Central Bureau for Astronomical Telegrams
IAUC 5749: GRB 930309
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Circular No. 5749
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@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
GRB 930309
The COMPTEL team (K. Bennett, Astrophysics Division, Space
Science Department, ESTEC, European Space Agency; V. Schonfelder,
Max-Planck-Institut fur Extraterrestrische Physik; J. Ryan, University
of New Hampshire; W. Hermsen, SRON Laboratory for Space Research,
Leiden; and their colleagues) reports: "We have imaged a
gamma-ray burst at > 1 MeV. The event was detected by BATSE on
Mar. 9.13053 UT and was of about 20 s duration in the COMPTEL data.
The imaging analysis is preliminary, and because of limited counts,
the error in position is larger than the nominal COMPTEL resolution
of 1 deg. The most likely position of the burst is R.A. =
21h32m31s, Decl. = +54 39'.0 (equinox 2000.0). The four corners of
the 1-sigma error box are: 21h40m00s, +55 25'.2; 21h38m07s,
+53 15'.6; 21h27m07s, +53 19'.8; 21h27m22s, +55 30'.0. Because of
the proximity of the sun in early March, the field was poorly
observable with optical instruments. Only radio observatories who
expressed interest were notified as part of the COMPTEL/NMSU Rapid
Burst Response Campaign. However, new observations are encouraged.
Interested observers can contact Ryan (e-mail jryan@unh.edu;
telephone 603-862-3510) or B. McNamara at New Mexico State University
(e-mail bmcnamar@nmsu.edu; telephone 505-646-2614)."
L. Hanlon and K. Bennett (ESA/ESTEC), with T. Spoelstra
(Dwingeloo), communicate: "We report the detection of a possible
radio counterpart of the gamma-ray burst GRB 930309. The radio
source is located at R.A. = 21h32m39s.0, Decl. = +54 38'34" (equinox
2000.0; the positional error is within the least significant
digit). This is close to the COMPTEL maximum likelihood position
given above. Radio observations of the GRB error box began on Mar.
12 (at 49 cm), with subsequent observations on Mar. 16 (49 cm) and
18 (6 cm). The source was initially observed to have a flux of 76
+/- 3.6 mJy at 49 cm. Three days later, the flux had declined to
66 +/- 2.9 mJy. The observation at 6 cm gives an upper limit on
the flux of 1 mJy, indicating that the source has an unusually
steep spectral slope. Monitoring at 49 cm is still in progress. In
view of the pressing need to identify the nature of gamma-ray
bursts we encourage complementary observations of this source at
other wavelengths."
1993 April 5 (5749) Daniel W. E. Green
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