XMM-Newton observations of the INTEGRAL X-ray transient IGR J17544-2619

Free access article

Issue		A&A Volume 420, Number 2, June III 2004


Page(s)		589 - 594
Section		Stellar structure and evolution
DOI		http://dx.doi.org/10.1051/0004-6361:20035940

A&A 420, 589-594 (2004)
DOI: 10.1051/0004-6361:20035940

XMM-Newton observations of the INTEGRAL X-ray transient IGR J17544-2619

R. González-Riestra¹, T. Oosterbroek², E. Kuulkers², A. Orr² and A. N. Parmar³

¹ XMM-Newton Science Operation Centre, ESA, VILSPA, PO Box 50727, 28080 Madrid, Spain
² INTEGRAL Science Operations Centre, Science Operations and Data Systems Division, Research and Scientific Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
³ Astrophysics Missions Division, Research and Scientific Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands

(Received 17 November 2003 / Accepted 12 February 2004 )

Abstract
On September 17, 2003 INTEGRAL discovered a bright transient source 3 $\degr$ from the Galactic Center, IGR J17544-2619 . The field containing the transient was observed by XMM-Newton on March 17 and September 11 and 17, 2003. A bright source, at a position consistent with the INTEGRAL location, was detected by the European Photon Imaging Camera (EPIC) during both September observations with mean 0.5-10 keV unabsorbed luminosities of $1.1\times10^{35}$ and $5.7\times10^{35}$ erg s ^-1 for an (assumed) distance of 8 kpc. The source was not detected in March 2003, with a 0.5-10 keV luminosity of < $3.8 \times10^{32}$ erg s ^-1. The September 11 and 17 EPIC spectra can be represented by a power-law model with photon indices of $2.25\pm0.15$ and $1.42\pm0.09$ , respectively. Thus, the 0.5-10 keV spectrum hardens with increasing intensity. The low-energy absorption during both September observations is comparable to the interstellar value. The X-ray lightcurves for both September observations show energy dependent flaring which may be modeled by changes in either low-energy absorption or power-law index.

Key words: accretion, accretion disks -- X-rays: individuals: IGR J17544-2619 -- stars: neutron -- X-rays: binaries

Offprint request: R. González-Riestra, rgonzale@xmm.vilspa.esa.es

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