GCN Circular 872

A. Fruchter, (STScI), P. Vreeswijk (Amsterdam), V. Sokolov (SAO RAS)
and A. Casto-Tirado (IAA-Granada, INTA-Madrid) report on behalf of the 
larger HST GRB collaboration report:

We observed the field of GRB 991208 with the HST STIS CCD on August 3,
2000, or approximately 8 months after outburst.  A total exposure time
of 5210s was obtained in the (50CCD) clear aperture.  At the position
of the burst we find a very compact galaxy with a magnitude of V= 24.6
+/- 0.15, where a conservative error bar is given due to the very wide
bandpass of the filter.  The full-width at half-maximum (FWHM) of the
galaxy is measured as 0."095, only marginally larger than the intrinsic
0."08 of the STIS PSF.  However, both curve-of-growth analysis and
direct subtaction of a STIS PSF indicate that the object is indeed
resolved.  We estimate the intrinsic FWMH of the core of the galaxy is
less than 0."06.

Comparison of the HST image with ground-based images (Castro-Tirado et
al., A&A submitted, see also GCN 452
Not found
 
 
) shows the position of the optical
transient to be offset from the center of the host by less than the
0."1 one-sigma uncertainty in the relative positions.

We believe the ellipticity and position angle reported for the host by
Bloom et al. (GCN 764
Not found
 
 
) is due to the presence of a fainter, small
object located approximagely 1" to the ESE of the host.  It is not clear
from the HST image whether these two objects are merely close due to a
projection effect or whether they are indeed physically related.

The wider (50") field of the STIS CCD shows a rich association of
spiral galaxies surrounding the position of the OT.  While some of the
spirals show grand design or prominent bulges, and are up to 5" across,
we cannot rule out the possibility that the host of the GRB (which is
at a redshift of 0.7, Dodonov et al., GCN 475
Not found
 
 
) is a member of this
apparent group of galaxies.

The images can be seen at http://www.stsci.edu/~fruchter/GRB/991208 .

This GCN may be cited.