TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5176 SUBJECT: GRB 060526: Optical Flare DATE: 06/05/27 23:08:55 GMT FROM: Jules Halpern at Columbia U. J. P. Halpern (Columbia U.), E. Armstrong (UCSD), & N. Mirabal (U. Michigan) report on behalf of the MDM Observatory GRB follow-up team: "Using the MDM 1.3m telescope on Kitt Peak, we obtained a continuous R-band time series of the afterglow of Swift GRB 060526 (Campana et al. GCN 5162), consisting of 40 10-minute exposures, from 11.0 to 18.2 hours after the burst. Preliminary photometry was performed using comparison stars in r' from the SDSS calibration (Cool et al. GCN 5164). In addition, wherever possible, we placed other GCN reported R-band photometry (Covino et al. GCN 5167; Khamitov et al. GCN 5173; Morgan & Dai GCN 5175) on a common scale using the SDSS r' magnitudes of their indicated comparison stars. As a result, we find that a power-law decay index of -1.18 +/- 0.05 fitted to the Khamitov et al. data alone from 5.6 to 8.9 hours also fits the MDM light curve very well, until about 16 hours after the burst. At that time, a flare began that had a rise time of about 40 minutes, followed by a slower decay, and had not yet returned to the extrapolated power law when the observations were terminated at twilight. The peak of the flare occurred around May 27 09:06 UT, and reached about 0.3 magnitudes above the extrapolation. In combination with the multiple episodes of gamma-ray and X-ray emission (Campana et al. GCNs 5163, 5168; Markwardt et al. GCN 5174) and the long plateau in the early optical light curve (Rykoff et al. GCN 5166), these results indicate the possibility of extended and complex activity from GRB 060526 that warrants intensive monitoring. A preliminary version of the MDM optical light curve and incorporated GCN data is available at http://www.astro.columbia.edu/~jules/grb/060526/ The data contained in the figure are not yet suitable for publication."