X-ray Brightening and UV Fading of Tidal Disruption Event ASASSN-15oi

Dec 11, 2017
6 pages
Published in:
  • Astrophys.J.Lett. 851 (2017) 2, L47
  • Published: Dec 21, 2017
e-Print:

Citations per year

Loading ...
Abstract: (IOP)
We present late-time observations by Swift and XMM-Newton of the tidal disruption event (TDE) ASASSN-15oi that reveal that the source brightened in the X-rays by a factor of ∼10 one year after its discovery, while it faded in the UV/optical by a factor of ∼100. The XMM-Newton observations measure a soft X-ray blackbody component with , corresponding to radiation from several gravitational radii of a central black hole. The last Swift epoch taken almost 600 days after discovery shows that the X-ray source has faded back to its levels during the UV/optical peak. The timescale of the X-ray brightening suggests that the X-ray emission could be coming from delayed accretion through a newly forming debris disk and that the prompt UV/optical emission is from the prior circularization of the disk through stream–stream collisions. The lack of spectral evolution during the X-ray brightening disfavors ionization breakout of a TDE “veiled” by obscuring material. This is the first time a TDE has been shown to have a delayed peak in soft X-rays relative to the UV/optical peak, which may be the first clear signature of the real-time assembly of a nascent accretion disk, and provides strong evidence for the origin of the UV/optical emission from circularization, as opposed to reprocessed emission of accretion radiation.
Note:
  • Accepted for publication in ApJ Letters
  • accretion, accretion disks
  • black hole physics
  • galaxies: nuclei
Loading ...