TITLE: GCN CIRCULAR NUMBER: 11024 SUBJECT: GRB 100728B: Continued KAIT observations DATE: 10/07/29 05:56:35 GMT FROM: Daniel Perley at U.C. Berkeley D. A. Perley, W. Li, and A. V. Filippenko (UC Berkeley) report on behalf of the KAIT GRB follow-up team: The Katzman Automatic Imaging Telescope (KAIT) began observations of GRB 100728B (Morris et al., GCN 11009) at 30 sec after the trigger time (10 sec after the GCN notice), and continued to track the afterglow in a combination of V, I, and unfiltered exposures until shut down by morning twilight. The afterglow remains detected throughout this period. An series of 2-second frames taken between 30-64 sec clearly shows a rapid rise from an initial mag of ~16.5 (calibrated to USNO B1.0) to a peak of 16.1 mag at ~50 seconds. The afterglow decays as an unbroken power-law with decay index alpha=0.97 after that time through the end of our observations at 5700 s. A subset of the unfiltered photometry is presented below: tstart(s) exp(s) mag unc 149 20 17.02 +/- 0.02 249 20 17.61 +/- 0.03 446 20 18.21 +/- 0.05 643 20 18.51 +/- 0.07 846 20 18.90 +/- 0.07 1141 60 19.15 +/- 0.07 1440 60 19.40 +/- 0.07 1668 60 19.76 +/- 0.10 2264 100 19.81 +/- 0.10 3326 100 19.86 +/- 0.08 4186 140 20.33 +/- 0.10 5115 140 20.58 +/- 0.14 5544 200 20.88 +/- 0.19 All times are referenced to the BAT trigger at 10:31:55 UT. Magnitudes are calibrated relative to USNO B1.0 standards in the field. Further analysis is in progress. We note that the I-band magnitude in our previous circular (GCN 11007) was calibrated to USNO R-band standards and should not be relied upon for detailed analysis. In addition, the time from burst specified in that circular is relative to the BAT position notice time, rather than the trigger time as specified. (The UT time given is correct as stated.)