------------------------------------------------------------------- THE ASTRONOMER Electronic Circular No 2169 2005 Nov 11 19.45UT Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise, Basingstoke, Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074 INTERNET: GUY@TAHQ.DEMON.CO.UK Backup: gmh@wdcc1.bnsc.rl.ac.uk WORLD WIDE WEB http://www.theastronomer.org ------------------------------------------------------------------- GRB051111A (BRIGHT OPTICAL TRANSIENT) Eli Rykoff et. al., University of Michigan, report on GCN 4251 on behalf of the ROTSE collaboration their discovery of a fast fading optical transient inside the error circle for GRB 051111A by the ROTSE-IIIb telescope, located at McDonald Observatory. The initial response was during the BAT emission, when the transient was at 13.0 mag (unfiltered, relative to USNO A2.0). The transient faded as a simple power law with decay index ~ -0.9. At UT 06:41:57 (t+2500s), the transient was at 17.4 mag. On GCN 4252 Grant Williams, Steward Observatory, reported on behalf of the Super-LOTIS collaboration that the 0.6m automated Super-LOTIS telescope responded to Swift trigger 163438, GRB051111A. The first image began at 06:00:17.4 UT, 35.9 s after the burst. They clearly detect the OT identified by W. Rujopakarn et al. and found that it has faded considerably in images taken 15 minutes after the burst. The approximate R band magnitude in the first 10 second exposure was determined using the USNO B1 catalog. UT Start Exp Time R mag delta R 06:00:17.4 10 s 13.2 0.1 A further report from Carole Mundell, JMU, Liverpool, on GCN 4250 indicates that the 2-m Faulkes North Telescope robotically followed up GRB051111A at 06:04:44 UT. The automatic "detection mode" procedure detected a fading candidate at: RA 23:12:33.17 DEC +18:22:28.80 (J2000) - R = 14.86 mag (vs USNOB1) W. Li, University of California, Berkeley, on behalf of the KAIT GRB team relays on GCN 4254: The robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory observed GRB051111A. A series of images was automatically obtained starting at 06:00:25 UT (44s after the burst). The sequence includes a combination of images taken with the V and I filters, as well as some that are unfiltered. The OT identified by W. Rujopakarn et al. (GCN 4247) was detected with the following unfiltered magnitudes (calibrated to USNO B1.0): UT Start EXP time R mag delta R 06:00:25 15 s 13.40 0.05 06:01:46 20 s 14.32 0.05 Jason Prochaska (UCO/Lick) adds on GCN 4255 that the Keck team observed it with HIRESr for 1800s starting UT 07:03. They detected a series of strong MgII, FeII and SiII absorption features at a redshift z=1.55. Because they detected no additional features redward of the MgII doublet, they adopt this as the redshift of GRB 051111. Guy M Hurst