Central Bureau for Astronomical Telegrams
IAUC 5358: 1991ba; GAMMA-RAY BURSTS
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Read IAUC 5359
Circular No. 5358
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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
MARSDEN or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN
SUPERNOVA 1991ba IN ESO 244-IG32
R. H. McNaught, Anglo-Australian Observatory, reports his
discovery of an apparent supernova (mag about 18.5) in the irregular
galaxy ESO 244-IG32. The image appears on a V plate taken by S. M.
Hughes with the U.K. Schmidt Telescope on Oct. 2.6 UT. Located at
R.A. = 1h28m36s.57, Decl. = -42 42'58".6 (equinox 1950.0, uncertainty
0".6 in each coordinate), the supernova lies on the brighter,
western edge of the galaxy. It is offset from the center of the
galaxy (there being no obvious nucleus) by 1" west and 11" north.
No star appears in this position on the ESO B or R surveys (the galaxy
is heavily overexposed on the SERC J survey). A nearby star of
mag about 15 is located at R.A. = 1h28m31s.22, Decl. = -42 43'39".0.
GAMMA-RAY BURSTS
C. A. Meegan, G. J. Fishman, R. B. Wilson, W. S. Paciesas, M.
N. Brock, J. M. Horack, G. N. Pendleton, and C. Kouveliotou report,
for the BATSE Science Team: "The BATSE experiment on the Compton
Gamma Ray Observatory has detected 132 cosmic gamma-ray bursts from
Apr. 24 through Oct. 1. The sky exposure has been measured; the
largest deviation from non-uniformity is an enhanced exposure of
about 20 percent in the direction of the celestial poles relative to
the equator. The BATSE burst location accuracy is typically 5 to 10
degrees, as determined from BATSE observations of solar flares and
from bursts independently located by other instruments. The
distribution of 117 located events is isotropic within the statistical
limits. A measure of the dipole moment with respect to the galactic
center is <cos theta> = 0.008 +/- 0.071 (vs. 0 for an isotropic
distribution). A measure of the quadrupole moment with respect to the
galactic plane is <sin2 beta> = 0.30 +/- 0.05 (vs. 1/3 for an
isotropic distribution). The only non-uniformity in the observed
distribution is consistent with the non-uniformity in the sky exposure
map. There is no apparent clustering of bursts around the LMC, M31,
or nearby clusters of galaxies. The brightness distribution of 99
analyzed bursts bursts is inconsistent with a homogeneous, isotropic
distribution. The integral brightness distribution has a slope of
about -0.8 (vs. -3/2 for a homogeneous, isotropic distribution).
The average value of V/Vmax is 0.34 +/- 0.03 (vs. 1/2 for a homogeneous,
isotropic distribution). These observations suggest a spatial
confinement of the burst sources, and are difficult to reconcile
with known distributions of galactic objects."
1991 October 4 (5358) Daniel W. E. Green
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