GCN Circular 749

GRB981226, HST/STIS observations of the host galaxy

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

     We have obtained 7865 seconds of HST/STIS images with the 50CCD
(clear) aperture and 7909.63 seconds of HST/STIS images with the
F28X50LP (long pass) aperture of the host galaxy of GRB 981226.  These
data was taken as part of the Survey of the Host Galaxies of Gamma-Ray
Bursts (Holland et al. GCN 698
Not found
 
 
) approximately 555 (clear) and 558
(long pass) days after the burst.  Combined (drizzled) images are now
available at "http://www.ifa.au.dk/~hst/grb_hosts/data/index.html".

     The galaxy identified by Frail et al. (1999, ApJL, 525, L81) is
the only object within the error circle of the radio transient (VLT
J232937.2-235553) associated with GRB 981226.  This galaxy is located
at (X,Y) = (1033,1056) on the drizzled STIS clear image, has an
ellipticity of approximately 0.65, and its major axis has a position
angle of approximately -75 degrees east of north.  We measured the
following AB magnitudes for this galaxy using an aperture with a 1.1
arcsecond radius: CL = 25.04 +/- 0.07 in the STIS clear aperture and
LP = 24.50 +/- 0.10 in the STIS long pass aperture.  We used the
photometry of Walker (1994, PASP, 106, 828) to calibrate our data (see
Holland et al. 2000, in preparation, for details) and found V-R = 0.50
+/- 0.14, V = 24.80 +/- 0.08, and R = 24.30 +/- 0.11 in the Johnson
and Kron-Cousins systems.  We note that the northeast side of the
galaxy is significantly bluer than the rest of the galaxy (see
"http://www.ifa.au.dk/~hst/grb_hosts/data/grb981226_colour.gif").  We
estimate that the blue structure on the north side of the galaxy has
V-R = 0.1 and the south edge of the galaxy has V-R = 1.5.  There is a
compact source at each end of the blue structure.  The west source
corresponds to the photometric centre of the galaxy.

     Frail et al. (1999) found that the galaxy was located 0.55 +/-
0.53 arcseconds west and 0.41 +/- 0.43 arcseconds south of the radio
afterglow.  This error ellipse encompasses the eastern half of the
galaxy and the eastern compact source in the blue structure.

     We also note the presence of a faint point source (V ~= 28.4,
V-R ~= 0.3), at (X,Y) = (1015,1064) in the drizzled STIS clear image,
approximately 1.0 arcseconds from the nominal position of the radio
afterglow.