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GCN Circular 1440

Subject
The Probable Host Galaxy of GRB/XRF 020427
Date
2002-06-25T06:01:45Z (22 years ago)
From
Andrew S. Fruchter at STScI <fruchter@stsci.edu>
A. Fruchter, J. Rhoads, I. Burud, A. Levan (STScI), S. Patel, C.
Kouveliotou (MSFC), Javier Gorosabel (IAA-CSIC, Granada), J. Hjorth
(Copenhagen U.)  report for the larger GOSH (Grb Optical Studies with
HST) Collaboration:

The field of XRF/GRB 020427 (Zand et al., GCN 1383) was observed with
HST on 10 June 2002 using the STIS CCD camera in open mode (50ccd).
The HST image was aligned to the USNO coordinate system using a
wide-field image obtained by the Danish 1.5m telescope at La Silla on
11 May 2002.  The position obtained by Fox et al. (GCN 1387, 1392) was
then located on the HST image.

We believe the combined error in the position of the X-ray transient
and the transfer to the HST image is less than 0."45, one-sigma.   The
XRF appears to lie on a galaxy with V magnitude of ~24.7.  This galaxy,
which is extended in the NE-SW direction with a total length of ~1."5,
has two neighbors within a few arseconds of similar magnitude and
morphology, as well as a number of fainter neighbors.   The position
obtained by Fox et al. places the GRB preferentially towards an end of
the galaxy.  If we use only the header of the Chandra image to do the
alignment, we find a location near a bright knot on the apparent host,
about one-sigma from the Fox position.   Images taken at a later date
could allow a search for an optical counterpart.

Observations of this field have also been undertaken independently at
the VLT (see the accompanying GCN 1439, Castro-Tirado et al.).  The VLT
observations show the complex of the three similar galaxies to be blue,
which is consistent with observations of GRB hosts in general (Fruchter
et al., Ap J. 519L, 13, 1999).

Images of the field are available at

http://www.stsci.edu/~fruchter/GRB/020427
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