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IAUC 5310: 1991al; N Mus 1991

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                                                  Circular No. 5310
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

     L. Wells, Cerro Tololo Interamerican Observatory; and J. Maza,
University of Chile, report the discovery by M. Wischnjewsky (
University of Chile) of a supernova located about 17" east and 5" south
of the nucleus of an anonymous galaxy at R.A. = 19h38m.3, Decl. =
-55 13' (equinox 1950.0).  The supernova (mpg about 16) was found on
a 20-min unfiltered IIa-O plate taken by L. Wells (CTIO) and R.
Antezana (University of Chile) with the CTIO Curtis Schmidt telescope
on July 16.2 UT.  Confirmation was made by H. Yee (University
of Toronto) and E. Ellingson (Dominion Astrophysical Observatory)
from B and Gunn-R CCD images obtained on July 17.16 with the CTIO
0.91-m telescope.  The galaxy has an elongated nucleus and spiral
arms of very low surface brightness.

     R. Sunyaev, J. P. Roques, and A. Goldwurm, on behalf of the
Granat team (Space Research Institute, Moscow; Centre d'Etude
Spatiale des Rayonnements, Toulouse; Service d'Astrophysique du CEA,
Saclay), report:  "GRS 1124-684 (Nova Mus 1991) was observed on May
31 and was detected by both the ART-P and SIGMA instruments.  In the
ART-P 5- to 30-keV spectral band, the source was detected at the
level of 60 mCrab.  It had a Crab-like spectrum with a photon index
2.24 +/- 0.04; the flux at 10 keV was (5.0 +/- 0.4) x 10E-3 photons
cmE-2 sE-1 keVE-1.  According to SIGMA 35- to 200-keV data, the
source flux at 100 keV was (3.9 +/- 0.7) x 10E-5 photons cmE-2 sE-1
keVE-1 at a power law index 2.3 +/- 0.4.  Although 5 months had
passed since the outburst, this source remained very bright in a
broad x-ray band.  Its luminosity was estimated as (1.5 +/- 0.1) x
10E35, (8.2 +/- 1.2) x 10E34, and (3.9 +/- 1.7) x 10E34 erg/s,
respectively, in 5- to 30-, 35- to 100-, and 100- to 200-keV bands
(assuming a distance of 1 kpc).  These values are only four to five
times lower than those obtained during the second half of January
(IAUC 5176).  Thus, the hard x-ray light curve does not exhibit the
exponential decay, with folding time of the order of 30 days, that
was detected by GINGA for soft x-ray component."

1991 July 18                   (5310)             Daniel W. E. Green

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