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

S. Mereghetti·D. I. Cremonesi·F. Haardt·T. Murakami·T. Belloni·A. Goldwurm
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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.

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S. Mereghetti, D. I. Cremonesi, F. Haardt, T. Murakami, T. Belloni, A. Goldwurm. 1996-09-06. ASCA observations of the galactic bulge hard x-ray source GRS 1758--258. https://doi.org/10.1086/303659

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