XMM-Newton and INTEGRAL observations of the very faint X-ray transient IGR J17285−2922/XTE J1728−295 during the 2010 outburst

• Published in: Monthly notices of the Royal Astronomical Society Vol. 415; no. 3; pp. 2373 - 2378
• Main Authors: Sidoli, L., Paizis, A., Mereghetti, S., Götz, D., Del Santo, M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 11.08.2011; Wiley-Blackwell
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; X-rays: binaries; X-rays: individual: IGR J17285−2922; X-rays: individual: XTE J1728−295; X-rays: binaries; X-rays: individual: IGR J17285−2922; X-rays: individual: XTE J1728−295; Uncertainty; Black holes; Binary X ray source; Cosmic x-ray sources; X-rays: individual: XTEJ 1728-295; Compact stars; Column density; X-rays: individual: IGR J17285―2922; Compact objects; X-ray binary stars; Power law; Spectroscopy; Neutron stars; X ray observation; INTEGRAL satellite; Power spectra; X-ray spectra; Milky Way; Transient X ray source; X ray pulsation; Type I X ray burst; Low-mass stars; Galactic bulge; Cosmology; Timing; Simultaneous observation
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1111/j.1365-2966.2011.18865.x

We report the first broad-band (0.5-150 keV) simultaneous X-ray observations of the very faint X-ray transient IGR J17285−2922/XTE J1728−295 performed with the 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 22 ks. 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 Γ of 1.61 ± 0.01, an absorbing column density N H of (5.10 ± 0.05) × 1021 cm−2 and a flux of 2.4 × 10−10 erg cm−2 s−1 (1-100 keV), corrected for the absorption. The data did not require either a spectral cut-off (Ec > 50 keV) or an additional soft component. The slopes of the power law fitting 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 is 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 report here allow us to conclude that IGR J17285−2922 is a low-mass X-ray binary, located at a distance greater than 4 kpc.