Central Bureau for Astronomical Telegrams
IAUC 6662: GRB 970508; C/1996 J1
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Circular No. 6662
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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GRB 970508
D. A. Frail, National Radio Astronomy Observatory; S. R.
Kulkarni, California Institute of Technology; and the members of
the BeppoSAX GRB Team report: "Observations with the Very Large
Array of a region that includes the new x-ray source 1SAX
J0653.8+7916 (IAUC 6656) and the optical transient (IAUC 6654,
6655) have resulted in the detection of a flaring radio source. No
source was detected on May 9.06 UT (3.7 hr after the initial burst)
and May 9.84 at a frequency of 1.43 GHz; the 3-sigma upper limits
are 0.14 mJy and 0.27 mJy, respectively. On May 13.96, a compact
source, size < 1", was detected with a peak flux at 8.46 GHz of
0.43 +/- 0.03 mJy. On May 15.08, the source had increased to 0.61
+/- 0.04 mJy at the same frequency; the flux densities were 0.10
+/- 0.05 and 0.33 +/- 0.03 mJy at at 1.43 and 4.86 GHz,
respectively, on this day. From the observations of May 13, and
assuming that the flux density is a power-law function of the
frequency, we find the slope of the power law is +1.1. The best-
derived position is from the 8.46-GHz observations of May 15.08 and
is R.A. = 6h53m49s.45, Decl. = +79o16'19".5 (equinox 2000.0), with
an error of order 0".1 in both coordinates. The position of this
source coincides with the position of the optical transient
reported on IAUC 6655. The optical transient has been considered
to be a counterpart of GRB 970508. Based on the position
coincidence and the unusual flaring activity, we suggest that this
is the radio counterpart of GRB 970508. In some models, the delay
between the increased flaring of the radio transient with respect
to the optical transient yields a valuable diagnostic. Clearly,
observations at higher radio frequencies would be most valuable."
COMET C/1996 J1 (EVANS-DRINKWATER)
Z. Sekanina, Jet Propulsion Laboratory, writes: "Standard
analysis (1982, Comets, University of Arizona Press, p. 251) of the
reported separation of the two nuclei (IAUC 6653) confirms that
nucleus B is the primary component and suggests tentatively the
second half of July 1996 as the most probable time of splitting, at
a relative deceleration of about 30 units of 10E-5 the solar
attraction. The estimated uncertainty is several months, and the
comet might have broken up even before discovery, although there
seems no hope for detecting the secondary nucleus on the available
1996 images, which range from May 10 to July 18. Predicted
separation distances and position angles for companion A relative
to primary B: 1997 May 12, 83", 253 deg; June 1, 88", 258 deg;
June 21, 94", 262 deg; July 11, 101", 266 deg."
(C) Copyright 1997 CBAT
1997 May 15 (6662) Daniel W. E. Green
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