TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2066 SUBJECT: GRB030329: further optical photometry and evidence for a light curve discontinuity DATE: 03/04/02 01:00:07 GMT FROM: Karl Glazebrook at Johns Hopkins J. Tober, E. Hoverstein, K. Chiu, K. Glazebrook We have observed the optical afterglow of GRB 030329 with the 20in Morris W. Offit telescope of the Maryland Space Grant Consortium Observatory. The telescope is located in downtown Baltimore, Maryland and the observations were made with a student built CCD camera on the night of March 31st / morning of April 1st with an R-band filter. Aperture photometry was made with APPHOT in a 20 arcsec diameter aperture with errors empirically estimated from the background noise. The photometry is computed by assuming the USNO reference star at RA 10 44 42.01 DEC +21 32 31.8 has constant magnitude R=16.2 but counts were consistent from run to run indicating near-photometric conditions. The GRB appeared to brighten suddenly between ~02:30 and ~03:30 by 0.5 mags and then fade slowly for the next few hours. Table 1. R-band Observations. Magnitudes and errors. Times (t) are in minutes from 02:33 UT on April 01, 2003 and refer to the middle of stacked sequences of ~25 minute exposures. t Star1 Star3 Star5 GRB 0 13.749 0.007 16.257 0.069 16.904 0.126 17.457 0.207 52 13.696 0.007 16.104 0.064 16.617 0.108 16.844 0.130 *** Jump ? 117 13.778 0.007 16.275 0.069 16.931 0.128 17.056 0.141 165 13.826 0.007 16.198 0.062 16.884 0.108 17.169 0.154 209 13.637 0.008 16.076 0.070 16.538 0.104 16.940 0.153 The error on the reference star was +/- 0.07 which should be added in quadrature to the above table. (Note star 1 is off the nominal R=14.00 value which we attribute to non-linearity in the CCD) This photometry is preliminary, further analysis is proceeding. The reference stars are indicated at: http://mrhanky.pha.jhu.edu/~kgb/GRB030329/grb-circ-finder.jpg A plot of the light curve is available from: http://mrhanky.pha.jhu.edu/~kgb/GRB030329/grbplot2.ps The Maryland Space Grant Consortium Observatory is supported by NASA's National Space Grant College and Fellowship Program. Further information is available at: http://henry.pha.jhu.edu/msgc/observatory.html