[vsnet-grb-info 7130] GRB 081221: Probable host galaxy in Keck imaging

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8711
SUBJECT: GRB 081221: Probable host galaxy in Keck imaging
DATE:    08/12/23 11:23:47 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley at astro.berkeley.edu>

D. A. Perley, J. S. Bloom (UC Berkeley), J. Kalirai (STSCI), R. 
Strickler, E. Ramirez-Ruiz (UCSC), and A. A. Miller (UCB) report:

We began a series of deep optical imaging exposures on the field of GRB 
081221 (Hoversten et al., GCN 8687) using the Keck I telescope (+LRIS) 
starting at 2008-12-23 at 5:06 UT.  We acquired 10x330s in g-band and 
10x300s in I-band (simultaneously using the 560 dichroic).

A extended source coincident with the Gemini (Tanvir et al., GCN 8698) 
and Swift XRT (GCN 8690) afterglow positions is clearly detected in our 
g-band stack, which we tentatively identify as the host galaxy.  The 
magnitude within a 1.0" aperture of this object is approximately B~25.4 
(calibrated relative to the USNO star at RA=15.797098, dec=-24.412259, 
B2=19.59).  It is only marginally detected in the I-band imaging, with 
an estimated magnitude of I~24.5, though photometry in this band is 
complicated by blending with a nearby object.

The detection of a host galaxy would be consistent with a low-redshift 
origin (GCN 8698).  Within the significant uncertainties of the 
photometric calibration the color of the galaxy appears typical of 
normal GRB hosts.  Further analysis is planned.

An image of the field is posted to:
http://lyra.berkeley.edu/~dperley/081221/081221hostkeck.png