2004A&A...416..699N

The neutron star binary SAX J1747.0-2853, located in the Galactic Center region at about 0.5° from Sgr A* and at a distance of ∼9kpc, has been observed in outburst four times (1998, 1999, 2000 and 2001) by BeppoSAX and RossiXTE. At the time of its discovery in 1998 the source was observed in a low/hard state, showing a hard tail with a high energy cutoff of ∼70keV. About two years later the source reappeared about one order of magnitude brighter in the X-rays (0.5-10keV) and with a significantly steeper spectrum. As was the case for the low state, the data could be fitted by an input model based on two continuum primary components: a) a soft thermal excess, which is ∼4 times more luminous than the one found in hard state; b) a non-thermal component which is compatible with either a power-law or a comptonization spectrum. The soft component is equally well described by pure blackbody or multi-color disk emission, with significantly higher temperature than observed in low state (∼1.3 vs. the ∼0.5keV assuming pure blackbody). For this model, the flux of the non-thermal component below ∼10keV is a significant fraction of the total X-ray flux, i.e. greater than ∼50% in the 2-10keV band.