GCN Circular 915
Optical observations of GRB 001018 with JCAM J. S. Bloom, A. Diercks, S. R. Kulkarni, F. A. Harrison, (Caltech), B. B. Behr (U. Texas), J. C. Clemens (UNC) report on behalf of the larger GRB-NRAO-CARA GRB collaboration: "On 18 December 2000 UT, J. Bloom and D. Reichart observed the field of GRB 001018 (Hurley et al., GCN #853) near the transient radio position reported by Taylor et al. (GCN #857) on the Palomar 200-inch telescope during a commissioning run of the Jacobs Camera (JCAM), a dual-CCD imager designed primarily for rapid follow-up of GRB afterglow. The plate scale of JCAM is 0.38 arcsec/pixel and the field-of-view is 3.2 x 3.2 arcmin^2. We observed the GRB field simultaneously in R- and B-band for a total of 2700s. An astrometric plate solution was obtained using 10 (11) ties stars common to both the USNO-A2.0 catalogue and the R- (B-) band summed image. The total absolute astrometric uncertainty in the R-band plate solution was 0.32", 0.27" in RA and Dec. Unfortunately, the seeing (2.8 arcsec FWHM in R-band) was very poor at Palomar on 18 December and there was significant extinction due to cirrus. At the position of Taylor's radio transient there were no detected objects to R~22.7 mag (5-sigma); the photometric zeropoint was estimated using the USNO stars in the field." The R and B finding chart images of the may be obtained at: http://www.astro.caltech.edu/~jsb/GRB/grb001018/ For further information on JCAM, please see: http://www.astro.caltech.edu/~jsb/Jcam This message may be cited.