{
  "bibcode": "2010GCN.10524....1S",
  "body": "T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),\nJ. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), C. B. Markwardt (GSFC/UMD), \nD. M. Palmer (LANL), M. Stamatikos (GSFC/OSU) \n(i.e. the Swift-BAT team):\n\nUsing the BAT hard X-ray survey data (Detector Plane Histogram data), we have \nprocessed the BAT survey data for pre- and post-trigger periods using the batsurvey \nscript and have extracted the flux at the location of the GRB.  While Swift was pointing at \nGRB 100316C from T-2650 s to T-80 s, the GRB 100316D location was in the FOV of BAT.  \nAt 12:43, Swift slewed to a pre-planned target (1E 1048.1-5937), and triggered on GRB 100316D.  \nAfter re-pointing to the location of GRB 100316D, Swift slewed away from GRB 100316D \nat T+750 s due to an observational constraint.  GRB 100316D came back into the FOV of BAT \nat T+5050 s (a pre-planned observation of 1E 1048.1-5937).  \n\nThe BAT light curve in the 14-195 keV band around the trigger time is available at:\n\n-Light curve from T-6000 sec to T+6000 sec:\nhttp://gcn.gsfc.nasa.gov/other/GRB100316D_bat_lc.gif\n\n-Zoom-in light curve from T-2000 sec to T+1000 sec:\nhttp://gcn.gsfc.nasa.gov/other/GRB100316D_bat_lc_zoomin.gif\n\nThe light curve produced by the BAT event-by-event data is overlaid with the survey light \ncurve in the figure. There is a probable early low-level emission starting from T-1500 s. \nThe emission then rises at T-500 s, peaks at T-100 s, and decays with an exponential \ndecay constant of ~750 s.  The emission continues through the slew at T+750 s.  \nThe emission is no longer detected by BAT after T+5050 s.\n\nAs pointed out in Sakamoto et al. (GCN Circ. 10511), the BAT light curve profile of \nGRB 100316D is very similar to the GRB 060218-SN2006aj burst \n(Camapana, et al.; Nature, v224, p1008).  The BAT light curve of GRB 060218 shows \na rise at T-300 s, a peak at T+450 s, and an exponential decay constant of ~500 s, \nwith a duration of ~2000 sec.  GRB 100316D was detected in Swift-BAT from ~T-500 sec \nto at least ~T+800 sec, hence the lower limit on the duration of GRB 100316D is ~1300 sec.  \nThe fluence in the 15-150 keV band measured with the available 955 seconds of event data \nis 3.4 x 10^-6 erg/cm2.  This corresponds to an isotropic equivalent \nenergy (Eiso) of 3.1x10^49 ergs in the 15.88 keV - 158.85 keV band at the GRB rest frame \nassuming a redshift z=0.059 of a potential source and a galaxy inside the XRT error \ncircle (Vergani et al. GCN Circ. 10512, 10513).  This unusually long duration in \nconcert with a soft spectrum and a low Eiso (Eiso of GRB 060218 was  \n6.2x10^49 ergs) strengthens the similarity between GRBs 100316D and 060218.  Although \nthe lack of a clear optical counterpart to GRB 100316D at this stage is distinctly \ndifferent than GRB 060218, the prompt emission characteristics are very much like \nsupernova-associated GRB 060218.  Hence, we suggest additional follow-up observations \nespecially in the IR that may confirm the presence of a host supernova.",
  "circularId": 10524,
  "createdOn": 1268946839000,
  "email": "takanori@milkyway.gsfc.nasa.gov",
  "subject": "GRB 100316D: Pre-burst emission measured by BAT",
  "submitter": "Takanori Sakamoto at NASA/GSFC  <takanori@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 100316D"
}