{
  "bibcode": "2015GCN.17516....1S",
  "body": "M. Stamatikos (OSU), S. D. Barthelmy (GSFC),  W. H. Baumgartner (GSFC/UMBC),\nJ. R. Cummings (CPI), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),\nA. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),\nT. Sakamoto (AGU), J. Tueller (GSFC), T. N. Ukwatta (LANL),\nF. Marshall (NASA/GSFC), D. Malesani (DARK/NBI), L. Hagen (PSU),\nM. de Pasquale (INAF-IASFPA), A. Maselli (INAF-IASFPA), D.N. Burrows (PSU),\nK. Page (U. Leicester), N. P. M. Kuin (UCL-MSSL)\n\n  \nUsing the data set from T-60 to T+243 sec from the recent telemetry downlink,\nwe report further analysis of possible GRB 150301C (trigger #633105)\n(Lien, et al., GCN Circ. 17512).  The BAT ground-calculated position is\nRA, Dec = 11.319, 41.861 deg which is\n    RA(J2000)  =  00h 45m 16.6s\n    Dec(J2000) = +41d 51' 40.0\"\nwith an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).\nThe significance in the BAT image was 10.1, so we are sure that this was\na real astrophysical source.  The partial coding was 69%.\n\nThe location is well within the visible light of M31.  A more distant galaxy,\n[JSD2012] 170, which has a size of 0.11 arcmin, is within the BAT error\ncircle.  In 1.9 ks of data, the Swift XRT found only a single very weak source\n(2.8 sigma), consistent with the position of a known source within the BAT\nerror circle, [PFH2005] 622, with a count rate of (5.3+/-1.9) x 10^-03 c/s.  We\ncannot state whether there is any variability of this source at this time.  The\nXRT position of this source is:\n\nRA (J2000)  00h 45m 14.4s\nDec (J2000) +41d 50' 37.7\"\n\nThe BAT mask-weighted light curve shows a single weak FRED peak.  T90 (15-350 keV)\nis 14 +- 3 sec (estimated error including systematics).\n  \nThe time-averaged BAT spectrum from T-0.6 to T+15.0 sec is best fit by a power-\nlaw model with an exponential cutoff.  The power law index of the time-averaged\nspectrum is poorly defined but is nominally -0.8 +- 2.  The peak energy is\n38 +- 7 keV.  The fluence in the 15-150 keV band is 2.1 +- 0.4 x 10^-07 erg/cm2.\nThe 1-sec peak photon flux measured from T+1.32 sec in the 15-150 keV band is\n0.6 +- 0.2 ph/cm2/sec.  A simple power-law fit has a photon index of 1.96 +- 0.25.\nAll the quoted errors are at the 90% confidence level.\n\nIf this source was in M31, its isotropic energy output was 1.5 x 10^43 ergs\nin 15.6 seconds in the range 15-150 keV.\n\nIt is very possible, given the softness of the source, that this is a non-GRB\nin M31.  The color:duration is within the distribution of long GRBs.  No XRT\nsource was seen in the initial observations, whereas we might expect most\nsources in M31 bright enough to be seen in BAT would be very bright in XRT.\nTherefore the source is likely to be highly absorbed.  The results of the\nbatgrbproduct analysis are available at\nhttp://gcn.gsfc.nasa.gov/notices_s/633105/BA/\n\nThe Swift/UVOT began settled observations of the field 102 s after\nthe BAT trigger (Lien et al., GCN Circ. 17512). No new source within\nthe BAT error circle is detected in the initial UVOT exposures.\nPreliminary 3-sigma upper limits using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first\nexposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nwhite              102         4151          369        >20.39\nv                  592         4562          216        >18.55\nb                  518         5241           96        >19.08\nu                  261         5177          461        >19.69\nuvw1               641         4973          216        >19.27\nuvm2               617         4768          216        >19.20\nuvw2               568         4357          216        >19.41\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.06 in the direction of the burst\n(Schlegel et al. 1998).\n\nFurther Swift observations are planned.\n\n[GCN OPS NOTE(01mar15): Per author's request, the affiliation was corrected for KP.]",
  "circularId": 17516,
  "createdOn": 1425241862000,
  "email": "james.r.cummings@nasa.gov",
  "subject": "GRB 150301C : (Swift trigger 633105) Swift observations",
  "submitter": "Jay R. Cummings at NASA/GSFC/Swift  <james.r.cummings@nasa.gov>",
  "eventId": "GRB 150301C"
}