Out of this world: A star supposedly the size of the Sun was consumed by a black hole with nearly six million times more mass and spotted on January 21, 2019 by NASA's planet-hunting Transiting Exoplanet Survey Satellite (TESS). Over a week later, the event was bright enough to be detected by ASAS-SN's network of robotic telescopes. Follow-up observations were also made by NASA's Neil Gehrels Swift Observatory, XMM-Newton of the European Space Agency and other telescopes of the Las Cumbres Observatory network.
A tidal disruption event occurred 375 million light-years away in the Volans constellation that saw a black hole destroying a star which astronomers estimate was the size of our Sun.
The event was initially captured by NASA's TESS planet-hunting mission with follow-up discoveries by the ground based All-Sky Automated Survey for Supernovae (ASAS-SN). Thomas Holoein, a Carnegie Fellow at the Carnegie Observatories in Pasadena, California, led the study of this event, called ASASSN-19bt, and published his findings in the September 27, 2019, issue of The Astrophysical Journal.
"TESS data let us see exactly when this destructive event, named ASASSN-19bt, started to get brighter, which we've never been able to do before," said Holoein. He was able to conduct multiwavelength follow-up observations of the tidal disruption in the first few days as the event was quickly identified by ASAS-SN's network of telescopes on January 29.
Although TESS made the observation over a week earlier, NASA says the satellite only transmits data to Earth every two weeks, after which it needs to be processed at the agency's Ames Research Center in Silicon Valley. It wasn't until March 13 that the first TESS data on this tidal disruption became available.
"The early TESS data allow us to see light very close to the black hole, much closer than we've been able to see before," said Patrick Vallely, a co-author and National Science Foundation Graduate Research Fellow at Ohio State University, which is also the headquarters of ASAS-SN. He further commented that the smooth rise in the brightness of ASASSN-19bt supported the fact that the event was indeed a tidal disruption and not another type of outburst.
UV data from the Swift Observatory was used in determining a sharp temperature drop of 50 percent, which went from around 71,500 °F to 35,000 °F (40,000 °C to 20,000 °C) in just over a few days. Holoein observed that it was the first time such an early temperature decrease was seen in a tidal disruption, something he said had been predicted in earlier theories.
"Tidal disruptions are incredibly rare, occurring once every 10,000 to 100,000 years in a galaxy the size of our own Milky Way." stated NASA's Goddard Space Flight Center. "For TESS to observe ASASSN-19bt so early in its tenure, and in the continuous viewing zone where we could watch it for so long, is really quite extraordinary," said Padi Boyd, TESS' project scientist at Goddard further adding that "future collaborations with observatories around the world and in orbit will help us learn even more about the different outbursts that light up the cosmos."