GCN Circular 4364

J. S. Bloom (UC Berkeley), on behalf of a larger collaboration, reports:

"We began observations of the bright short burst GRB 051221 (Parsons  
GCN #4363) with the PAIRITEL 1.3m at 2005-12-21 02:54:02 UTC, about  
30 minute after the GCN circular and 1hr3min after the GRB. In a  
stack of the first 313sec, we detect no new sources to at least the  
2MASS limit in JHKs bands. A visual comparison with the DSS-2 (F- 
plate) shows that most of the sources fainter than 2MASS in the  
PAIRITEL mosaics have optical counterparts.  Some of the faintest IR  
sources do not have detected counterparts but this is likely due to  
the redness/faintness of the sources. In particular, we point out  
objects at J2000:

    A: 21:54:57.84 +16:53:07.5   (inside the error circle)
    B: 21:55:00.89 +16:56:50.2   (red, outside the error circle)
    C: 21:55:01.58 +16:57:07.1   (red, outside the error circle,  
extended)

Further analysis is ongoing but we suggest that these sources be  
monitored for variability, especially object A."

A RGB (=KsHJ) finding chart may be found at:
  http://astro.berkeley.edu/~jbloom/grb051221.ps

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