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GCN Circular 1761

Subject
XRF 020903 : HST observations
Date
2002-12-17T18:59:13Z (21 years ago)
From
Andrew Levan at U.of Leicester <anl@star.le.ac.uk>
Andrew Levan (U. Leicester/STScI), Andrew Fruchter, Lou Strolger, Ingunn
Burud and James Rhoads (STScI) report for the GOSH collaboration.

The candidate optical transient for XRF 020903 (Soderberg et al, GCN 1554)
was imaged with HST/ACS in F606W on 3rd Dec 2002. 4 dithered exposures
were obtained with a total exposure time of 1840s.

The candidate appears to be within an irregular galaxy, with four
(possibly interacting) components. Astrometry with images obtained
with the CTIO 4-m telescope and Mosaic imager on Sept 4th and 9th 2002
(Fruchter et al, GCN 1558) shows that the transient source is located at
a position coincident with the peak of the most western of these compact
knots (with a positional accuracy of approximately ~0."1). The knot has
an F606W AB magnitude of 22.6 and a FWHM of ~0."14, greater than the PSF
of ACS. Hence the source is resolved at this resolution, indicating that
an AGN does not dominate the optical light from this object.

The galaxy, named G2 by Soderberg et al, (GCN 1554) is clearly an
interacting system. However, as noted by Soderberg et al the redshift
difference (z=0.23 for G2 and z=0.25 for the host of the candidate OT)
indicate that the systems are not associated.

Using a 1" aperture the magnitude of the entire system in F606W is
approximately R=21, roughly consistent with the late time magnitudes
determined by Gorosabel et al (GCN 1631).

Observations taken at a later date will allow a search for further
variability in this source.

Images of the host galaxy, and surrounding field can be found at

http://www.stsci.edu/~fruchter/GRB/020903
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