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IAUC 6083: KS 1730-312; X-RAY N 1993 IN Oph

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                                                  Circular No. 6083
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505

KS 1730-312
     K. Borozdin, N. Alexandrovich, V. Arefiev and R. Sunyaev, Space
Research Institute, Moscow, on behalf of the MIR-KVANT-TTM team,
communicate: "During observations of the Galactic Center field by the
TTM coded-mask instrument onboard the MIR space station on Sept. 23, a
flux of 70 +/- 10 mCrab within the energy band 2-30 keV was detected from
R.A. = 17h30m.3, Decl. = -31d11' (equinox 1950.0, uncertainty +/- 2').
The source spectrum can be approximated by a power law with spectral
index -1.9 +/- 0.4."

     E. Churazov, M. Gilfanov, J. Ballet and E. Jourdain, on behalf of
the Granat Team (Space Research Institute, Moscow; Service d'Astrophysique,
Centre d'Etudes de Saclay; and Centre d'Etude Spatiale des Rayonnements,
Toulouse), report: "During observations of the Galactic Center region
on Sept. 22-23 the SIGMA telescope onboard Granat Observatory detected
a new hard x-ray source that is compatible with the above position.
The 40-150-keV flux from the source was about 130 mCrab.  No significant
emission from this source has been detected by SIGMA in previous
observations, performed during Sept. 1-22 with 3-sigma upper limits of
40 mCrab (Sept. 20-22) and 15 mCrab (Sept. 1-22).  In subsequent
observations on Sept. 24-25 and 25-26 the source flux was 116 and 93
mCrab, respectively.  Gradual softening of the spectrum has been observed
with the power-law photon index changing from 2.2 +/- 0.2 on Sept. 22-23
to 2.9 +/- 0.5 on Sept. 25-26."

     Churazov et al. add: "In the course of the same set of Galactic
Center observations SIGMA detected hard x-ray emission from the x-ray
nova observed in Ophiuchus in 1993 (cf. IAUC 5874, 5876, et seq.;
R.A. = 17h16m.5, Decl. = -24d58', equinox 1950.0).  The source was present
in the 40-150-keV band during the whole interval 1994 Sept. 1-23.  The
time-averaged flux from the source is about 110 mCrab.  A power-law
approximation to the source spectrum gives the photon index 2.3 +/- 0.3."

     Borozdin and Alexandrovich report: "The TTM coded-mask instrument
onboard MIR registered x-ray emission from the direction of the 1993
x-ray nova with flux 55 +/- 15 mCrab (at 2-30 keV), averaged over
observations on 1994 Aug. 31, Sept. 1 and 23.  The photon index of the
power-law approximation is 2.0 +/- 0.7."

1994 September 30              (6083)              Brian G. Marsden

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