Two spectral states of the transient X-ray burster SAX J1747.0-2853

Abstract

The neutron star binary SAX J1747.0-2853, located in the Galactic Center region at about 0.5 deg from Sgr A* and at a distance of 9 kpc, 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 70 keV. About two years later the source reappeared about one order of magnitude brighter in the X-rays (0.5-10 keV) 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 ~0.5 keV assuming pure blackbody). For this model, the flux of the non-thermal component below ~10 keV is a significant fraction of the total X-ray flux, i.e. greater than ~50% in the 2-10 keV band.

arXiv comment4 pages, 1 latex file, 3 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (9)

• Photospheric radius expansion X-ray bursts as standard candles
• ASCA Observations of the Sgr B2 Cloud: An X-Ray Reflection Nebula
• The Zoo of X-ray sources in the Galactic Center Region: Observations with BeppoSAX
• Long-Term X-ray Monitoring of 1E 1740.7-2942 and GRS 1758-258
• XMM-Newton study of the persistent X-ray source 1E1743.1-2843 located in the Galactic Center direction
• Chandra observations of the bursting X-ray transient SAX J1747.0-2853 during low-level accretion activity
• X-ray spectral evolution of SAX J1747.0-2853 during outburst activity and confirmation of its transient nature
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• The Spectral States of Black Hole X-ray Binary Sources

Cited by in corpus (6)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• The XMM-Newton view of the central degrees of the Milky Way
• The INTEGRAL Galactic bulge monitoring program: the first 1.5 years
• A four-year XMM-Newton/Chandra monitoring campaign of the Galactic Centre: analysing the X-ray transients
• Maxi observations of long X-ray bursts
• Temperature Measurement during Thermonuclear X-ray Bursts with BeppoSAX