GCN Circular 7870
Subject
GRB 080603A: Late-time Keck imaging and spectroscopy
Date
2008-06-13T00:28:58Z (16 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
D. A. Perley, J. S. Bloom, A. A. Miller, J. Shiode, J. Brewer, D. Starr,
and R. Kennedy (UC Berkeley) report:
On the night of 2008-06-07 (UT) we re-observed the location of GRB
080603A (GCN 7790, Paizis et al.) with Keck I / LRIS in g and R filters
for 785s and 690s respectively, starting at 12:30 UT. The optical
afterglow (Gomboc et al., GCN 7788; Chornock et al., GCN 7789) is
well-detected as the northern member of a complex of sources.
Calibrating relative to four nearby USNO B1.0 stars we estimate an
afterglow magnitude of
R = 23.7 +/- 0.1 (t = 4.05 days)
The extended source reported by Rymyantsev et al. (GCN 7860) is clearly
detected and is well-resolved into the afterglow plus two extended
sources in the g-band frame, with the southern source significantly
redder than the afterglow and the faint western source.
A color image of the field is posted to:
http://lyra.berkeley.edu/~dperley/080603a/080603a_color.png
Given the very strong absorption lines reported in our spectroscopic
observations (Perley et al., GCN 7791), this complex may be a bright
host galaxy of this burst, as suggested by Rumyantsev et al. However,
the sources above are offset significantly from the afterglow (which
itself is not obviously extended), suggesting instead that they may
represent one or both of the intervening absorbers.
Later the same night, we acquired 2x900s spectra using a slit covering
the northern (afterglow) source and southern source, and an additional
1x600 spectrum using a slit covering the faint western source and the
bright, clearly separated eastern source noted by Kann et al. (GCN
7822). No obvious emission lines are evident in any spectrum. At any
of the host and absorber redshifts of z=1.688, z=1.563 and z=1.271
respectively, the bright potential emission features (Ly-alpha, OII) are
expected to fall outside our wavelength coverage, on top of sky lines,
or be strongly attenuated by the atmosphere, so this result is mildly
supportive of an association of these sources with the host and/or
absorbers. However, the integrations were relatively short, and further
follow-up is warranted.