GCN Circular 1757
P. Wozniak, W.T. Vestrand, D. Starr, J. Wren, K. Borozdin, S. Brumby, D. Casperson, M. Galassi, K. McGowan and R. White report: One of our RAPTOR (RAPid Telescopes for Optical Response) telescopes at the Los Alamos National Laboratory responded to HETE trigger 2493 in real-time. Our imaging of the burst location began at 11:19:38.9 UT, 64.9 seconds after the GRB time. The first image, a 60-second exposure, shows an optical transient (OT) at the position identified by Fox and Price (GCN 1731). The OT signal was slightly blended with a nearby star. To correct for the blending we used difference image photometry with reference images obtained after the OT faded below our detection limit. Correlating our unfiltered magnitude with the USNO photometry reported by Henden (GCN 1753) we derive a Rc magnitude of 14.06+/-0.08. Assuming an afterglow flux decay with power-law index alpha=-1.6, the flux-weighted image time is 89.7 seconds after the GRB time. Our measurements are consistent with the suggestion by Chornock et al. (GCN 1754) that the early afterglow was fading more rapidly than the late afterglow. An animation that compares the detection image with an image taken after the object faded below our detection limit will be posted on the RAPTOR website at: www.raptor.lanl.gov This message can be cited.