GCN Circular 1334
D.W. Fox, P.A. Price, and S.A. Yost (Caltech), with R. Burruss (Palomar Observatory), C.G. Tinney (AAO), and M. Begam and B.P. Schmidt (RSAA, ANU) report: "We have observed the error box of GRB 020331 (GCN #1315) with the Palomar Hale 200-inch telescope + LFC at 2002 Apr 1.40 and 2.38 UT in Sloan i'. Our observations cover the full burst localization to a limiting equivalent R-band magnitude (derived by reference to a single USNO star) of R ~ 23 mag. Visual inspection of the difference image reveals one afterglow candidate at coordinates RA: 13:16:09.54 Dec: -17:55:15.9 J2000 with an estimated uncertainty of 0.5 arcsec in each coordinate. The candidate faded by 0.6 mag between the two observations, implying a power-law decay index of alpha ~ 0.6, which would be unusual for a normal afterglow. The candidate was R ~ 21 mag at the epoch of our first observation, 17 hours after the burst trigger time of Mar 31.689 UT (GCN #1315). The candidate is weakly detected on earlier images from the SSO 40-inch telescope, obtained Mar 31.78, which have a limiting magnitude of R ~ 19.5 mag. The source is also detected on Mar 31.79 Ks-band images from the AAT (c.f. GCN #1322). The candidate is not visible on the second Digitized Sky Survey. A finding chart for the candidate may be found at: http://darkalf.caltech.edu/~pap/grb020331finder.ps This message may be cited."