Abstract The field containing the newly discovered soft γ-ray source GRS 1758-258, located 40 arcmin. away from GX 5-1, was observed by the SIGMA telescope on board the soviet spacecraft GRANAT in the course of the five extensive galactic-center surveys performed in 1990, 1991 and 1992. In both 1990 surveys, as well as in the February–April 1991 survey, the source exhibits a Cygnus X-1 like spectrum with nearly constant flux, while in the most recent measurements on September–October 1991 and spring 1992, a long term low-state has been discovered with an upper limit on the source flux five time lower than the average flux measured by SIGMA during all the observations from March 1990 until April 1991.
SIGMA observations of the soft Gamma-Ray Source GRS 1758-258
Advances in Space Research ; 13 , 12 ; 751-754
1993-01-01
4 pages
Article (Journal)
Electronic Resource
English
SIGMA Observations of the Soft Gamma-Ray Source GRS 1758-258
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