Suzaku broadband spectroscopy of Swift J1753.5-0127 in the Low-Hard State

TL;DR

This study uses Suzaku broadband X-ray observations to analyze the accretion disk and corona in the black hole candidate Swift J1753.5-0127 during its low-hard state, revealing a power-law spectrum with soft excess and a relativistic iron line.

Contribution

First broadband Suzaku spectrum of Swift J1753.5-0127 in the low-hard state, providing detailed insights into disk radius and reflection features.

Findings

Spectrum consistent with a power-law (γ ~ 1.63)

Detection of soft X-ray excess indicating a cool accretion disk

Relativistically broadened iron line suggesting inner disk radius > ISCO

Abstract

We present Suzaku observations of the Galactic black hole candidate Swift J1753.5-0127 in the low-hard state. The broadband coverage of Suzaku enables us to detect the source over the energy range 0.6 -- 250 keV. The broadband spectrum (2 -- 250 keV) is found to be consistent with a simple power-law (gamma \sim 1.63). In agreement with previous observations of this system, a significant excess of soft X-ray flux is detected consistent with the presence of a cool accretion disc. Estimates of the disc inner radius infer a value consistent with the ISCO (R_{in} \lesssim 6 R_g, for certain values of, e.g. N_H, i), although we cannot conclusively rule out the presence of an accretion disc truncated at larger radii (R_{in} \sim 10 - 50 R_g). A weak, relativistically-broadened iron line is also detected, in addition to disc reflection at higher energy. However, the iron-K line profile favours an inner radius larger than the ISCO (R _{in} \sim 10 - 20 R_g). The implications of these observations for models of the accretion flow in the low-hard state are discussed.