Letter to the Editor

XMMU J174716.1–281048: a “quasi-persistent” very faint X-ray transient?

¹ Istituto di Astrofisica Spaziale e Fisica Cosmica di Roma – INAF, via del Fosso del Cavaliere 100, 40133 Roma, Italy e-mail: melania.delsanto@iasf-roma.inaf.it
² Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano – INAF, via E. Bassini 15, 20133 Milano, Italy
³ Universitá di Tor Vergata, Roma, Italy

Received: 23 March 2007
Accepted: 13 April 2007

Abstract

The X-ray transient XMMU J174716.1–281048 was serendipitously discovered with XMM-Newton in 2003. It lies about 0.9 degrees off the Galactic Centre and its spectrum shows a high absorption (~ cm^-2). Previous X-ray observations of the source field performed in 2000 and 2001 did not detect the source, indicative of a quiescent emission at least two orders of magnitude fainter. The low luminosity during the outburst (~³⁴ erg s^-1 at 8 kpc) indicates that the source is a member of the “very faint X-ray transients” class. On 2005 March 22nd the INTEGRAL satellite caught a possible type-I X-ray burst from the new INTEGRAL source IGR J17464–2811, classified as fast X-ray transient. This source was soon found to be positionally coincident, within the uncertainties, with XMMU J174716.1–281048. Here we report data analysis of the X-ray burst observed with the IBIS and JEM-X telescopes and confirm the type-I burst nature. We also re-analysed XMM-Newton and Chandra  archival observations of the source field. We discuss the implications of these new findings, particularly related to the source distance as well as the source classification.