ASCA observations of the galactic bulge hard x-ray source GRS 1758--258

Abstract

GRS 1758-258 is one of the few persistent hard X-ray emitters (E>100 keV) in the Galaxy. Using the ASCA satellite, we have obtained the first detailed data on GRS 1758-258 in the 1-10 keV range, where previous observations were affected by confusion problems caused by the nearby strong source GX5-1. The spectrum is well described by a power law with photon index 1.7 without strong Fe emission lines. A prominent soft excess, as observed with ROSAT when the hard X-ray flux was in a lower intensity state, was not detected. However, the presence of a soft spectral component, accounting for at most 5% of the 0.1-300 keV flux, cannot be excluded. The accurate measurement of interstellar absorption (N_H=(1.5+-0.1) x 10^22 cm -2) corresponds to an optical extinction which definitely excludes the presence of a massive companion.

7 pages, AAS latex [11pt,aaspptwo,flushrt,tighten], + 1.ps figure Accepted for pubblication in ApJ, 09 02 96 Also available at http://fy.chalmers.se/~haardt/personal/curr.html Figures 1 and 2 available upon request at [email protected]

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• Deep Infrared Imaging of the Microquasars 1E1740-2942 and GRS 1758-258
• Long-term Multi-wavelength Observations of GRS 1758-258 and the ADAF Model
• Identification of the optical and near-infrared counterpart of GRS 1758-258
• XMM-Newton Spectroscopy of the Galactic Microquasar GRS 1758-258 in the Peculiar Off/Soft State
• Broadband X-ray properties of black holes GRS 1758-258 and 1E 1740.7-2942: AstroSat and NuSTAR results
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