Circular No. 6619
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)
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Phone 617-495-7244/7440/7444 (for emergency use only)

GRB 970228
     B. Soifer, G. Neugebauer, L. Armus, M. Metzger, S. Kulkarni,
S. Djorgovski, and C. Steidel, California Institute of Technology;
and D. Frail, National Radio Astronomy Observatory, communicate:
"Near-infrared images of the region near the optical variable
reported by Groot et al. (IAUC 6584) were obtained on Mar. 30 and
31 UT with the Keck I 10-m telescope (+ NIRC).  A source is
detected in both bands J and K within 0".3 of the extended source
reported by Groot et al. and Metzger et al. (IAUC 6588).  Within a
1".2 aperture, the source has J = 23.5 +/- 0.2 (combined data from
Mar. 30.3 and 31.2), and K = 22.0 +/- 0.2 (Mar. 30.2).  This
corresponds to a region including the point source detected by HST
(IAUC 6606).  A comparison with the Mar. 17.8 J magnitude reported
on IAUC 6611 indicates that the near-infrared brightness of the
region has strongly varied over the interval."
     K. Sahu, M. Livio, L. Petro, and F. D. Macchetto, Space
Telescope Science Institute; J. van Paradijs, University of
Amsterdam; and C. Kouveliotou, G. Fishman, and and C. Meegan,
Marshall Space Flight Center, NASA, communicate:  "GRB 970228 was
observed again with the HST Wide Field and Planetary Camera (WFPC2)
between Apr. 7.15 and 7.32 UT, about 38 days after the outburst.
The optical transient (IAUC 6584, 6588, 6606) was placed at the
center of the Planetary Camera field-of-view.  Observations were
taken in the F606W (wide V) and F814W (I) filters.  Four exposures
with a total integration time of 4700 s were taken in the F606W
filter and two exposures with a total integration time of 2400 s
were taken in the F814W filter.  The optical counterpart, as well
as the extended source, were clearly detected in both passbands.
The derived magnitudes for the point source are 26.0 +/- 0.3 and
24.6 +/- 0.3 in the F606W and F814W filters, respectively.  The
data were put in the HST archive on the day of the observations.
The data can be accessed through the World Wide Web at
http://archive.stsci.edu/."


TIME ADJUSTMENT ON 1997 JUNE 30
     Bulletin C13 of the International Earth Rotation Service
announces that a positive leap second will be introduced such that
the sequence of UTC second markers will be: 1997 June 30d23h59m59s,
30d23h59m60s, July 1d00h00m00s.  Beginning 1997 July 1, the
difference UTC-TAI = -31s.

                      (C) Copyright 1997 CBAT
1997 April 9                   (6619)            Daniel W. E. Green