{
  "bibcode": "2014GCN.16338....1M",
  "body": "R. Margutti, E. Berger, R. Chornock, W. Fong, T. Laskar and A. Zauderer\n(Harvard U.) report:\n\n\"We observed the location of GRB 140515A (D'Avanzo et al., GCN 16267)\nat z=6.32 (Chornock et al., GCN 16269)\nwith the Chandra X-ray Observatory (Program 15508477, PI Margutti).\nOur observations started on May 25th, 07:38:38 UT,  858.6 ks after the BAT\ntrigger.\nNo X-ray source is detected at the position of the optical and radio\nafterglow\n(Fong et al., GCN 16274, Laskar et al., GCN 16283),\nwith a 3-sigma count-rate limit of 1.5E-4 c/s (0.3-10 keV energy range,\ntotal exposure time of 19.8 ks).\n\nAdopting the best fitting parameters from the total PC-mode spectrum\n(photon index Gamma=1.8, intrinsic neutral hydrogen column density\nNHint=2.3E+22 cm-2 at z=6.32), we compute an observed flux limit of\n1.5E-15 erg/s/cm2 (0.3-10 keV).  The Galactic hydrogen column density\nin the direction of the burst is NHgal=2.5E+20 cm-2 (Kalberla et al.,\n2005).\nOur observations constrain the late-time (t> 100 ks) X-ray afterglow decay\nto be steeper than t^-2.6.\n\nWe thank Belinda Wilkes and the entire Chandra team for making these\nobservations possible.\"",
  "circularId": 16338,
  "createdOn": 1401303825000,
  "email": "rmargutti@cfa.harvard.edu",
  "subject": "Chandra late-time observations of GRB140515A",
  "submitter": "Raffaella Margutti at Harvard  <rmargutti@cfa.harvard.edu>",
  "eventId": "GRB 140515A"
}