[vsnet-grb-info 3387] GRB 060605: ROTSE-III Optical Counterpart

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5222
SUBJECT: GRB 060605: ROTSE-III Optical Counterpart 
DATE:    06/06/05 20:04:25 GMT
FROM:    Brad Schaefer at LSU  <schaefer at grb.phys.lsu.edu>

B. E. Schaefer (Louisiana State), E.S. Rykoff (U Mich), D.A. Smith 
(Guilford), R. Quimby (U Texas), report on behalf of the ROTSE 
collaboration:

ROTSE-IIIa, located at Siding Spring Observatory, Australia, found a
bright optical transient (Rykoff et al. 2006, GCN 5220) near the center of
the Swift BAT position for GRB 060605A (M. J. Page et al. 2006, GCN 5221).  
The Swift XRT and UVOT later reported a fading counterpart at this same
position (Page et al.  2006, GCN 5221).  In the first ROTSE image (started
48.7 s after the burst) the source was fainter than 16.5 mag (calibrated
against USNO stars in the R-band).  The source rapidly brightened to
roughly 15.7 mag by 150 seconds, and after a short plateau has since been
fading fast.  Our light curve shows some apparently significant
fluctuations starting ~1400 seconds after the burst.  The decline after
1000 seconds roughly follows a power law with index of -0.8.

A jpeg image is available at 
http://www.rotse.net/images/gsb213630_3a011-020_key.jpg
The optical transient is indicated by the central yellow circle labelled 
as object 44, while the blue circles represent stars in the USNO B1.0 
catalog.

Continuing observations are in progress.