[AAVSO-HEN] GRB 080507: Keck photometry

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  7706
SUBJECT: GRB 080507: Keck photometry
DATE:    08/05/10 02:33:56 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley at astro.berkeley.edu>

D. A. Perley (UC Berkeley), J. X. Prochaska (UCO/Lick), and J. Hennawi 
(UCB) report:

We imaged the field of Super-AGILE GRB 080507 (Lapshov et al., GCN 7697) 
with Keck I (+LRIS) during morning twilight starting at 15:03 UT on 
2008-05-08 (31.3 hours after the trigger).  Four exposures were taken in 
g and R filters simultaneously, although due to twilight only the first 
two R-band frames were usable.

We detect the optical afterglow reported by Kann et al. (GCN 7701) at a 
position of:

RA  =  15:34:43.39
Dec = +56:26:08.28
(estimated uncertainty of 0.7")

in R-band.  Our magnitude, calibrated to seven USNO-B1.0 stars, is R = 
22.20 +/- 0.11 at 1.31 days after the trigger.  This supports the 
generally non-fading behavior between 1-2 days after burst in 
observations from the Swift UVOT (Breeveld et al., GCN 7702) and 
Tautenberg (Kann et al.).

For reference, the observed magnitudes of two nearby USNO stars in the 
same calibration system are:

15:35:10.99 +56:23:57.02  R = 20.53 +/- 0.02
15:34:47.68 +56:25:16.44  R = 18.63 +/- 0.01