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TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2338 SUBJECT: XRF030723: Re-analysis of ROTSE-III early images DATE: 03/07/30 17:33:21 GMT FROM: Don Smith at U michigan <dasmith@rotse2.physics.lsa.umich.edu> D. A. Smith, C. W. Akerlof (U. of Michigan) and R. Quimby (U of Texas Austin) report on behalf of the ROTSE collaboration: We have re-analyzed the ROTSE-III early observations of event 030723 (See Smith & Quimby, GCN Circ. #2318 for details on the ROTSE observations) after the report of the counterpart candidate discovered by Fox et al. (GCN Circ. #2323). We performed a fit to a template PSF placed at a list of targets selected from Henden's photometry report (GCN Circ. #2317). We find no convincing evidence for a detection of the OT in the first four of our images, but the last two images do yield marginal possible detections. We derive 19.5+-0.4 for the fifth image (S/N=2.7) and 19.3+-0.4 for the sixth (S/N=3.1). We derive the following 2-sigma upper limits on the OT magnitude for each image, as calibrated to the R band values given by Henden: Time from burst (min): 0.79 3.2 8.1 19.7 31.3 42.9 R band magnitude : >19.0 >19.7 >19.1 >19.5 >18.9 >18.8 Note that these numbers are not limiting magnitudes for each image but upper limits to the brightness of an object at the OT location. Also, the ROTSE images are unfiltered, and since no color information is available for the early afterglow, we have not applied any color correction to this calibration.
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