{
  "subject": "GRB 161104A: Chandra X-ray observations",
  "eventId": "GRB 161104A",
  "bibcode": "2016GCN.20166....1M",
  "createdOn": 1478798834000,
  "circularId": 20166,
  "submitter": "Wen-fai Fong at U of Arizona  <wfong@email.arizona.edu>",
  "email": "wfong@email.arizona.edu",
  "body": "R. Margutti (Northwestern U.), E. Berger (Harvard U.), and W. Fong (U.\nArizona) report:\n\n\"We observed the location of the short GRB161104A with the Chandra X-ray\nObservatory (CXO) on 2016 Nov 8th, 14:41:45 UT, 364 ks after trigger (Mingo\net al., GCN 20123) under a pre-approved guest observer program (PI Berger).\nNo X-ray source is detected within the enhanced XRT position (Goad et al.,\nGCN 20124). In particular, we do not find evidence for statistically\nsignificant X-ray emission at the location of the optical source reported\nby Troja  et al., GCN 20137 at RA, Dec = 05:11:34.5, -51:27:33.90.   Using\n19.8 ks of CXO observations we infer a 3 sigma count-rate limit of  3.0E-4\nc/s in the 0.5-8 keV energy range. The neutral hydrogen absorption in the\ndirection of the transient is 1.4E+20 cm-2 (Kalberla et al., 2005).\nAssuming the spectral parameters that best fit the Swift-XRT observations\n(power-law photon index Gamma=1.36  and no evidence for intrinsic neutral\nhydrogen absorption, Burrows et al., GCN 20128) the inferred absorbed\n(unabsorbed) flux limit is Fx< 4.4E-15 erg/s/cm2  (Fx<4.5E-15 erg/s/cm2) in\nthe 0.3-10 keV energy range. Our observations indicate a steepening of the\nX-ray afterglow temporal decay. Starting from 20 ks after trigger, the\nX-ray afterglow decays as t^-alpha with alpha>1.3.\n\nWe thank the CXO team for rapid scheduling of our observations.\""
}