X-ray spectral evolution of SAX J1747.0-2853 during outburst activity and confirmation of its transient natureReport as inadecuate



 X-ray spectral evolution of SAX J1747.0-2853 during outburst activity and confirmation of its transient nature


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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 2-10 keV fluxes between 0.1 and 5.3 X 10^-9 erg-s-cm^2. The equivalent luminosity range is 6 X 10^35 to 2 X 10^37 erg-s. The 0.3-10 keV 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 6.8 keV with an equivalent width of up to 285 eV. The hydrogen column density in the line of sight is 8.8+-0.5 X 10^22 cm^-2. 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+-1.3 kpc 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.



Author: N. Werner; J. J. M. in 't Zand; L. Natalucci; C. B. Markwardt; R. Cornelisse; A. Bazzano; M. Cocchi; J. Heise; P. Ubertini

Source: https://archive.org/



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