Evidence for Returning Disk Radiation in the Black Hole X-ray Binary XTE J1550-564

Understand

We explore the accretion properties of the black hole X-ray binary \j1550\ during its outbursts in 1998/99 and 2000.

• We model the disk, corona, and reflection components of X-ray spectra taken with the {\it Rossi X-ray Timing Explorer} (\rxte), using the {\tt relxill} suite of reflection models.
• The key result of our modeling is that the reflection spectrum in the very soft state is best explained by disk self-irradiation, i.e., photons from the inner disk are bent by the strong gravity of the black hole, and reflected off the disk surface.
• This is the first known detection of thermal disk radiation reflecting off the inner disk.