TITLE:   GCN CIRCULAR
NUMBER:  7298
SUBJECT: GRB 080210: Keck photometry
DATE:    08/02/13 00:12:19 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley@astro.berkeley.edu>

D. A. Perley, M. Modjaz, J. S. Bloom, D. Poznanski, A. Miller, and D. 
Kocevski (UC Berkeley) report:

On the night of 2008-02-12 (UT), we observed the field of GRB080210 
(Grupe et al., GCN 7281) using Keck I (+LRIS) for 600s (R) and 900s (g). 
  We detect the GRB afterglow at the position noted by Klotz et al. (GCN 
7280) and Grupe et al.

Calibrating relative to seven stars from the SDSS calibration table 
given in GCN 7282 (Cool et al.), we measure the following magnitudes (at 
UT = 15:32, 55.7 hours after the BAT trigger):

R = 24.03 +/- 0.06
g = 25.20 +/- 0.07

The quoted uncertainty is photometric only and does not include scatter 
in the field calibration relative to SDSS (which is significant.)

Compared to the photometry given by Updike et al. (GCN 7288) this 
suggests an unusually slow decay rate of alpha~0.85.  This may suggest 
the presence of an underlying host galaxy, but the source appears 
pointlike in our images and the redshift of z=2.1 (Jakobbson et al., GCN 
7286) would argue against a large host galaxy contribution.  The X-ray 
afterglow* also appears to be decaying slowly.

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* http://astro.berkeley.edu/~nat/swift/00302888/bat_xrt.jpg.