GCN Circular 778

HST/STIS observations of the host galaxy of GRB 980329

Stephen Holland, Bjarne Thomsen (University of Aarhus),
Jens Hjorth, Johan Fynbo (University of Copenhagen),
Michael Andersen (University of Oulu),
Gunnlaugur Bjornsson (University of Iceland),
Andreas Jaunsen (ESO),
Priya Natarajan (University of Cambridge, & Yale), and
Nial Tanvir (University of Hertfordshire)

     We have used the Space Telescope Imaging Spectrograph (STIS) on
the Hubble Space Telescope to image the host galaxy of GRB 980329.  We
obtained 8072 seconds of STIS/CCD images with the 50CCD (clear)
aperture and 5416 seconds with the F28X50LP (long pass) aperture.
This data was taken as part of the Survey of the Host Galaxies of
Gamma-Ray Bursts (Holland et al., GCN 698
Not found
 
 
) approximately 880 days
after the burst occurred.  Combined images are now available at
"http://www.ifa.au.dk/~hst/grb_hosts/data/index.html".  The drizzled
F28X50LP image is based on two orbits worth of data, and will be
updated when the data from the third orbit is available.

       A preliminary determination of the location of the radio
transient VLA J070238.0+385044 associated with GRB 980329 (Taylor et
al. 1998, ApJL, 502, L115), based on the astrometry of three USNO-A2.0
stars, is (X,Y) = (1039,1027) where the three-sigma uncertainty in the
astrometric solution is 20 drizzled STIS pixels (0.5 arcsec).  There
is a faint, extended object at (X,Y) = (1031,999) in our drizzled
50CCD image.  This object is also visible in the F28X50LP image.  The
object is approximately three sigma southwest of the position of the
GRB, and is the best candidate for the host galaxy of GRB 980329.  An
image showing the location of the galaxy and the GRB is available at
"http://www.ifa.au.dk/~hst/grb_hosts/data/grb980329cd.gif".  The
probable host galaxy has AB magnitudes, in an aperture of radius 0.25
arcsec, of CL = 28.6 +/- 0.3 and LP = 28.1 +/- 0.3.  If we assume that
the galaxy has a power-law spectrum then the preliminary Kron-Cousins
R-band magnitude is R = 27.7 +/- 0.3.  We also derived a preliminary
calibration based on two stars from Rhoads et al. (GCN 157
Not found
 
 
) and found
R = 28.2 +/- 0.3.  These results are consistent with each other, and
are consistent with the host magnitude being 26.8 < R < 29, as
determined by Gorosabel et al. (1999, A&A, 347, L31) from the decay of
the optical light curve.  The faintness of the galaxy is consistent
with it having a redshift of z > 2 (Fruchter 1999, ApJ 512, L1; Lamb
et al. 1999, A&AS, 138, 479), although we can not rule out z < 2 from
the HST/STIS data alone.