TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  756
SUBJECT: GRB 990510 Host Galaxy Discovery
DATE:    00/07/30 00:32:12 GMT
FROM:    Josh Bloom at CIT  <jsb@astro.caltech.edu>

GRB 990510 Host Galaxy Discovery

J. S. Bloom, on behalf of the larger Caltech-NRAO-CARA GRB
Collaboration, reports:

"We have discovered a faint extended source nearly coincident with the
position of GRB 990510. This source, which we identify as the host galaxy
of GRB 990510, is visible in new HST/STIS imaging taken on 29 April 2000
as part of the HST proposal #8189 (see Fruchter et al. GCN #386) and made
public on 28 July 2000. The total integration time is 5840 s taken in 8
individual exposures. Registration of the early epoch (17 June 1999) where
the OT was bright reveals the OT occurred (0.064" +/- 0.009") West
and (0.015" +/- 0.012") North of the center of the host
galaxy.  This amounts to a significant displacement of (66 +/- 9) mas or
~600 pc at a distance of z=1.62 (Galama et al. 1999), though the OT does
appear to reside within the detectable light of the galaxy.  The galaxy
extension is PA=80.5 +/- 1.5 deg with an ellipticity of about ~0.5.  
Preliminary magnitude estimates reveal that V_host = 28.5 +/- 0.5 mag
(referenced to star C of Beuermann et al. 1999).  The host does appear to
be marginally detected in the July 1999 imaging as well (although see GCN
#386)."

An image of the field from both epochs as well as a close-up of the
host and the 3-sigma location of the GRB can be found at:
   http://astro.caltech.edu/~jsb/grb990510-host.ps

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