Gamma-ray Burst 131001A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

• none

• GCN Circular #15281
  J. R. Cummings (UMBC/GSFC) reports on behalf of the Swift-BAT team:
  At 2013-10-01T05:37:24, while Swift was slewing, GRB 131001A occurred. The BAT lightcurve shows a single 5-second long FRED peak. In a mosaic of images created from BAT slew data, a significant source was found at RA, Dec 8.302, +25.557, which is

  RA  (J2000)   00h 33m 12.4s
  Dec (J2000)   25d 33' 27"
  

  with an estimated 90% uncertainty radius of 1.8 arcmin.
  A Swift TOO has been requested to locate the X-ray afterglow, and approved with the source ID number20297. Observations are in progress.
• GCN Circular #15288
  A. A. Breeveld (UCL-MSSL), D. Grupe (PSU) and J. R. Cummings (UMBC/GSFC) report on behalf of the Swift team:
  The Swift/UVOT began settled observations of the field of GRB 131001A 79990 s after the BAT trigger (Cummings et al., GCN Circ. 15281). No optical afterglow consistent with the BAT position (Cummings et al., GCN Circ. 15281) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposures are:

  Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
  
  u                79990        86246          972         >20.94
  

  The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).
  The Swift XRT observed the field of GRB 131001A for a total of 972s. No source was found in the BAT error circle. The 3 sigma upper limit at the position of GRB 131001A applying the method described in Kraft et al. (1991, ApJ, 374, 344) is 0.01 counts/s.
  This circular is an official product of the Swift team.
• GCN Circular #15293
  J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
  We report further analysis of BAT GRB 131001A (Cummings, GCN Circ. 15281). The BAT ground-calculated position is RA, Dec = 8.304, 25.557 deg which is

      RA(J2000)  =  00h 33m 13.0s
      Dec(J2000) = +25d 33' 26"
  

  with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 50%.
  The mask-weighted light curve shows a single FRED peak. T90 (15-350 keV) is 4.9 +- 0.3 sec (estimated error including systematics).
  The time-averaged spectrum from T0 to T+5 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.8 +- 0.6, and Epeak of 55 +- 14 keV (chi squared 55.6 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 4.9 +- 0.6 x 10^-7 erg/cm2 and the 1-sec peak flux measured from T+5.49 sec in the 15-150 keV band is 2.57 +- 0.25 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.81 +- 0.12 (chi squared 66.2 for 57 d.o.f.). All the quoted errors are at the 90% confidence level.
  Since this burst was ground-detected the usual automated results of the batgrbproduct analysis are not available.