Central Bureau for Astronomical Telegrams
IAUC 6582: GRB 970228
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Circular No. 6582
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)
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GRB 970228
A. Guarnieri, C. Bartolini, A. Piccioni and N. Masetti,
University of Bologna; E. Costa, IAS, Frascati; F. Frontera, ITESRE
and University of Ferrara; and E. Palazzi, ITESRE, Bologna, write:
"A preliminary analysis of CCD observations of the GRB 970228 field
(IAUC 6572), obtained with the Bologna University 1.5-m telescope
in B and R bands (limiting mag about 22 for both) on Feb. 28.76,
Mar. 1.81, 3.76, 4.82, and 5.86 UT, shows no object fading by > 0.2
mag. A comparison between these frames and the Digital Sky Survey
(DSS) shows that all of the objects brighter than B about 19 and R
about 20 in our frames are also present in the DSS field and that
their luminosities have not noticeably changed since then (1950.294)."
J. S. Bloom, N. Tanvir, and R. A. M. J. Wijers, Institute of
Astronomy, Cambridge, report: "We have obtained BVR images of the
error box of GRB 970228 using the 2.5-m Isaac Newton Telescope (La
Palma) on Mar. 8 and 9. On Mar. 9.89 UT (seeing < 1"), we resolve
the galaxy coincident with the radio-source position (Frail et al.,
IAUC 6576) just outside the GRB error box (Hurley et al., IAUC 6578).
We find V = 21.4, R = 21.2, B = 24.1. In the 0.7-arcmin**2 region
of overlap between the GRB error box and the error region of the
MECS/LECS x-ray source (Costa et al., IAUC 6578), we find about 30
objects down to B = 24.5 or R = 24. Three of the fifteen objects
with R < 22 are galaxies (based on their morphology) whose R.A.
and Decl. end figures (equinox 2000.0), along with magnitudes (given
as R, V-R, and B-V), are as follows: 46s.14, 46'45".9, 21.6, +0.7,
+0.9; 46s.68, 46'17".0, 20.0, +1.3, +1.1; 45s.41, 45'49".9, 20.0,
+0.9, +1.7. We suspect that an object at 46s.52, 47'25".7, 20.6,
+1.4, +1.2 may also be a galaxy."
M. R. Metzger, S. R. Kulkarni, S. G. Djorgovski, R. Gal, and
C. C. Steidel, California Institute of Technology; and D. A. Frail,
National Radio Astronomy Observatory, communicate: "Images of the
optical counterpart (Margon et al., IAUC 6577) to the radio source
detected by Frail et al. (IAUC 6576) were obtained with the Keck II
10-m telescope on Mar. 6.32 UT and with the Palomar 1.5-m reflector
on Mar. 6.19, revealing an extended source of R = 20.8 with center
at R.A. = 5h01m41s.67, Decl. = +11o47'04".8 +/- 0".2 (equinox
2000.0). This source lies in the error circle of the x-ray source
seen by Costa et al. (IAUC 6576) and near the error box of GRB
970228 (IAUC 6572, 6578). A spectrum taken with Keck II on Mar.
9.25 shows a galaxy at redshift 0.498, inferred from Ca II
absorption and narrow [O II] 372.8-nm and [O III] 500.7-nm emission
features."
(C) Copyright 1997 CBAT
1997 March 11 (6582) Daniel W. E. Green
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