SIMBAD references

2020ApJ...889L..18Y - Astrophys. J., 889, L18-L18 (2020/January-3)

Coronal properties of black hole X-ray binaries in the hard state as seen by NuSTAR and Swift.

YAN Z., XIE F.-G. and ZHANG W.

Abstract (from CDS):

In this work we measure two important phenomenological parameters of corona (and hot accretion flow) in black hole X-ray binaries: the photon index Γ and the electron temperature kTe. Thanks to the capability of the Nuclear Spectroscopic Telescope Array in hard X-rays, we measure these two parameters over six orders of magnitude in the 0.1-100 keV X-ray luminosity Lx, from ∼5 x 1038 ergs–1 down to as low as ∼5 x 1032 ergs–1. We confirm the existence of a "V"-shaped correlation between Γ and Lx. Surprisingly, we observe a "Λ"-shaped correlation between kTe and Lx. The "cooler when brighter" branch in the high-luminosity regime (Lx >= 3 x 1036 ergs–1) agrees with previous results and can be understood under the existing model of Compton scattering in the corona. On the other hand, the apparent "cooler when fainter" (positive kTe-Lx correlation) branch in the low-luminosity regime (Lx <= 3 x 1036 ergs–1) is unexpected, thus it puts a new challenge to existing models of hot accretion flow/corona.

Abstract Copyright: © 2020. The American Astronomical Society. All rights reserved.

Journal keyword(s): Accretion - black hole physics - X-ray binary stars - Black holes - Compact objects - High energy astrophysics - Compact binary stars

Simbad objects: 20

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