ASASSN-19bt was a tidal disruption event (TDE) known for being the first such event discovered. It was discovered by the All Sky Automated Survey for SuperNovae (ASAS-SN) project, with early-time, detailed observations by the TESS satellite. It was first detected on January 21, 2019, and reached peak brightness on March 4. The black hole which caused the TDE has a mass of around 6 million suns and is in the 16th magnitude galaxy 2MASX J07001137-6602251 in the constellation Volans at a redshift of 0.0262, around 375 million light years away. Observations in UV light made with NASA's Neil Gehrels Swift Observatory showed a drop in the temperature of the tidal disruption from around 71,500 to 35,500 degrees Fahrenheit (40,000 to 20,000 degrees Celsius) over a few days. This is the first time such an early temperature drop has been seen in a tidal disruption event. The transient resulting from the tidal disruption event has been cataloged as AT 2019ahk.
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