The optical/UV and radio emission of tidal disruption events

When the orbital pericenter of a star is equal to or smaller than the tidal radius of a black hole, the star will be tidally disrupted, triggering the so-called tidal disruption events (TDEs). The TDEs can generate electromagnetic radiation from radio to gamma ray bands. My talk focus on the optical and radio emission. The observationally inferred location of optical emission is 1014-16cm from the central super-massive black hole. However, theoretically, if the stellar debris can be circularized and form an accretion disk, the size of the disk is several times of 1013cm, which is serval orders of magnitude smaller than the observationally inferred optical radiation radius. It is proposed that the optically thick winds in the TDEs events can take gas to a significantly large radius. The X-rays can be reprocessed into optical/UV bands by the winds and finally emitted from the photosphere of the optically thick winds, which can be consistent with the observationally inferred emission radius. We perform simulations to study the optical/UV emission of TDEs. We find that the wind reprocessing model can explain the observations of the optical/UV emission of TDEs, including the emission radius, the radiation temperature and luminosity as well as their time-evolution very well. We propose that in some TDEs, the radio emission is produced in the shock process when the TDE winds collide with the dense clouds surrounding the central supermassive black hole. The wind-cloud interaction model can explain the radio peak frequency and radiation at peak frequency  and their time-evolution very well.

Defu Bu (SHAO)
Fukun Liu
Tuesday, April 11, 2023 - 4:00PM to Tuesday, April 11, 2023 - 5:00PM
I was a graduate student from 2005-2010 in Shanghai Astronomical observatory (SHAO). I got my PhD degree in 2010. Then, I work as a faculty in SHAO. I mainly works on compact object related astrophysics including AGNs, AGN feedback, tidal disruption events and black hole X-ray binaries.