{
  "bibcode": "2007GCN..6769....1K",
  "body": "Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:\n\nDuring the night 30-31 August 2007,\nwe imaged six times a 2x2 degrees field\ncentered on RA=18h47.3min DEC=-63d20m (J2000,0)\nto search supernovae.\n\nDates of beginning of exposures are following:\n\n#1 2007-08-31T00:20:38.69 exposure=120s, filter=R\n#2 2007-08-31T00:22:44.56 exposure=120s, filter=R\n#3 2007-08-31T01:16:47.89 exposure=120s, filter=R\n#4 2007-08-31T01:18:53.76 exposure=120s, filter=R\n#5 2007-08-31T02:22:15.39 exposure=120s, filter=R\n#6 2007-08-31T02:24:21.26 exposure=120s, filter=R\n\nWe detect a bright like-star object R=11.7\nonly in the #5 image, at coordinates:\n\nRA=18h50m32s0 DEC=-63d01m00s3 (J2000,0)\n\nThis object is at 18 arcsec S-E of the IC 4779 nucleus\n(redshift z=0.016752 from NED).\n\nNone is seen at this place in other images,\nimplying R>18.5.\n\nScreen copies of images are available at:\n\nhttp://www.cesr.fr/~klotz/ic4779/\n\nAll the evidence available at that time is in favor\nof a real astronomical optical transient (hereafter OT).\nThe 2D profile of the OT is very close to that of\nthe PSF derived from nearby stars of same magnitude\n(OT spreads on about 25 pixels). An artificial satellite\nor a plane flashlight are rejected because none is\nseen in the #6 image.\n\nWe suggest that if this OT is an astronomical\ntransient, one hypothesis is an optical flash\noccurring when a short burst (SHGRB) is active in\ngamma wavelengths. This idea is supported\nby the fact the #6 image taken just after the #5 one\ndoes not show the OT. Moreover, the low distance\nof IC 4779 is compatible with a host galaxy\nof SHGRB.\n\nWe remind that, due to their very short durations (<0.2s)\nno optical telescope had ever observed a SHGRB\nduring its gamma emission phase.\n\nWe are currently regarding other possibilities than\na GRB (a cosmic trace is almost excluded at\nthe current step of analysis).\n\nComplementary observations are strongly encouraged.\nSome suggestions to do to confirm a SHGRB are:\n\n- Searching in large field surveys archives\n   at the #5 image date. Following table indicates\n   the expected magnitudes reached for various duration\n   of the optical transient during the exposure:\n   R=11.7 if duration=120 sec.\n   R=9.0 if duration=10 sec.\n   R=6.5 if duration=1 sec.\n\n- Deep image at OT position (mag lim > 23)\n   as soon as possible with a very large telescope.\n\n- Searching in the high-energy satellites\n   archive to find a SHGRB signal\n   at the #5 image date.\n\nFITS files are available asking to alain.klotz@free.fr\n\nThis message may be cited.",
  "circularId": 6769,
  "createdOn": 1188594218000,
  "email": "Alain.Klotz@free.fr",
  "subject": "Orphan GRB candidate in IC 4779 at TAROT La Silla observatory",
  "submitter": "Alain Klotz at CESR-CNRS  <Alain.Klotz@free.fr>"
}