XMM-Newton and INTEGRAL observations of the very faint X-ray transient IGRJ17285-2922/XTEJ1728-295 during the 2010 outburst

TL;DR

This study presents simultaneous broad-band X-ray observations of the faint transient IGRJ17285-2922 during its 2010 outburst, revealing a low hard state spectrum typical of a low mass X-ray binary, but without definitive evidence of the compact object type.

Contribution

First simultaneous broad-band X-ray spectral and timing analysis of IGRJ17285-2922 during outburst, characterizing its spectral state and constraining its nature as a low mass X-ray binary.

Findings

Spectrum fits an absorbed power law with photon index 1.61

No evidence of X-ray pulsations or bursts

Indicates a low hard state, distance >4 kpc

Abstract

We report the first broad-band (0.5-150 keV) simultaneous X-ray observations of the very faint X-ray transient IGRJ17285-2922/XTEJ1728-295 performed with XMM-Newton and INTEGRAL satellites during its last outburst, started on 2010, August 28. XMM-Newton observed the source on 2010 September 9-10, for 22ks. INTEGRAL observations were part of the publicly available Galactic Bulge program, and overlapped with the times covered by XMM-Newton. The broad-band spectroscopy resulted in a best-fit with an absorbed power law displaying a photon index of 1.61+/-0.01, an absorbing column density of (5.10+/-0.05)E21 cm-2, and a flux of 2.4E-10 erg/cm2/s (1-100 keV), corrected for the absorption. The data did not require either a spectral cut-off (E>50 keV) or an additional soft component. The slopes of the XMM-Newton and INTEGRAL separate spectra were compatible, within the uncertainties. The timing analysis does not show evidence either for X-ray pulsations or for type I X-ray bursts. The broad band X-ray spectrum as well as the power density spectrum are indicative of a low hard state in a low mass X-ray binary, although nothing conclusive can be said about the nature of the compact object (neutron star or black hole). The results we are reporting here allow us to conclude that IGRJ17285-2922 is a low mass X-ray binary, located at a distance greater than 4 kpc.