University of Michigan 
Columbia University Astronomy and 

MDM Observatory GRB Team

GRB 050525a Optical follow-up

MDM 2.4m RETROCAM - SDSS r' Filter
(J2000) 18h 32m 32s.58 +26° 20' 22.6" (2.2 x 2.2 arcmin)

GCN Circular #3488
GRB 050525a: MDM Observations
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 #3468). 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

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

The data in the following figure are preliminary, for internal use only.
They should not be reproduced without the permission of the authors.
GRB 050525a Decay Curve

Nestor Mirabal
Jules Halpern
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Last Modified: February 13, 2006