{
  "bibcode": "2012GCN.13400....1C",
  "body": "S. Campana (INAF-OAB), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI),\nA. J. Levan (U. Warwick) on behalf of a larger collaboration report:\n\nwe imaged for 10 ks the field of GRB 120624B (Gruber et al. 2012, GCN\n13377) with the Chandra ACIS-S starting on June 30, 2012 8:56:22 UT.\nWithin the Swift/BAT 1 arcmin error circle (Barthelmy et al. 2012, GCN 13381)\nwe detect two sources, already reported by Swift/XRT (Littlejohns et al.  2012,\nGCN 13394).\n\nS1 source is detected with wavdetect at a (preliminary) position:\nRA(J2000):  11 23 32.31\nDec(J2000):+08 55 42.8\nThe nominal positional error (90% c.l.) is 0.3 arcsec\n(not including any statistical error).\nThe source is detected with 25 counts.\n\nS2 source is detected with wavdetect at a (preliminary) position:\nRA(J2000):  11 23 28.09\nDec(J2000):+08 55 57.0\nThe nominal positional error (90% c.l.) is 0.2 arcsec\n(not including any statistical error).\nThe source is detected with 49 counts.\n\nWe do not detect any X-ray source at the position of\nthe NIR afterglow candidate (D'Avanzo et al. 2012, GCN13391).\n\nWe note that S1 is brighter than S2 in Swift/XRT observations.\nThe contrary occurs in the Chandra observation.\n\nWe extrapolate the Swift XRT rates based on the Swift/XRT spectrum\n(Galactic column density of 3.6e20 cm-2, intrinsic column density of\n2.4e21 cm-2 at redshift zero and a power law photon index of 2.52).\nAssuming this spectrum for both sources, we predict\n78 counts for S1 and 59 counts for S2, with large uncertainties due to\nspectral modeling and statistics.\n\nDespite this, the disagreement between Swift/XRT predictions (78 counts)\nand Chandra observation (25 counts), likely indicate that S1 is the \nafterglow of GRB120624B.\n\nWe thank Chandra director (H. Tananbaum) for granting this observation\nunder the DDT program.",
  "circularId": 13400,
  "createdOn": 1341169464000,
  "email": "sergio.campana@brera.inaf.it",
  "subject": "GRB120624B: Chandra observations and afterglow detection",
  "submitter": "Sergio Campana at INAF-OAB  <sergio.campana@brera.inaf.it>",
  "eventId": "GRB 120624B"
}