Subject: IAUC 6735: GRB 970828; USNO 1425.09823278; C/1996 J1
From: quai@cbatmpc (IAUC mailing list)

Circular No. 6735
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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GRB 970828
     K. Z. Stanek, M. R. Garcia, and M. Krockenberger, Harvard-
Smithsonian Center for Astrophysics, communicate:  "Analysis of
images centered on the error box of the x-ray counterpart to GRB
970828 detected by RXTE (IAUC 6726, 6728) reveals no significantly-
variable objects to a magnitude limit of R = 22.  The variability
for the 460 point sources in the field with 15.5 < R < 22 is rms <
0.3 mag.  The field contains numerous well-resolved galaxies.  The
images were obtained with the 1.2-m telescope of the F. L. Whipple
Observatory on Aug. 30.18, 30.19, Sept. 2.26, 2.27, 3.23, 3.24,
4.12, and 4.14 UT in the Cousins R filter (15-min exposures).  The
images cover an area 11' x 11' and are available as FITS files by
anonymous ftp at cfa-ftp.harvard.edu, in pub/kstanek/GRB970828, or
through the WWW at http://cfa-www.harvard.edu/~kstanek/.  The faint
(R = 24.5 +/- 0.5) optical object coincident with the variable
radio source (IAUC 6730) is undetected on all of our individual and
daily-summed images, which reach a detection threshold of R about
22.  Note that the position of this radio source is outside the 30"
revised ASCA error radius (IAUC 6732)."

                      (C) Copyright 1997 CBAT
1997 September 5               (6735)            Daniel W. E. Green