text:   Blue Compact Dwarf Galaxy",11,"['New paper out today on an unusually long lived transient in the tiny blue compact dwarf galaxy galaxy PHL 293B (<LINK>). This paper was led by Colin Burke, a grad student at UIUC. This mysterious source was lots fun to work on!', 'PHL 293B weighs a few tens of millions of solar masses and is extremely metal poor (~1/10th of solar metallicity). The image below is from the Legacy Survey (https://t.co/sVOtCBrAqw). https://t.co/vEJ1ZoHJH5', 'PHL 293B was found to have broad emission lines with blue-shifted absorption (800 km/s) in its SDSS spectroscopy in 2000. The broad emission was persistent for at least 10 years, and the source of the broad lines has been the topic of a lot of back and forth in the literature.', 'Broad lines, blue shifted absorption, but no strong optical variability or outbursts. Active galactic nucleus? Luminous blue variable? Stellar wind? Nothing seemed to quite fit the observational properties of PHL 293B.', 'In my 2018 paper searching for active galactic nuclei in Stripe 82 through optical photometric variability, I found this object to have very low-level variability. PHL 293B also turned up as variable in a similar search being done by Colin using the Dark Energy Survey.', 'We joined forces, and in our combined 20 year light curve, we see a very slow fading. This was a newly discovered feature of PHL 293B! https://t.co/lt5DrbrV8T', 'We decided to investigate further, and obtained new optical spectroscopy with Gemini in December 2019. This revealed that the broad H-alpha emission had finally faded! https://t.co/fJ4IxiQoa1', 'Between the (1) broad H-alpha emission lasting over a decade (2) recent disappearance of the broad lines (3) blue shifted absorption lines and (4) low-level photometric variability indicating a slow fade, we think that PHL 293B hosted an extremely long lived Type IIn supernova.', ""Broad lines from supernovae don't usually stick around for a decade+, but there are some indications that these extremely long lived transients are more common in these metal poor, gas-rich environments."", 'This really demonstrates the power of decades long light curves and multi-epoch spectroscopy! You can read lots more about the various scenarios we explored for PHL 293B here:  https://t.co/fSVnxcEdGp', ""Special thank you to @GeminiObs for granting us Director's Discretionary time! This work also uses repeat imaging data from @sdssurveys and @theDESurvey.""]",20,02,2305