Observations of hard galactic center source 1E1740.7-2942 with ART-P/Granat

• Published in: Advances in space research Vol. 15; no. 5; pp. 115 - 118
• Main Authors: Grebenev, S.A, Pavlinsky, M.N, Sunyaev, R.A
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-01-1995
• ISSN: 0273-1177; 1879-1948
• DOI: 10.1016/0273-1177(94)00048-6

The Galactic center region hard X-ray source 1E1740.7-2942 has been intensively observed with the instuments aboard
Granat. We present here the results obtained with the ART-P coded-mask telescope in the 2.5–35 keV energy band. During 1990–1992 the source was found to be in four apparently different states of intensity corresponding to different epochs of the light curve. In the normal state its spectrum could be represented with a simple power law model (the best-fit photon index
α ⋍ −1.35±0.09) modified by strong photoabsorption at low energies (the hydrogen column density
N
H
⋍ (9.4±3.1) × 10
22
atoms cm
−2
). The effects of X-ray scattering and absorption in the molecular cloud discovered in the direction to 1E1740.7-2942 are discussed.