm. then, these overdensities were classified into random statistical overdensities or real physical open clusters using a deep artificial neural network trained on well-characterised g, gbp - grp colour-magnitude diagrams.results: we report the discovery of 628 new open clusters within the galactic disc, with most of them being located beyond 1 kpc from the sun. from the estimation of ages, distances, and line-of-sight extinctions of these open clusters, we see that young clusters align following the galactic spiral arms while older ones are dispersed in the galactic disc. furthermore, we find that most open clusters are located at low galactic altitudes with the exception of a few groups older than 1 gyr.conclusions: we show the success of the ocfinder method leading to the discovery of a total of 1274 open clusters (joining the discoveries here with the previous ones based on gaia dr2), which represents almost 50% of the known population. our ability to perform big data searches on a large volume of the galactic disc, together with the higher precision in gaia edr3, enable us to keep completing the census with the discovery of new open clusters. full table 1 and table 2 are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/661/a118 | hunting for open clusters in gaia edr3: 628 new open clusters found with ocfinder |
the physical properties of fast radio burst (frb) host galaxies provide important clues towards the nature of frb sources. the 16 frb hosts identified thus far span three orders of magnitude in mass and specific star formation rate, implicating a ubiquitously occurring progenitor object. frbs localized with ~arcsecond accuracy also enable effective searches for associated multiwavelength and multi-time-scale counterparts, such as the persistent radio source associated with frb 20121102a. here we present a localization of the repeating source frb 20201124a, and its association with a host galaxy (sdss j050803.48+260338.0, z = 0.098) and persistent radio source. the galaxy is massive (${\sim}3\times 10^{10}\, \text{m}_{\odot }$), star-forming (few solar masses per year), and dusty. very large array and very long baseline array observations of the persistent radio source measure a luminosity of 1.2 × 1029 erg s-1 hz-1, and show that is extended on scales ≳50 mas. we associate this radio emission with the ongoing star formation activity in sdss j050803.48+260338.0. deeper, high-resolution optical observations are required to better utilize the milliarcsecond-scale localization of frb 20201124a and determine the origin of the large dispersion measure (150-220 pc cm-3) contributed by the host. sdss j050803.48+260338.0 is an order of magnitude more massive than any galaxy or stellar system previously associated with a repeating frb source, but is comparable to the hosts of so far non-repeating frbs, further building the link between the two apparent populations. | the host galaxy and persistent radio counterpart of frb 20201124a |
phoebe 2 is a python package for modeling the observables of eclipsing star systems, but until now it has focused entirely on the forward model—that is, generating a synthetic model given fixed values of a large number of parameters describing the system and the observations. the inverse problem, obtaining orbital and stellar parameters given observational data, is more complicated and computationally expensive as it requires generating a large set of forward models to determine which set of parameters and uncertainties best represents the available observational data. the process of determining the best solution and also of obtaining reliable and robust uncertainties on those parameters often requires the use of multiple algorithms, including both optimizers and samplers. furthermore, the forward model of phoebe has been designed to be as physically robust as possible, but it is computationally expensive compared to other codes. it is useful, therefore, to use whichever code is most efficient given the reasonable assumptions for a specific system, but learning the intricacies of multiple codes presents a barrier to doing this in practice. here we present release 2.3 of phoebe (publicly available from http://phoebe-project.org), which introduces a general framework for defining and handling distributions on parameters and utilizing multiple different estimation, optimization, and sampling algorithms. the presented framework supports multiple forward models, including the robust model built into phoebe itself. | physics of eclipsing binaries. v. general framework for solving the inverse problem |
the fuzzy dark matter (fdm) model treats dm as a bosonic field with an astrophysically large de broglie wavelength. a striking feature of this model is o (1 ) fluctuations in the dark matter density on time scales which are shorter than the gravitational timescale. including, for the first time, the effect of core oscillations, we demonstrate how such fluctuations lead to heating of star clusters and, thus, an increase in their size over time. from the survival of the old star cluster in eridanus ii, we infer ma≳0.6 →1 ×10-19 ev within modeling uncertainty if fdm is to compose all of the dm and derive constraints on the fdm fraction at lower masses. the subhalo mass function in the milky way implies ma≳0.8 ×10-21 ev to successfully form eridanus ii. the region between 10-21 and 10-20 ev is affected by narrow band resonances. however, the limited applicability of the diffusion approximation means that some of this region may still be consistent with observations of eridanus ii. | strong constraints on fuzzy dark matter from ultrafaint dwarf galaxy eridanus ii |
context. the relevance of m dwarfs in the search for potentially habitable earth-sized planets has grown significantly in the last years.aims: in our on-going effort to comprehensively and accurately characterise confirmed and potential planet-hosting m dwarfs, in particular for the carmenes survey, we have carried out a comprehensive multi-band photometric analysis involving spectral energy distributions, luminosities, absolute magnitudes, colours, and spectral types, from which we have derived basic astrophysical parameters.methods: we have carefully compiled photometry in 20 passbands from the ultraviolet to the mid-infrared, and combined it with the latest parallactic distances and close-multiplicity information, mostly from gaia dr2, of a sample of 2479 k5 v to l8 stars and ultracool dwarfs, including 2210 nearby, bright m dwarfs. for this, we made extensive use of virtual observatory tools.results: we have homogeneously computed accurate bolometric luminosities and effective temperatures of 1843 single stars, derived their radii and masses, studied the impact of metallicity, and compared our results with the literature. the over 40 000 individually inspected magnitudes, together with the basic data and derived parameters of the stars, individual and averaged by spectral type, have been made public to the astronomical community. in addition, we have reported 40 new close multiple systems and candidates (ρ < 3.3 arcsec) and 36 overluminous stars that are assigned to young galactic populations.conclusions: in the new era of exoplanet searches around m dwarfs via transit (e.g. tess, plato) and radial velocity (e.g. carmenes, nirps+harps), this work is of fundamental importance for stellar and therefore planetary parameter determination. table a.3 is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/642/a115 | carmenes input catalogue of m dwarfs. v. luminosities, colours, and spectral energy distributions |
we characterize the occurrence rate of planets, ranging in size from 0.5 to 16 r ⊕, orbiting fgk stars with orbital periods from 0.5 to 500 days. our analysis is based on results from the “dr25” catalog of planet candidates produced by nasa’s kepler mission and stellar radii from gaia “dr2.” we incorporate additional kepler data products to accurately characterize the efficiency of planets being recognized as “threshold crossing events” by kepler’s transiting planet search pipeline and labeled as planet candidates by the robovetter. using a hierarchical bayesian model, we derive planet occurrence rates for a wide range of planet sizes and orbital periods. for planets with sizes 0.75-1.5 r ⊕ and orbital periods of 237-500 days, we find a rate of planets per fgk star of <0.27 (84.13th percentile). while the true rate of such planets could be lower by a factor of ∼2 (primarily due to potential contamination of planet candidates by false alarms), the upper limits on the occurrence rate of such planets are robust to ∼10%. we recommend that mission concepts aiming to characterize potentially rocky planets in or near the habitable zone of sun-like stars prepare compelling science programs that would be robust for a true rate in the range fr,p= 0.03-0.40 for 0.75-1.5 r ⊕ planets with orbital periods in 237-500 days, or a differential rate of {{{γ }}}\oplus \equiv ({d}2f)/[d({ln}p) d({ln}{r}p)]= 0.06-0.76. | occurrence rates of planets orbiting fgk stars: combining kepler dr25, gaia dr2, and bayesian inference |
studies of the ages, abundances, and motions of individual stars in the milky way provide one of the best ways to study the evolution of disc galaxies over cosmic time. the formation of the milky way's barred inner region in particular is a crucial piece of the puzzle of disc galaxy evolution. using data from apogee and gaia, we present maps of the kinematics, elemental abundances, and age of the milky way bulge and disc that show the barred structure of the inner milky way in unprecedented detail. the kinematic maps allow a direct, purely kinematic determination of the bar's pattern speed of 41± 3 km s^{-1} kpc^{-1} and of its shape and radial profile. we find the bar's age, metallicity, and abundance ratios to be the same as those of the oldest stars in the disc that are formed in its turbulent beginnings, while stars in the bulge outside of the bar are younger and more metal-rich. this implies that the bar likely formed {≈}8 gyr ago, when the decrease in turbulence in the gas disc allowed a thin disc to form that quickly became bar-unstable. the bar's formation therefore stands as a crucial epoch in the evolution of the milky way, a picture that is in line with the evolutionary path that emerges from observations of the gas kinematics in external disc galaxies over the last {≈}10 gyr. | life in the fast lane: a direct view of the dynamics, formation, and evolution of the milky way's bar |
in this review we present a progress report of the connection between long-duration gamma-ray bursts (grbs) and their accompanying supernovae (sne). the analysis is from the point of view of an observer, with much of the emphasis placed on how observations, and the modelling of observations, have constrained what we known about grb-sne. we discuss their photometric and spectroscopic properties, their role as cosmological probes, including their measured luminosity$-$decline relationships, and how they can be used to measure the hubble constant. we present a statistical analysis of their bolometric properties, and use this to determine the properties of the "average" grb-sne: which has a kinetic energy of $e_{\rm k} \approx 2.5\times10^{52}$ erg, an ejecta mass of $m_{\rm ej} \approx 6$ m$_{\odot}$, a nickel mass of $m_{\rm ni} \approx 0.4$ m$_{\odot}$, a peak photospheric velocity of $v_{\rm ph} \approx 21,000$ km s$^{-1}$, a peak bolometric luminosity of $l_{\rm p} \approx 1\times10^{43}$ erg s$^{-1}$, and it reaches peak bolometric light in $t_{\rm p} \approx 13$ days. we discuss their geometry, consider the various physical processes that are thought to power the luminosity of grb-sne, and whether differences exist between grb-sne and the sne associated with ultra-long duration grbs. we discuss how observations of the environments of grb-sne further constrain the physical properties of their progenitor stars, and give an overview of the current theoretical paradigms of their suspected central engines. we also present an overview of the radioactively powered transients that have been photometrically associated with short-duration grbs. we conclude the review by discussing what additional research is needed to further our understanding of grb-sne, in particular the role of binary-formation channels and the connection of grb-sne with superluminous sne (abridged). | the observer's guide to the gamma-ray burst supernova connection |
recent spatially-resolved observations of protoplanetary disks revealed a plethora of substructures, including concentric rings and gaps, inner cavities, misalignments, spiral arms, and azimuthal asymmetries. this is the major breakthrough in studies of protoplanetary disks since protostars and planets vi (ppvi) and is reshaping the field of planet formation. however, while the capability of imaging substructures in protoplanetary disks has been steadily improving, the origin of many substructures are still largely debated. the structured distributions of gas and solids in protoplanetary disks likely reflect the outcome of physical processes at work, including the formation of planets. yet, the diverse properties among the observed protoplanetary disk population, for example, the number and radial location of rings and gaps in the dust distribution, suggest that the controlling process may differ between disks and/or the outcome may be sensitive to stellar or disk properties. in this review, we (1) summarize the existing observations of protoplanetary disk substructures collected from the literature; (2) provide a comprehensive theoretical review of various processes proposed to explain observed protoplanetary disk substructures; (3) compare current theoretical predictions with existing observations and highlight future research directions to distinguish between different origins; and (4) discuss implications of state-of-the-art protoplanetary disk observations to protoplanetary disk and planet formation theory. | structured distributions of gas and solids in protoplanetary disks |
the rotation of a star and the revolutions of its planets are not necessarily aligned. this article reviews the measurement techniques, key findings, and theoretical interpretations related to the obliquities (spin-orbit angles) of planet-hosting stars. the best measurements are for stars with short-period giant planets, which have been found on prograde, polar, and retrograde orbits. it seems likely that dynamical processes such as planet-planet scattering and secular perturbations are responsible for tilting the orbits of close-in giant planets, just as those processes are implicated in exciting orbital eccentricities. the observed dependence of the obliquity on orbital separation, planet mass, and stellar structure suggests that in some cases, tidal dissipation damps a star's obliquity within its main-sequence lifetime. the situation is not as clear for stars with smaller or wider-orbiting planets. although the earliest measurements of such systems tended to find low obliquities, some glaring exceptions are now known in which the star's rotation is misaligned with respect to the coplanar orbits of multiple planets. in addition, statistical analyses based on projected rotation velocities and photometric variability have found a broad range of obliquities for f-type stars hosting compact multiple-planet systems. the results suggest it is unsafe to assume that stars and their protoplanetary disks are aligned. primordial misalignments might be produced by neighboring stars or more complex events that occur during the epoch of planet formation. | stellar obliquities in exoplanetary systems |
about ten per cent of `massive' stars (those of more than 1.5 solar masses) have strong, large-scale surface magnetic fields1-3. it has been suggested that merging of main-sequence and pre-main-sequence stars could produce such strong fields4,5, and the predicted fraction of merged massive stars is also about ten per cent6,7. the merger hypothesis is further supported by a lack of magnetic stars in close binaries8,9, which is as expected if mergers produce magnetic stars. here we report three-dimensional magnetohydrodynamical simulations of the coalescence of two massive stars and follow the evolution of the merged product. strong magnetic fields are produced in the simulations, and the merged star rejuvenates such that it appears younger and bluer than other coeval stars. this can explain the properties of the magnetic `blue straggler' star τ sco in the upper scorpius association that has an observationally inferred, apparent age of less than five million years, which is less than half the age of its birth association10. such massive blue straggler stars seem likely to be progenitors of magnetars, perhaps giving rise to some of the enigmatic fast radio bursts observed11, and their supernovae may be affected by their strong magnetic fields12. | stellar mergers as the origin of magnetic massive stars |
sdss-iv manga (mapping nearby galaxies at apache point observatory) is the largest integral-field unit (ifu) spectroscopy survey to date, aiming to observe a statistically representative sample of 10,000 low-redshift galaxies. in this paper, we study the reliability of the emission-line fluxes and kinematic properties derived by the manga data analysis pipeline (dap). we describe the algorithmic choices made in the dap with regards to measuring emission-line properties, and the effect of our adopted strategy of simultaneously fitting the continuum and line emission. the effects of random errors are quantified by studying various fit-quality metrics, idealized recovery simulations, and repeat observations. this analysis demonstrates that the emission lines are well fit in the vast majority of the manga data set and the derived fluxes and errors are statistically robust. the systematic uncertainty on emission-line properties introduced by the choice of continuum templates is also discussed. in particular, we test the effect of using different stellar libraries and simple stellar-population models on the derived emission-line fluxes and the effect of introducing different tying prescriptions for the emission-line kinematics. we show that these effects can generate large (>0.2 dex) discrepancies at low signal-to-noise ratio and for lines with low equivalent width (ew); however, the combined effect is noticeable even for hα ew > 6 å. we provide suggestions for optimal use of the data provided by sdss data release 15 and propose refinements on the dap for future manga data releases. | the data analysis pipeline for the sdss-iv manga ifu galaxy survey: emission-line modeling |
gamma-ray bursts (grbs), which are bright flashes of gamma rays from extragalactic sources followed by fading afterglow emission, are associated with stellar core collapse events. we report the detection of very-high-energy (vhe) gamma rays from the afterglow of grb 190829a, between 4 and 56 hours after the trigger, using the high energy stereoscopic system (h.e.s.s.). the low luminosity and redshift of grb 190829a reduce both internal and external absorption, allowing determination of its intrinsic energy spectrum. between energies of 0.18 and 3.3 tera-electron volts, this spectrum is described by a power law with photon index of 2.07 ± 0.09, similar to the x-ray spectrum. the x-ray and vhe gamma-ray light curves also show similar decay profiles. these similar characteristics in the x-ray and gamma-ray bands challenge grb afterglow emission scenarios. | revealing x-ray and gamma ray temporal and spectral similarities in the grb 190829a afterglow |
the main sequence (ms) of star-forming (sf) galaxies plays a fundamental role in driving galaxy evolution and our efforts to understand it. however, different studies find significant differences in the normalization, slope, and shape of the ms. these discrepancies arise mainly from the different selection criteria adopted to isolate sf galaxies, which may include or exclude galaxies with a specific star formation rate (sfr) substantially below the ms value. to obviate this limitation of all current criteria, we propose an objective definition of the ms that does not rely at all on a pre-selection of sf galaxies. constructing the 3d sfr-mass-number plot, the ms is then defined as the ridge line of the sf peak, as illustrated with various figures. the advantages of such a definition are manifold. if generally adopted, it will facilitate the inter-comparison of results from different groups using the same sfr and stellar mass diagnostics, or it will highlight the relative systematics of different diagnostics. all of this could help to understand ms galaxies as systems in a quasi-steady state equilibrium and would also provide a more objective criterion for identifying quenching galaxies. | an objective definition for the main sequence of star-forming galaxies |
lynx is the next-generation observatory which will provide unprecedented x-ray vision into the otherwise invisible universe to gain understanding of origins and physics of the cosmos. lynx will see the dawn of black holes, reveal what drives galaxy formation and evolution, and unveil the energetic side of stellar evolution and stellar ecosystems. lynx science payload will enables radical advances and leaps in capability over nasa's existing flagship chandra and the esa's planned athena mission: 100-fold increase in sensitivity via coupling superb angular resolution with high throughput; 16 times larger field of view (fov) for sub-arcsecond imaging; and 10-20 times higher spectral resolution for both point-like and extended sources. the lynx design reference mission has been designed to meet the science objectives of the future while capitalizing where appropriate on decades of experience, and especially from efficient, flight-proven approaches, design choices, and mission operations software and procedures developed for chandra. while the science program outlined for lynx in this report is already very broad, the observatory is designed such that there will be ample resources to execute many other programs, even those not anticipated today. virtually all astronomers will be able to use lynx for their own particular science. | the lynx mission concept study interim report |
kinetic plasma turbulence cascade spans multiple scales ranging from macroscopic fluid flow to sub-electron scales. mechanisms that dissipate large scale energy, terminate the inertial range cascade, and convert kinetic energy into heat are hotly debated. here, we revisit these puzzles using fully kinetic simulation. by performing scale-dependent spatial filtering on the vlasov equation, we extract information at prescribed scales and introduce several energy transfer functions. this approach allows highly inhomogeneous energy cascade to be quantified as it proceeds down to kinetic scales. the pressure work, - ( p . ∇ ) . u , can trigger a channel of the energy conversion between fluid flow and random motions, which contains a collision-free generalization of the viscous dissipation in collisional fluid. both the energy transfer and the pressure work are strongly correlated with velocity gradients. | energy transfer, pressure tensor, and heating of kinetic plasma |
we present a high-resolution (∼0.″12, ∼16 au, mean sensitivity of 50 μjy beam-1 at 225 ghz) snapshot survey of 32 protoplanetary disks around young stars with spectral type earlier than m3 in the taurus star-forming region using the atacama large millimeter array. this sample includes most mid-infrared excess members that were not previously imaged at high spatial resolution, excluding close binaries and objects with high extinction, thereby providing a more representative look at disk properties at 1-2 myr. our 1.3 mm continuum maps reveal 12 disks with prominent dust gaps and rings, 2 of which are around primary stars in wide binaries, and 20 disks with no resolved features at the observed resolution (hereafter smooth disks), 8 of which are around the primary star in wide binaries. the smooth disks were classified based on their lack of resolved substructures, but their most prominent property is that they are all compact with small effective emission radii (r eff,95% ≲ 50 au). in contrast, all disks with r eff,95% of at least 55 au in our sample show detectable substructures. nevertheless, their inner emission cores (inside the resolved gaps) have similar peak brightness, power-law profiles, and transition radii to the compact smooth disks, so the primary difference between these two categories is the lack of outer substructures in the latter. these compact disks may lose their outer disk through fast radial drift without dust trapping, or they might be born with small sizes. the compact dust disks, as well as the inner disk cores of extended ring disks, that look smooth at the current resolution will likely show small-scale or low-contrast substructures at higher resolution. the correlation between disk size and disk luminosity correlation demonstrates that some of the compact disks are optically thick at millimeter wavelengths. | compact disks in a high-resolution alma survey of dust structures in the taurus molecular cloud |
we combine optical, near-infrared, and mid-infrared spectra and photometry to construct expanded spectral energy distributions for 145 field age (>500 myr) and 53 young (lower age estimate <500 myr) ultracool dwarfs (m6-t9). this range of spectral types includes very low mass stars, brown dwarfs, and planetary mass objects, providing fundamental parameters across both the hydrogen and deuterium burning minimum masses for the largest sample assembled to date. a subsample of 29 objects have well constrained ages as probable members of a nearby young moving group. we use 182 parallaxes and 16 kinematic distances to determine precise bolometric luminosities (lbol) and radius estimates from evolutionary models give semi-empirical effective temperatures (teff) for the full range of young and field age late-m, l, and t dwarfs. we construct age-sensitive relationships of luminosity, temperature, and absolute magnitude as functions of spectral type and absolute magnitude to disentangle the effects of degenerate physical parameters such as teff, surface gravity, and clouds on spectral morphology. we report bolometric corrections in j for both field age and young objects and find differences of up to a magnitude for late-l dwarfs. our correction in ks shows a larger dispersion but not necessarily a different relationship for young and field age sequences. we also characterize the nir-mir reddening of low gravity l dwarfs and identify a systematically cooler teff of up to 300 k from field age objects of the same spectral type and 400 k cooler from field age objects of the same mh magnitude. | fundamental parameters and spectral energy distributions of young and field age objects with masses spanning the stellar to planetary regime |
the javalambre-physics of the accelerating universe astrophysical survey (j-pas) will scan thousands of square degrees of the northern sky with a unique set of 56 filters using the dedicated 2.55 m javalambre survey telescope (jst) at the javalambre astrophysical observatory. prior to the installation of the main camera (4.2 deg2 field-of-view with 1.2 gpixels), the jst was equipped with the jpas-pathfinder, a one ccd camera with a 0.3 deg2 field-of-view and plate scale of 0.23 arcsec pixel−1. to demonstrate the scientific potential of j-pas, the jpas-pathfinder camera was used to perform minijpas, a ∼1 deg2 survey of the aegis field (along the extended groth strip). the field was observed with the 56 j-pas filters, which include 54 narrow band (fwhm ∼ 145 å) and two broader filters extending to the uv and the near-infrared, complemented by the u, g, r, i sdss broad band filters. in this minijpas survey overview paper, we present the minijpas data set (images and catalogs), as we highlight key aspects and applications of these unique spectro-photometric data and describe how to access the public data products. the data parameters reach depths of magab ≃ 22−23.5 in the 54 narrow band filters and up to 24 in the broader filters (5σ in a 3″ aperture). the minijpas primary catalog contains more than 64 000 sources detected in the r band and with matched photometry in all other bands. this catalog is 99% complete at r = 23.6 (r = 22.7) mag for point-like (extended) sources. we show that our photometric redshifts have an accuracy better than 1% for all sources up to r = 22.5, and a precision of ≤0.3% for a subset consisting of about half of the sample. on this basis, we outline several scientific applications of our data, including the study of spatially-resolved stellar populations of nearby galaxies, the analysis of the large scale structure up to z ∼ 0.9, and the detection of large numbers of clusters and groups. sub-percent redshift precision can also be reached for quasars, allowing for the study of the large-scale structure to be pushed to z > 2. the minijpas survey demonstrates the capability of the j-pas filter system to accurately characterize a broad variety of sources and paves the way for the upcoming arrival of j-pas, which will multiply this data by three orders of magnitude. minijpas data and associated value added catalogs are publicly available http://archive.cefca.es/catalogues/minijpas-pdr201912 | the minijpas survey: a preview of the universe in 56 colors |
kink oscillations of coronal loops, i.e., standing kink waves, is one of the most studied dynamic phenomena in the solar corona. the oscillations are excited by impulsive energy releases, such as low coronal eruptions. typical periods of the oscillations are from a few to several minutes, and are found to increase linearly with the increase in the major radius of the oscillating loops. it clearly demonstrates that kink oscillations are natural modes of the loops, and can be described as standing fast magnetoacoustic waves with the wavelength determined by the length of the loop. kink oscillations are observed in two different regimes. in the rapidly decaying regime, the apparent displacement amplitude reaches several minor radii of the loop. the damping time which is about several oscillation periods decreases with the increase in the oscillation amplitude, suggesting a nonlinear nature of the damping. in the decayless regime, the amplitudes are smaller than a minor radius, and the driver is still debated. the review summarises major findings obtained during the last decade, and covers both observational and theoretical results. observational results include creation and analysis of comprehensive catalogues of the oscillation events, and detection of kink oscillations with imaging and spectral instruments in the euv and microwave bands. theoretical results include various approaches to modelling in terms of the magnetohydrodynamic wave theory. properties of kink oscillations are found to depend on parameters of the oscillating loop, such as the magnetic twist, stratification, steady flows, temperature variations and so on, which make kink oscillations a natural probe of these parameters by the method of magnetohydrodynamic seismology. | kink oscillations of coronal loops |
we use data from the esa gaia mission early data release 3 (edr3) to measure the trigonometric parallax of ω cen, the first high-precision parallax measurement for the most massive globular cluster in the milky way. we use a combination of positional and high-quality proper motion data from edr3 to identify over 100,000 cluster members, of which 67,000 are in the magnitude and color range where edr3 parallaxes are best calibrated. we find the estimated parallax to be robust, demonstrating good control of systematics within the color-magnitude diagram of the cluster. we find a parallax for the cluster of 0.191 ± 0.001 (statistical) ±0.004 (systematic) mas (2.2% total uncertainty) corresponding to a distance of 5.24 ± 0.11 kpc. the parallax of ω cen provides a unique opportunity to directly and geometrically calibrate the luminosity of the tip of the red giant branch (trgb) because it is the only cluster with sufficient mass to provide enough red giant stars, more than 100 one magnitude below the tip, for a precise, model-free measurement of the tip. combined with the preexisting and most widely used measurements of the tip and foreground milky way extinction, we find mi,trgb =-3.97 ± 0.06 mag for the i-band luminosity of the blue edge. using the trgb luminosity calibrated from the gaia edr3 parallax of ω cen to calibrate the luminosity of type ia supernovae results in a value for the hubble constant of h0 = 72.1 ± 2.0 km s-1 mpc-1. we make the data for the stars in ω cen available electronically and encourage independent analyses of the results presented here. | the parallax of ω centauri measured from gaia edr3 and a direct, geometric calibration of the tip of the red giant branch and the hubble constant |
general relativity can be formulated equivalently with a non-riemannian geometry that associates with an affine connection of nonzero nonmetricity q but vanishing curvature r and torsion t . modification based on this description of gravity generates the f (q ) gravity. in this work, we explore the application of f (q ) gravity to the spherically symmetric configurations. we discuss the gauge fixing and connections in this setting. we demonstrate the effects of f (q ) by considering the external and internal solutions of compact stars. the external background solutions for any regular form of f (q ) coincide with the corresponding solutions in general relativity, i.e., the schwarzschild-de sitter solution and the reissner-nordström-de sitter solution with an electromagnetic field. for internal structure, with a simple model f (q )=q +α q2 and a polytropic equation of state, we find that a negative modification (α <0 ) provides support to more stellar masses while a positive one (α >0 ) reduces the amount of matter of the star. | spherically symmetric configuration in f (q ) gravity |
gravitational forces are expected to excite spiral density waves in protoplanetary disks, disks of gas and dust orbiting young stars. however, previous observations that showed spiral structure were not able to probe disk midplanes, where most of the mass is concentrated and where planet formation takes place. using the atacama large millimeter/submillimeter array, we detected a pair of trailing symmetric spiral arms in the protoplanetary disk surrounding the young star elias 2-27. the arms extend to the disk outer regions and can be traced down to the midplane. these millimeter-wave observations also reveal an emission gap closer to the star than the spiral arms. we argue that the observed spirals trace shocks of spiral density waves in the midplane of this young disk. | spiral density waves in a young protoplanetary disk |
the gravitational wave (gw) event gw170817 from a binary neutron star merger together with the electromagnetic counterpart showed that the speed of gws ct is very close to that of light for the redshift z < 0.009. this places tight constraints on dark energy models constructed in the framework of modified gravitational theories. we review models of the late-time cosmic acceleration in scalar-tensor theories with second-order equations of motion (dubbed horndeski theories) by paying particular attention to the evolution of dark energy equation of state and observables relevant to the cosmic growth history. we provide a gauge-ready formulation of scalar perturbations in full horndeski theories and estimate observables associated with the evolution of large-scale structures, cosmic microwave background and weak lensing by employing a so-called quasi-static approximation for the modes deep inside the sound horizon. in light of the recent observational bound of ct, we also classify surviving dark energy models into four classes depending on different structure-formation patterns and discuss how they can be observationally distinguished from each other. in particular, the nonminimally coupled theories in which the scalar field ϕ has a coupling with the ricci scalar r of the form g4(ϕ)r, including f(r) gravity, can be tightly constrained not only from the cosmic expansion and growth histories but also from the variation of screened gravitational couplings. the cross-correlation of integrated sachs-wolfe signal with galaxy distributions can be a key observable for placing bounds on the relative ratio of cubic galileon density to total dark energy density. the dawn of gw astronomy will open up a new window to constrain nonminimally coupled theories further by the modified luminosity distance of tensor perturbations. | dark energy in horndeski theories after gw170817: a review |
the properties of the first galaxies, expected to drive the cosmic dawn and the epoch of reionization, are encoded in the 3d structure of the cosmic 21-cm signal. parameter inference from upcoming 21-cm observations promises to revolutionize our understanding of these unseen galaxies. however, prior inference was done using models with several simplifying assumptions. here we introduce a flexible, physically motivated parametrization for high-z galaxy properties, implementing it in the public code 21cmfast. in particular, we allow their star formation rates and ionizing escape fraction to scale with the masses of their host dark matter haloes, and directly compute inhomogeneous, sub-grid recombinations in the intergalactic medium. combining current hubble observations of the rest-frame uv luminosity function (uv lf) at high-z with a mock 1000-h 21-cm observation using the hydrogen epoch of reionization arrays, we constrain the parameters of our model using a monte carlo markov chain sampler of 3d simulations, 21cmmc. we show that the amplitude and scaling of the stellar mass with halo mass are strongly constrained by lf observations, while the remaining galaxy properties are constrained mainly by 21-cm observations. the two data sets compliment each other quite well, mitigating degeneracies intrinsic to each observation. all eight of our astrophysical parameters are able to be constrained at the level of {∼ } 10{{ per cent}} or better. the updated versions of 21cmfast and 21cmmc used in this work are publicly available. | inferring the astrophysics of reionization and cosmic dawn from galaxy luminosity functions and the 21-cm signal |
tidal streams are highly sensitive to perturbations from passing dark matter (dm) subhalos and thus provide a means of measuring their abundance. in a recent paper, we analyzed the distribution of stars along the gd-1 stream with a combination of data from the gaia satellite and the pan-starrs survey, and we demonstrated that the population of dm subhalos predicted by the cold dark matter (cdm) paradigm are necessary and sufficient to explain the perturbations observed in the linear density of stars. in this paper, we use the measurements of the subhalo mass function (shmf) from the gd-1 data combined with a similar analysis of the pal 5 stream to provide novel constraints on alternative dm scenarios that predict a suppression of the shmf on scales smaller than the mass of dwarf galaxies, marginalizing over uncertainties in the slope and normalization of the unsuppressed shmf and the susceptibility of dm subhalos in the inner milky way to tidal disruption. in particular, we derive a 95% lower limit on the mass of warm dark matter (wdm) thermal relics mwdm > 3.6 kev from streams alone that strengthens to mwdm > 6.2 kev when adding dwarf satellite counts. similarly, we constrain the axion mass in ultra-light ("fuzzy") dark matter (fdm) models to be mfdm > 1.4 × 10-21 ev from streams alone or mfdm > 2.2 × 10-21 ev when adding dwarf satellite counts. because we make use of simple approximate forms of the streams' shmf measurement, our analysis is easy to replicate with other alternative dm models that lead to a suppression of the shmf. | novel constraints on the particle nature of dark matter from stellar streams |
we present panchromatic observations and modeling of supernova (sn) 2020tlf, the first normal type ii-p/l sn with confirmed precursor emission, as detected by the young supernova experiment transient survey. pre-sn activity was detected in riz-bands at -130 days and persisted at relatively constant flux until first light. soon after discovery, "flash" spectroscopy of sn 2020tlf revealed narrow, symmetric emission lines that resulted from the photoionization of circumstellar material (csm) shed in progenitor mass-loss episodes before explosion. surprisingly, this novel display of pre-sn emission and associated mass loss occurred in a red supergiant (rsg) progenitor with zero-age main-sequence mass of only 10-12 m ⊙, as inferred from nebular spectra. modeling of the light curve and multi-epoch spectra with the non-lte radiative-transfer code cmfgen and radiation-hydrodynamical code heracles suggests a dense csm limited to r ≈ 1015 cm, and mass-loss rate of 10-2 m ⊙ yr-1. the luminous light-curve plateau and persistent blue excess indicates an extended progenitor, compatible with an rsg model with r ⋆ = 1100 r ⊙. limits on the shock-powered x-ray and radio luminosity are consistent with model conclusions and suggest a csm density of ρ < 2 × 10-16 g cm-3 for distances from the progenitor star of r ≈ 5 × 1015 cm, as well as a mass-loss rate of $\dot{m}\lt 1.3\times {10}^{-5}\,{m}_{\odot }\,{\mathrm{yr}}^{-1}$ at larger distances. a promising power source for the observed precursor emission is the ejection of stellar material following energy disposition into the stellar envelope as a result of gravity waves emitted during either neon/oxygen burning or a nuclear flash from silicon combustion. | final moments. i. precursor emission, envelope inflation, and enhanced mass loss preceding the luminous type ii supernova 2020tlf |
we present a method to accelerate the evaluation of the likelihood in gravitational wave parameter estimation. parameter estimation codes compute likelihoods of similar waveforms, whose phases and amplitudes differ smoothly with frequency. we exploit this by precomputing frequency-binned overlaps of the best-fit waveform with the data. we show how these summary data can be used to approximate the likelihood of any waveform that is sufficiently probable within the required accuracy. we demonstrate that $\simeq 60$ bins suffice to accurately compute likelihoods for strain data at a sampling rate of $4096\,$hz and duration of $t=2048\,$s around the binary neutron star merger gw170817. relative binning speeds up parameter estimation for frequency domain waveform models by a factor of $\sim 10^4$ compared to naive matched filtering and $\sim 10$ compared to reduced order quadrature. | relative binning and fast likelihood evaluation for gravitational wave parameter estimation |
the detection of the binary neutron star merger gw170817 together with the observation of electromagnetic counterparts across the entire spectrum inaugurated a new era of multimessenger astronomy. in this study, we incorporate wavelength-dependent opacities and emissivities calculated from atomic-structure data enabling us to model both the measured light curves and spectra of the electromagnetic transient at2017gfo. best fits of the observational data are obtained by gaussian process regression, which allows us to present posterior samples for the kilonova and source properties connected to gw170817. incorporating constraints obtained from the gravitational wave signal measured by the ligo-virgo scientific collaboration, we present a 90 per cent upper bound on the mass ratio q ≲ 1.38 and a lower bound on the tidal deformability of ∼λ ≳ 197, which rules out sufficiently soft equations of state. our analysis is a path-finder for more realistic kilonova models and shows how the combination of gravitational wave and electromagnetic measurements allow for stringent constraints on the source parameters and the supranuclear equation of state. | constraints on the neutron star equation of state from at2017gfo using radiative transfer simulations |
we explore the ability of gravitational-wave detectors to extract the redshift distribution of binary black hole (bbh) mergers. the evolution of the merger rate across redshifts 0 < z ≲ 1 is directly tied to the formation and evolutionary processes, providing insight regarding the progenitor formation rate together with the distribution of time delays between formation and merger. because the limiting distance to which bbhs are detected depends on the masses of the binary, the redshift distribution of detected binaries depends on their underlying mass distribution. we therefore consider the mass and redshift distributions simultaneously, and fit the merger rate density, dn/dm 1 dm 2 dz. our constraints on the mass distribution agree with previously published results, including evidence for an upper mass cutoff at ∼40 m ⊙. additionally, we show that the current set of six bbh detections are consistent with a merger rate density that is uniform in comoving volume. although our constraints on the redshift distribution are not yet tight enough to distinguish between bbh formation channels, we show that it will be possible to distinguish between different astrophysically motivated models of the merger rate evolution with ∼100-300 laser interferometer gravitational-wave observatory/virgo detections (to be expected within 2-5 years). specifically, we will be able to infer whether the formation rate peaks at higher or lower redshifts than the star formation rate, or the typical time delay between formation and merger. meanwhile, with ∼100 detections, the inferred redshift distribution will place constraints on more exotic scenarios such as modified gravity. | does the black hole merger rate evolve with redshift? |
processes such as the scattering of alpha particles (4he), the triple-alpha reaction, and alpha capture play a major role in stellar nucleosynthesis. in particular, alpha capture on carbon determines the ratio of carbon to oxygen during helium burning, and affects subsequent carbon, neon, oxygen, and silicon burning stages. it also substantially affects models of thermonuclear type ia supernovae, owing to carbon detonation in accreting carbon-oxygen white-dwarf stars. in these reactions, the accurate calculation of the elastic scattering of alpha particles and alpha-like nuclei—nuclei with even and equal numbers of protons and neutrons—is important for understanding background and resonant scattering contributions. first-principles calculations of processes involving alpha particles and alpha-like nuclei have so far been impractical, owing to the exponential growth of the number of computational operations with the number of particles. here we describe an ab initio calculation of alpha-alpha scattering that uses lattice monte carlo simulations. we use lattice effective field theory to describe the low-energy interactions of protons and neutrons, and apply a technique called the ‘adiabatic projection method’ to reduce the eight-body system to a two-cluster system. we take advantage of the computational efficiency and the more favourable scaling with system size of auxiliary-field monte carlo simulations to compute an ab initio effective hamiltonian for the two clusters. we find promising agreement between lattice results and experimental phase shifts for s-wave and d-wave scattering. the approximately quadratic scaling of computational operations with particle number suggests that it should be possible to compute alpha scattering and capture on carbon and oxygen in the near future. the methods described here can be applied to ultracold atomic few-body systems as well as to hadronic systems using lattice quantum chromodynamics to describe the interactions of quarks and gluons. | ab initio alpha-alpha scattering |
faint lyα emitters become increasingly rarer toward the reionization epoch (z ∼ 6-7). however, observations from a very large (∼5 deg2) lyα narrow-band survey at z = 6.6 show that this is not the case for the most luminous emitters, capable of ionizing their own local bubbles. here we present follow-up observations of the two most luminous lyα candidates in the cosmos field: “masosa” and “cr7.” we used x-shooter, sinfoni, and fors2 on the very large telescope, and deimos on keck, to confirm both candidates beyond any doubt. we find redshifts of z = 6.541 and z = 6.604 for “masosa” and “cr7,” respectively. masosa has a strong detection in lyα with a line width of 386 ± 30 km s-1 (fwhm) and with very high ew0 (>200 å), but undetected in the continuum, implying very low stellar mass and a likely young, metal-poor stellar population. “cr7,” with an observed lyα luminosity of 1043.92±0.05 erg s-1 is the most luminous lyα emitter ever found at z > 6 and is spatially extended (∼16 kpc). “cr7” reveals a narrow lyα line with 266 ± 15 km s-1 fwhm, being detected in the near-infrared (nir) (rest-frame uv; β = -2.3 ± 0.1) and in irac/spitzer. we detect a narrow he ii 1640 å emission line (6σ, fwhm = 130 ± 30 km s-1) in cr7 which can explain the clear excess seen in the j-band photometry (ew0 ∼ 80 å). we find no other emission lines from the uv to the nir in our x-shooter spectra (he ii/o iii] 1663 å > 3 and he ii/c iii] 1908 å > 2.5). we conclude that cr7 is best explained by a combination of a popiii-like population, which dominates the rest-frame uv and the nebular emission, and a more normal stellar population, which presumably dominates the mass. hubble space telescope/wfc3 observations show that the light is indeed spatially separated between a very blue component, coincident with lyα and he ii emission, and two red components (∼5 kpc away), which dominate the mass. our findings are consistent with theoretical predictions of a popiii wave, with popiii star formation migrating away from the original sites of star formation. based on observations obtained with x-shooter, fors2, and sinfoni on the vlt, eso ddt time (294.a-5018, 294.a-5039) and with deimos on keck ii (u082d). | evidence for popiii-like stellar populations in the most luminous lyman-α emitters at the epoch of reionization: spectroscopic confirmation |
we calculate the properties of isospin-asymmetric nuclear matter based on chiral nucleon-nucleon (nn) and three-nucleon (3n) interactions. to this end, we develop an improved normal-ordering framework that allows us to include general 3n interactions starting from a plane-wave partial-wave-decomposed form. we present results for the energy per particle for general isospin asymmetries based on a set of different hamiltonians, study their saturation properties, the incompressibility, symmetry energy, and also provide an analytic parametrization for the energy per particle as a function of density and isospin asymmetry. | asymmetric nuclear matter based on chiral two- and three-nucleon interactions |
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