Looking for black-holes in X-ray binaries with XMM-Newton: XTE J1817-330 and XTE J1856+053

TL;DR

This study used XMM-Newton observations to analyze two X-ray transients, XTE J1817-330 and XTE J1856+053, providing evidence for stellar black holes in both systems through their soft X-ray spectra.

Contribution

First XMM-Newton targeted observations of these transients to identify black hole signatures, confirming their nature as stellar black holes.

Findings

Soft X-ray spectra indicate black hole presence

Both systems host accreting stellar black holes

Observations constrain system parameters

Abstract

The X-ray binary XTE J1817-330 was discovered in outburst on 26 January 2006 with RXTE/ASM. One year later, another X-ray transient discovered in 1996, XTE J1856+053, was detected by RXTE during a new outburst on 28 February 2007. We triggered XMM-Newton target of opportunity observations on these two objects to constrain their parameters and search for a stellar black holes. We summarize the properties of these two X-ray transients and show that the soft X-ray spectra indicate indeed the presence of an accreting stellar black hole in each of the two systems.