{
  "bibcode": "2016GCN.20053....1B",
  "body": "S. D. Barthelmy (GSFC), P.A. Evans (U Leicester), N. Gehrels (GSFC),\nA. Y. Lien (GSFC/UMBC), J. P. Norris (BSU), P. O'Brien (U Leicester),\nK. L. Page (U Leicester), J. L. Racusin (NASA/GSFC),\nand H. Ziaeepour report on behalf of the Swift Team:\n\nWe performed further analysis of GRB161004A (trigger #715084;\nEvans et al., GCN Circ. 19979), to explore the possibility to\nclarify its short/long nature.\n\nUsing the full BAT event data set from T-240 to T+962 sec,\nthe updated T90 is 3 +/- 1.4 s (using the 1-s binned light curve).\nThis T90 is longer than the 1.08 +- 0.21 s originally reported\n(Palmer et al, GCN Circ. 20001). However, we note that due to\nthe weakness of the burst, the standard pipeline finds a T90 that\nvaries from ~ 1.3 s to ~ 3 s when using light curves with different\nbin sizes.\n\nThe image analysis with the BAT data in 15-150 keV finds no significant\ndetections for extended emission within several hundred seconds\nafter the trigger. However, the BAT image from T+250 s to T+350 s,\nwhich is the time period around the peak of the XRT flare,\ndoes show a slight increase of significance of 3.8 sigma (comparing\nto ~ 1 to 2 sigma detections for other periods). Therefore, it is possible\nthat the XRT flare might be the second peak of the prompt emission, but\nwas close to the detection limit of the BAT.\n\nThe time averaged spectrum is best fit by a simple power-law model,\nwith an index of 1.3 +/- 0.33. This value is consistent with the average\nvalue of the short GRB distribution, and slightly on the harder side of the\nlong burst distribution, but still within the majority (Lien & Sakamoto et al.\n2016).\n\nThe lag analysis is still unavailable due to the weakness of the burst\n(Palmer et al, GCN Circ. 20001).\n\nThe bright flare in the XRT light curve around T+300 s is unusual\nfor short GRBs. However, Swift have detected short GRBs with\nflares before (e.g., GRB 070724A, GRB 100816A; Margutti et al., 2011,\nMNRAS, 417, 2144), and thus we cannot rule out the short-burst\npossibility base on this.\n\nTherefore, we conclude that the burst nature remains ambiguous\nwith current information.",
  "circularId": 20053,
  "createdOn": 1476576411000,
  "email": "amy.y.lien@nasa.gov",
  "subject": "GRB161004A: Further analysis of the burst nature",
  "submitter": "Amy Lien at GSFC  <amy.y.lien@nasa.gov>",
  "eventId": "GRB 161004A"
}