A strong and broad iron line in the XMM-Newton spectrum of the new X-ray transient and black-hole candidate XTE J1652-453

TL;DR

This study analyzes X-ray spectra of the black-hole candidate XTE J1652-453, revealing a broad iron emission line indicative of relativistic reflection near the black hole, and estimates its spin and accretion disk properties.

Contribution

First detailed spectral analysis of XTE J1652-453 during decay, showing relativistic broad iron line and constraining black hole spin and disk geometry.

Findings

Detected a strong, broad iron emission line (~450 eV)

Estimated black hole spin parameter ~ 0.5

Identified variability features consistent with a hard-intermediate state

Abstract

We observed the new X-ray transient and black-hole candidate XTE J1652-453 simultaneously with XMM-Newton and the Rossi X-ray Timing Explorer (RXTE). The observation was done during the decay of the 2009 outburst, when XTE J1652-453 was in the hard-intermediate state. The spectrum shows a strong and broad iron emission line with an equivalent width of ~ 450 eV. The profile is consistent with that of a line being produced by reflection off the accretion disk, broadened by relativistic effects close to the black hole. The best-fitting inner radius of the accretion disk is ~ 4 gravitational radii. Assuming that the accretion disk is truncated at the radius of the innermost stable circular orbit, the black hole in XTE J1652-453 has a spin parameter of ~ 0.5. The power spectrum of the RXTE observation has an additional variability component above 50 Hz, which is typical for the hard-intermediate state. No coherent quasi-periodic oscillations at low frequency are apparent in the power spectrum, which may imply that we view the system at a rather low inclination angle.