Speaker
Description
The nature of the state transition of black hole X-ray binaries has been debated for decades. We present an analysis of the relativistic reflection spectra of GX 339–4 during the hard-to-soft transition of its 2021 outburst observed by Insight–HXMT. The transition is accompanied by an increasing temperature of the disk and a softening of the corona emission, while the inner disk radius remains stable. If we include the Comptonization of the reflection spectrum, the scattering fraction parameter is found to decrease during the state transition. Our results support the scenario in which the state transition is associated with variations in the corona properties. The data also allow to measure parameters of the system, e.g. we find a high black hole spin (a* > 0.86) and an intermediate disk inclination angle (i ~ 35–43 deg) of the system.
