GCN Circular 6843
Subject
GRB 071003: Keck HIRES spectroscopy
Date
2007-10-03T23:12:24Z (17 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
D. A. Perley (UCB), J. X. Prochaska (UCSC), J. S. Bloom (UCB), and G.
Smith (UCO/Lick) report on behalf of the GRAASP collaboration:
We observed GRB 071003 (Schady et al., GCN 6837) with Keck/HIRESr
starting at UT 10:24 for one exposure of 1700s. The data were acquired
through very high airmass and have a low S/N ratio (~1 per 1.3 km/s
pixel at 5000A).
We identify no obvious absorption features in either the 2D image nor 1D
spectrum. Allowing for the following priors, we place the following
upper limits on the GRB redshift:
1. Assuming the GRB host galaxy would emit no flux below the Lyman
limit, we infer z_GRB < 3.4
2. Assuming the GRB host galaxy would imprint a damped Lya profile on
the spectrum, we infer z_GRB < 2.5
3. Assuming the GRB host galaxy would imprint a strong MgII absorber on
the spectrum (EW > 1A), we infer z_GRB < 1.
Given these constraints and the U-band detection from Mishra et al. (GCN
6840), it is possible that this GRB is at low redshift. We encourage
follow-up observations to search for, or place limits on, a low-redshift
host galaxy or associated supernova.