Modeling X-ray reflection spectra from disk returning radiation: Application to 4U 1630-47

Abstract

Returning radiation is thought to play a key role in disk illumination of black-hole X-ray binaries in the high-soft state, yet it has not been fully incorporated into XSPEC reflection models. We present a new table model for reflection spectroscopy that self-consistently accounts for the returning radiation of the thermal component. To isolate this effect, we adopted the standard disk-corona configuration but disabled the corona, allowing the reflection spectrum to be produced solely by the self-irradiation of the disk. We applied our model to three NICER and NuSTAR simultaneous observations of the black-hole X-ray binary 4U 1630-47 during the soft state. The model fits the data well, suggesting that returning radiation from the disk could potentially explain the reflection features observed in this source. Our results suggest a rapidly spinning black hole ($a_{\ast }\sim 0.99$), a disk inclination of $i\sim 43^{\circ }-54^{\circ }$, a mass accretion rate of ${\dot{M}}_{\mathrm{BH}}\sim (0.13-0.25){\dot{M}}_{\mathrm{Edd}}$, and a source distance of $7.3-11.3\mathrm{kpc}$, which is in broad agreement with previous studies.

arXiv comment16 pages, 10 figures, 5 tables