GCN Circular 733

M. Metzger, A. Fruchter, N. Masetti, E. Palazzi, E. Pian, S. Klose,
and B. Stecklum report for a larger HST GRB Collaboration:

The field of GRB 000418 was observed by the Hubble Space Telescope
using the STIS camera in open (50CCD) mode on UT 2000 June 4.17.  The
position of the transient with respect to the STIS image was made by
performing relative astrometry of early infrared images of the
transient from the Calar Alto 3.5m (GCN 645
Not found
 
 
) and optical images on Apr
20.9 UT from the Telescopio Nazionale Galileo 3.5m with deep late-time
images from Keck (GCN 669
Not found
 
 
).  The transient position on the Keck images
was then transformed to the STIS image.

Near the position of the transient, a compact galaxy with half-light
radius of 0.13 arcsec is detected with R = 23.9 +- 0.2 mag (where much
of the photometric uncertainty is due to the uncertain spectral energy
distribution of the galaxy).  The best fit position of the OT is
approx 0".08 +- 0".15 arcsec east of the center of this galaxy, which
we infer is the likely host.  The magnitude measured is within a few
tenths of a magnitude of the May 6 Keck measurement (GCN 669
Not found
 
 
), and
thus the OT does not likely contribute significant flux to the host in
the STIS image.

The next nearest galaxies to the transient is a pair approx 2 arcsec
southeast of the host and are detected in both the STIS and Keck
images at total R magnitude of 26.2 +- 0.3 mag.  The pair shows no
significant extension toward the host galaxy in either the STIS or
Keck images.

A reduced image of the STIS field, with transient location indicated, can
be obtained at http://www.stsci.edu/~fruchter/GRB/000418.

This message may be cited.