2004A&A...416..311W

SAX J1747.0-2853 is an X-ray transient which exhibited X-ray outbursts yearly between 1998 and 2001, and most probably also in 1976. The outburst of 2000 was the longest and brightest. We have analyzed X-ray data sets that focus on the 2000 outburst and were obtained with BeppoSAX, XMM-Newton and RXTE. The data cover unabsorbed 2-10keV fluxes between 0.1 and 5.3x10^–9erg/s/cm². The equivalent luminosity range is 6x10³⁵ to 2x10³⁷erg/s. The 0.3-10keV spectrum is well described by a combination of a multi-temperature disk blackbody, a hot Comptonization component and a narrow Fe-K emission line at 6.5 to 6.8keV with an equivalent width of up to 285eV. The hydrogen column density in the line of sight is (8.8±0.5)x10²²/cm². The most conspicuous spectral changes in this model are represented by variations of the temperature and radius of the inner edge of the accretion disk, and a jump of the equivalent width of the Fe-K line in one observation. Furthermore, 45 type-I X-ray bursts were unambiguously detected between 1998 and 2001 which all occurred during or close to outbursts. We derive a distance of 7.5±1.3kpc which is consistent with previous determinations. Our failure to detect bursts for prolonged periods outside outbursts provides indirect evidence that the source returns to quiescence between outbursts and is a true transient.