X-ray and Optical Observations of the Black Hole Candidate MAXI J1828-249

Understand

We report results from X-ray and optical observations of the Galactic black hole candidate MAXI J1828-249, performed with Suzaku and the Kanata telescope around the X-ray flux peak in the 2013 outburst.

• The time-averaged X-ray spectrum covering 0.6--168 keV was approximately characterized by a strong multi-color disk blackbody component with an inner disk temperature of ~0.6 keV, and a power-law tail with a photon index of ~2.0.
• We detected an additional structure at 5-10 keV, which can be modelled neither with X-ray reflection on the disk, nor relativistic broadening of the disk emission.
• Instead, it was successfully reproduced with a Comptonization of disk photons by thermal electrons with a relatively low temperature (<~10 keV).