GCN Circular 1518
Subject
GRB 020813 : HST observations
Date
2002-08-22T17:04:55Z (22 years ago)
From
Andrew Levan at U.of Leicester <anl@star.le.ac.uk>
A.J. Levan, A.S. Fruchter, I. Burud and J.E. Rhoads (STScI)
report for the larger GOSH collaboration:
The field containing the optical counterpart of GRB 020813 was imaged by
HST using ACS/HRC, ACS/WFC and NICMOS on 17th August beginning at 04:00 UT
approximately 98 hours after the burst.
The optical counterpart is clearly visible in our images. Using the
zeropoints for the filters on ACS/WFC, as given below, we find the
magnitude of the counterpart to be:
FILTER Z_P(AB) OT MAG(AB)
==========================
F435W 25.47 23.20
F606W 26.35 22.71
F814W 25.86 22.33
This is consistent with a spectral slope of beta =-0.8.
Comparing to early, 3 hour I Band observations (GCN 1513) gives
an approximate slope of ~t^-1.07. Comparing to observations taken after
23 hours (also GCN 1513) indicates a somewhat faster (broken) slope
of t^-1.35.
The OT appears largely point like, however a PSF subtraction reveals some
evidence for a possible 25th magnitude host galaxy underlying the OT.
Images of the field of GRB 020813 may be found at
http://www.stsci.edu/~fruchter/GRB/020813
Analysis is continuing and further observations are planned.