GRS 1758-258
ATel #185; R. Sunyaev (IKI, Moscow/MPA, Garching), A. Lutovinov (IKI, Moscow), S. Molkov (IKI, Moscow)
on 29 Aug 2003; 23:42 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: A.Lutovinov (aal@hea.iki.rssi.ru)
Subjects: X-ray, Gamma Ray, Request for Observations, Black Hole
The black-hole candidate GRS1758-258 was observed with
IBIS/INTEGRAL on Aug 24-29, 2003. Comparison with
results of previous observations of this source with GRANAT/SIGMA, RXTE,
CGRO, BeppoSAX shows that current source flux in hard X-rays is close to its
maximum observed in 1990 and 1997. The averaged fluxes are equal to ~65,
80 and 115 mCrab in the 25-50, 50-100, 100-150 keV energy bands, respectively.
A preliminary spectral analysis showed that the source spectrum in the
18-150 keV band can be described by a simple power-law with a photon
index of ~1.6 or comptonisation model, that are typical for black hole
binaries in a hard state. Wellknown black-hole candidate 1E1740.7-2942
observed simultaneously has a comparable flux.
Radio and infra-red observations might give additional information
about properties of the source in the state with maximal
hard X-Ray luminosity.
