[vsnet-grb-info 5145] GRB 071003: Possible rebrightening

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6847
SUBJECT: GRB 071003: Possible rebrightening
DATE:    07/10/04 08:33:56 GMT
FROM:    Daniel Perley at U.C. Berkeley  <dperley at astro.berkeley.edu>

D. A. Perley, W. Li, J. S. Bloom (UC Berkeley), C. Fassnacht (UC Davis), 
and P. Nugent (LBL) report:

On the night of 2007-10-04 (UT) we imaged the field of GRB 071003 with 
Keck I + LRIS, in g+R filters simultaneously for 3 exposures of 300 
seconds, starting at 04:49 UT.

We detect at the position reported by Li (GCN 6838) a bright source with 
an estimated magnitude of R~20, though photometry is complicated by the 
presence of the nearby 11th magnitude star.  The position is consistent 
within 0.3" of the KAIT detection, strongly suggesting that this is the 
same source.  Given the rapid fading noted in earlier circulars (GCN 
6841, GCN 6844) and the limit of R > 21 reported by Shih et al. (GCN 
6848) this may suggest that the optical afterglow is rebrightening, 
either due to a late-time flare or a rising low-redshift supernova.

We also note what appears to be a faint, extended object approximately 
2" to the southwest of the afterglow (towards the bright star), which 
may be the host galaxy of this burst.

Further analysis is in progress.  Additional observations are strongly 
encouraged to further examine the nature of this transient.