TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3488
SUBJECT: GRB 050525a: MDM Observations
DATE:    05/05/26 15:35:49 GMT
FROM:    Nestor Mirabal at U Michigan  <mirabal@umich.edu>

N. Mirabal (U. Michigan), D. Bonfield and K. Schawinski (U. Oxford),
report on behalf of the MDM GRB follow-up team:

"Continuous r'-band photometry of the GRB 050525a afterglow (Rykoff et al.
GCN #3465) was obtained with the RETROCAM imager (Morgan et al.,
astro-ph/0502274) installed on the MDM 2.4m telescope. The data consists
of ~120 points spanning from 4.4 hr to 11.6 hr after the burst. During
this period, the magnitude of the optical afterglow is seen to decline
from R ~ 18.5 to R ~ 19.6, referenced to the R ~ 17.2 USNO star listed
by Rykoff et al. (GCN #3465). A fit to the latter part of the observations
yields a power-law decay slope of -1.38 +/- 0.2, consistent with a
tentative steepening of the decay after ~0.4 days. Further analysis is in
progress.

A graph of the preliminary differential magnitude light curve is available at

http://www-personal.umich.edu/~mirabal/grb050525/lightc.ps"