{
  "format": "text/plain",
  "submitter": "Howard E. Bond at Space Telescope Science Institute <bond@stsci.edu>",
  "email": "circulars@gcn.nasa.gov",
  "subject": "GRB 971227: Optical clarifications ",
  "circularId": 22,
  "editedOn": 1720192653691,
  "eventId": "GRB 971227",
  "bibcode": "1997GCN....22....1B",
  "body": "Howard E. Bond (Space Telescope Science Institute)                      #022\nDavid Balam (University of Victoria)\nKailash C. Sahu (Space Telescope Science Institute)\nreport:\n\nThere seems to have been some confusion about possible optical counterparts of \nGRB 971227 in recent GCN e-mails.\n\nWe believe that this is because THREE different optical objects have been\nmentioned in recent communications, as follows: \n\nObject            RA    (J2000)    Dec       Remarks\n\n   1              12h57m10.6s   +59o24'43\"   proposed as GRB counterpart by \n                                             Castro-Tirado et al., IAUC 6800\n\n   2              12h57m08.6s   +59d24'40\"   described as non-variable at \n                                             R=20.4 by Galama et al. (GCN \n                                             notice Dec 31) based on KPNO and \n                                             APO data\n\n   3              12h57m04.8s   +59d24'42\"   reference star with R=19.0 used \n                                             by Galama et al.\n\n\nWe note that objects 1 and 2 ARE NOT IDENTICAL.  Object 2 is in fact faintly\nvisible on direct examination of POSS-II films, in accordance with the above\nreport of non-variability.  Object 1 is NOT visible on POSS-I prints nor the \nPOSS-II films.\n\nA 630-sec CCD R-band exposure on the field was obtained on 1997 Dec 31.44\nby D. Balam under poor observing conditions with the 1.8-m Plaskett reflector\nof the Dominion Astrophysical Observatory; the limiting magnitude (S/N=3) is\nR=20.5 (assuming Object 3 to have R=19.0). Object 2 is faintly visible, in\naccordance with the above. \n\nObject 1, visible at R=19.5 in a Calar Alto image of Dec 27.91 posted on the\nWWW by Castro-Tirado et al. (see IAUC 6800), and reported as NOT seen above\nR=20.5 on Dec 30.16 by Bartolini et al. (GCN notice, Dec 30), is likewise NOT\nvisible above R=20.5 in Balam's image of Dec 31.44. \n\nThis observation would appear to strengthen the reported variability of Object\n1 and its identification with the GRB afterglow. \n\nDeeper images should urgently be obtained and monitoring should continue.",
  "createdOn": 883612800000,
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Tyler Barna at University of Minnesota <tylerpbarna@gmail.com>",
  "version": 2
}