TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3363
SUBJECT: GRB 050502a: Optical Observations
DATE:    05/05/06 01:03:13 GMT
FROM:    Nestor Mirabal at U Michigan  <mirabal@umich.edu>

N. Mirabal (U. Michigan), M. Boettcher, J. Shields, M. Joshi (Ohio U.),
and J. P. Halpern (Columbia U.) report on behalf of the MDM GRB follow-up
team:

"We monitored the optical afterglow (Yost et al., GCN #3322) of GRB
050502a with the MDM 1.3m telescope beginning on 2005 May 2.163 UT and
spanning from 1.8 hr to 8.2 hr after the burst. Preliminary photometry
referenced to a USNO-B1.0 star at (J2000) R.A. 13:29:59.84, Decl.
+42:43:00.2 listed as R = 16.01, indicates that the OT faded from 
approximately R~19.3 on May 2.163 to R~21.4 on May 2.36, and continued to 
decline until the end of the monitoring period.  The corresponding 
power-law decay index is -1.44 +/- 0.2. This is steeper than the decay 
index of -1.03 estimated from the earlier observations of Yost et al. 
(GCN #3322)."