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IAUC 5874: GRS 1716-249 = GRO J1719-24; 1993J

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                                                  Circular No. 5874
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

GRS 1716-249 = GRO J1719-24
     J. Ballet, M. Denis, M. Gilfanov, and R. Sunyaev, on behalf of
the SIGMA/GRANAT Team (Service d'Astrophysique, Centre d'Etudes de
Saclay; Centre d'Etude Spatiale des Rayonnements, Toulouse; Space
Research Institute, Moscow), report:  "A new hard x-ray transient
(GRS 1716-249) in Ophiuchus has been discovered by SIGMA/GRANAT,
during an observation of the Galactic Center region performed on
Sept. 25-26.  A preliminary analysis revealed the source at R.A. =
17h16m40s.8, Decl. = -24o55'12" (equinox 1950.0; typical 90-percent
confidence error circle radius of 3').  The source spectrum was
found to be particularly hard, reminiscent of 1E 1740.7-2942, with
flux levels of 342 +/- 45, 380 +/- 46, and 294 +/- 85 mCrab in the
energy bands 35-75, 75-150, and 150-300 keV, respectively.  The
source intensity remained constant during the whole observation.
The source was not detected in the previous SIGMA observation of
the Galactic Center region performed on Sept. 18-19, with 2-sigma
upper limits of 50, 58, and 150 mCrab in the same three energy
bands, respectively."
     B. A. Harmon, Marshall Space Flight Center (MSFC), NASA; S. N.
Zhang, Universities Space Research Association; W. S. Paciesas,
University of Alabama, Huntsville; and G. J. Fishman, MSFC, report
for the Compton Observatory BATSE Team:  "A new hard x-ray transient
has been discovered using earth-occultation monitoring on Sept.
25 in the energy range 20-320 keV.  Its location is R.A. = 17h19m.2,
Decl. = -24o24' (equinox 2000.0) with a 1-sigma error box having
the following corners:  R.A. = 17h24m.4, Decl. = -26o12'; 17h17m.6,
-24o30'; 17h11m.2, -21o18'; 17h20m.0, -24o00'.  The spectrum is
hard, with power law number index -2.0 in the band 20-100 keV;
however, the broad-band spectrum is better fit with a thermal
bremsstrahlung model with temperature kT = 70-100 keV.  The temperature
decreases with increasing intensity.  The light curve shows the
source becoming visible late on Sept. 24, with the following
average intensities relative to the Crab at 20-100 keV (+/- 20
percent): Sept. 24, 0.07; 25, 0.46; 26, 0.82; 27, 1.1; 28, 1.2.  Fast
intensity variations on the order of seconds are also observed.
Monitoring of the source is continuing."

     Visual magnitude estimates (cf. IAUC 5788):  Sept. 18.97 UT,
14.5 (B. H. Granslo, Fjellhamar, Norway); 28.13, 14.3 (H. Dahle,
Oslo, Norway).

1993 October 4                 (5874)            Daniel W. E. Green

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