[vsnet-grb-info 389] GRB020322 : HST/STIS observations

[GCN Circulars <gcncirc@lheawww.gsfc.nasa.gov>]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1536
SUBJECT: GRB020322 : HST/STIS observations 
DATE:    02/09/05 23:20:39 GMT
FROM:    Andrew Levan at U.of Leicester  <anl@star.le.ac.uk>

I. Burud, A. Fruchter, J. Rhoads, and A. Levan (STScI) report for the
larger GOSH (GRB Optical Studies with HST) collaboration:

We observed the field of GRB 020322 with STIS in open (50CCD) mode on
UT 2002 April 8 and on June 5.  The position of the
transient with respect to the STIS image was determined by performing
relative astrometry using the optical image of the transient from
Bloom et al.  (GCN 1296).  The accuracy of the position translated
to the HST image is estimated to be 0.08 arcsec.

We see no evident OT, but at the position of the transient there is
an extended 27th magnitude galaxy which is likely to be the host.
The sum of the two epochs of observations is displayed at

http://www.stsci.edu/~fruchter/GRB/020322

When subtracting the images from the two epochs no residual signal is
detected above 3 sigma near the position of the OT, giving a limiting
magnitude of 30.1 mags for any transient.

Based on the ground-based observations from Bloom et al. (GCN 1294),
Greiner et al. (GCN 1298), Hjorth et al. (GCN 1300) and Williams et
al. (GCN 1307) and the non-detection of the OT in the HST/STIS image
we conclude that the late time R-band decay of the OT must be steeper
than 2.0. A plot of all the data points can be found on the aforementioned
web page.

We thank J. Bloom and the Caltech GRB group for making their ground-based
data rapidly public (GCN1296).

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