Long-Term Variability of the Hard X-ray Source GRS 1758-258

  title={Long-Term Variability of the Hard X-ray Source GRS 1758-258},
  author={S. E. Kuznetsov and Marat Gilfanov and Evgenii M. Churazov and Rashid Alievich Sunyaev and A. V. D’yachkov and N. G. Khavenson and B. S. Novikov and Kirill Sukhanov and Jean Ballet and Ph. M. Laurent and Bertrand Cordier and Andrea Goldwurm and Jean Pierre Roques and Elisabeth Jourdain and Laurent Bouchet and Gilbert Vedrenne},
The results of hard x-ray observations of GRS 1758-258 in 1990–1997 by GRANAT/SIGMA are presented. The long-term light curve of the source shows variations in the 40–200 keV luminosity by a factor of more than ~ 7 — from less than 1.5 × 1036 erg s−1 up to 10 × 1036 erg s−1. The average 40–200 keV luminosity is ~ 6 × 1036 erg s−1 and the averaged spectrum has best-fit power-law photon index α = 2.00 ± 0.06 with a steepening above ~ 100 keV. The source long-term light curve and the spectrum are… CONTINUE READING


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