University of Michigan 
Ohio University Physics and Astronomy
Columbia University Astronomy and 

MDM Observatory GRB Team

GRB 050502a: Optical follow-up
MDM 1.3m R-band: May 2.163 UT
1.3m First
MDM 1.3m R-band: May 2.431 UT
1.3m Last
(J2000) 13h29m46s.31, +42°40'27".7 (2.2 x 2.2 arcmin)

GCN Circular #3363: GRB 050502a: Optical Observations
N. Mirabal (U. Michigan), M. Boettcher, J. Shields, M. Joshi (Ohio U.),
and J. Halpern (Columbia U.) report on behalf of the MDM GRB follow-up 

"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)."

The data in the following figures are for internal use only.
They should not be reproduced without the permission of the authors.
GRB 050502a Decay Curve
Decay Curve Enlargement

Markus Boettcher
Joe Shields
Nestor Mirabal
Jules Halpern
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Last Modified: May 13, 2005