TITLE: GCN CIRCULAR NUMBER: 23 SUBJECT: Untitled DATE: 70/01/01 00:00:00 GMT FROM: circulars@gcn.nasa.gov Dave Balam additionally reports: A precise optical position of Object 3 in our previous report has been determined as follows: 12h 57m 04s.93 +59o 24' 39".1 (J2000) The astrometric solution was obtained using 17 USNO catalog stars, m.e. 0".41 (RA) and 0".32 (Dec) [The "previous report" referred to above is attached below for reference. SDB] -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Howard E. Bond (Space Telescope Science Institute) David Balam (University of Victoria) Kailash C. Sahu (Space Telescope Science Institute) report: There seems to have been some confusion about possible optical counterparts of GRB 971227 in recent GCN e-mails. We believe that this is because THREE different optical objects have been mentioned in recent communications, as follows: Object RA (J2000) Dec Remarks 1 12h57m10.6s +59o24'43" proposed as GRB counterpart by Castro-Tirado et al., IAUC 6800 2 12h57m08.6s +59d24'40" described as non-variable at R=20.4 by Galama et al. (GCN notice Dec 31) based on KPNO and APO data 3 12h57m04.8s +59d24'42" reference star with R=19.0 used by Galama et al. We note that objects 1 and 2 ARE NOT IDENTICAL. Object 2 is in fact faintly visible on direct examination of POSS-II films, in accordance with the above report of non-variability. Object 1 is NOT visible on POSS-I prints nor the POSS-II films. A 630-sec CCD R-band exposure on the field was obtained on 1997 Dec 31.44 by D. Balam under poor observing conditions with the 1.8-m Plaskett reflector of the Dominion Astrophysical Observatory; the limiting magnitude (S/N=3) is R=20.5 (assuming Object 3 to have R=19.0). Object 2 is faintly visible, in accordance with the above. Object 1, visible at R=19.5 in a Calar Alto image of Dec 27.91 posted on the WWW by Castro-Tirado et al. (see IAUC 6800), and reported as NOT seen above R=20.5 on Dec 30.16 by Bartolini et al. (GCN notice, Dec 30), is likewise NOT visible above R=20.5 in Balam's image of Dec 31.44. This observation would appear to strengthen the reported variability of Object 1 and its identification with the GRB afterglow. Deeper images should urgently be obtained and monitoring should continue.