Central Bureau for Astronomical Telegrams
IAUC 6663: GRB 970508
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Circular No. 6663
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)
GRB 970508
I. A. Smith, Rice University; and R. A. Gruendl, University of
Illinois at Urbana/Champaign report, on behalf of the Berkeley-
Illinois-Maryland Association (BIMA) GRB team: "Using the BIMA
array at 3.5 mm, we mapped most of the 5' gamma-ray-burst error box
reported on IAUC 6649 for 5.5 hr, starting May 10.1 UT. This
region includes the new x-ray source SAX J0653.8+7916 (IAUC 6656).
No obvious sources were detected, with a 1-sigma rms of 10 mJy. A
deeper stare of SAX J0653.8+7916 was performed between May 10.8 and
11.1, although 2 hr were lost because of storms. No sources were
detected, with a 1-sigma rms of 2.0 mJy. In another stare between
May 15.1 and 15.3, there may be a mm-continuum source at the
location of the radio variable reported on IAUC 6662, though our
preliminary analysis gives a flux of 5.5 +/- 1.7 mJy, which is only
marginally significant."
C. Chevalier and S. A. Ilovaisky, Observatoire de Haute-
Provence, report that three 15-min CCD exposures of Bond's variable
object (IAUC 6654), obtained with the 1.2-m Haute-Provence telescope
(+ Cousins R filter) on May 14.40 UT under nonphotometric conditions,
shows that it has further decreased in brightness, to R = 21.1 +/-
0.2 (using as comparison the magnitude given by Schaefer et al. on
IAUC 6658 for the brighter star located 13" to the north).
A. I. Kopylov, V. V. Sokolov, and S. V. Zharikov, Special
Astrophysical Observatory, Russian Academy of Sciences; and M.
Feroci, E. Palazzi, and the rest of the BeppoSAX GRBM team, report:
"Optical multicolor observations of Bond's variable object (IAUC
6654) were obtained with 1-m (May 9.89 UT) and 6-m telescopes. Our
preliminary reduction shows the following Johnson and Kron-Cousins
magnitudes: May 9.89, R_c = 21.1; May 10.77, B = 20.90, V = 20.34,
R_c = 19.87, I_c = 19.43; 10.93, 20.79, 20.33, 19.92, 19.30; 11.76,
21.42, 20.77, 20.18, 19.48; 12.87, 21.70, 21.19, 20.77, 20.25;
13.88, 21.93, 21.33, 21.01, 21.01. Estimated errors are about 0.15
for the 1-m telescope measurements and 0.05-0.08 for the others.
These measurements of the 'broadband spectrum' roughly correspond to
a power law with a spectral index of -1.5 for May 10 and 12, and
-2.2 for May 11. During a 1-hr interval on May 13, the object
showed variability of about 0.2 mag both in the B and V bands,
though only one exposure was obtained in the I_c band. The unusual
'Z-shaped' object (IAUC 6658) is resolved into two components in the
May 13 R_c image (FWHM seeing = 1".6): a very red point source (R_c
= 21.7) adjacent southward to an arc-like extended source of size
5".5 from tip to tip and 2"-2".5 in width. The brightness of the
extended source increases from the middle to the tips."
(C) Copyright 1997 CBAT
1997 May 16 (6663) Daniel W. E. Green
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