J.X. Prochaska (UCO/Lick Observatory), H.W. Chen (MIT),
K. Hurley (UCB), J.S. Bloom (Harvard/CfA), J.R. Graham (UCB),
and W.D. Vacca (NASA/Ames) report:
Using SCAM with the NIRSPEC instrument on the KeckII telescope,
we imaged the ~50"x50" region surrounding GRB031203 (Gotz et al., GCN 2459).
We acquired exposures in the N3 (~J; 540s), N5 (~H; 360s), and
K' (540s) bands with approximately 0.5" seeing in photometric conditions.
Within the 6" XMM error circle, we identify 2 objects:
(1) A point source at RA=08:02:29 DEC=-39:51:09 (ANDICAM 1)
(2) A galaxy at RA=08:02:29 DEC=-39:51:12
The latter object nearly coincides with the VLA position of the radio
source in the XMM error box (Frail, priv. communication).
We believe the GRB event occurred within this galaxy.
The observed K'-band magnitude of the galaxy is 16.5 +/- 0.05
Adopting an extinction E(B-V)=0.97, we estimate a corrected
K'-band luminosity K'=16.15 mag. The galaxy also has an
ellipticity E=0.23 and PA=-8 deg.
Finally, adopting K'(M*) = -23.3 from the 2MASS survey (Bell et al. 2003),
we note an M* galaxy at z=0.17 would have K'=16.15 assuming an LCDM
cosmology and no evolution in the stellar population.
We also identify a ~5sigma object 1.4"N and 0.2E" of the galaxy center
with observed K' magnitude of 21.1 +/- 0.2. This tentative detection
lies within 0.5" of the VLA position.
No object was observed in our images at the position of
the REM source (Zerbi et al., GCN 2466) to K'<21.5 mag.
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