Vol 16, No 4

Jet-dominated quiescent state in black hole X-ray binaries: the cases of A0620–00 and XTE J1118+480

Qi-Xiang Yang


Abstract The radiative mechanism of black hole X-ray transients (BHXTs) in their quiescent states (defined as the 2–10 keV X-ray luminosity ≲1034 erg s−1) remains unclear. In this work, we investigate the quasi-simultaneous quiescent state spectrum (including radio, infrared, optical, ultraviolet and X-ray) of two BHXTs, A0620–00 and XTE J1118+480. We find that these two sources can be well described by a coupled accretion – jet model. More specifically, most of the emission (radio up to infrared, and the X-ray waveband) comes from the collimated relativistic jet. Emission from hot accretion flow is totally insignificant, and it can only be observed in mid-infrared (the synchrotron peak). Emission from the outer cold disk is only evident in the UV band. These results are consistent with our previous investigation on the quiescent state of V404 Cyg and confirm that the quiescent state is jet-dominated.


Keywords accretion, accretion disks — black hole physics — X-rays: binaries — stars: jets — stars: individual (A0620–00, XTE J1118+480)

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