//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13779 SUBJECT: GRB 120918A: Swift detection of a burst DATE: 12/09/18 11:26:07 GMT FROM: David Palmer at LANL B. N. Barlow (PSU), W. H. Baumgartner (GSFC/UMBC), C. Gronwall (PSU), D. M. Palmer (LANL), M. Stamatikos (OSU/NASA/GSFC) and B.-B. Zhang (PSU) report on behalf of the Swift Team: At 11:16:10 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 120918A (trigger=534015). Swift could not slew to the burst because of the Sun constraint. The BAT on-board calculated location is RA, Dec 181.054, -32.758 which is RA(J2000) = 12h 04m 13s Dec(J2000) = -32d 45' 26" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 50 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 17:37 UT on 2012 November 15. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is B. N. Barlow (bnb2 AT psu.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 13784 SUBJECT: GRB 120918A: Swift-BAT refined analysis DATE: 12/09/19 21:43:17 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), B. N. Barlow (PSU), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from recent telemetry downlinks, we report further analysis of BAT GRB 120918A (trigger #534015) (Barlow, et al., GCN Circ. 13799). The BAT ground-calculated position is RA, Dec = 181.042, -32.762 deg, which is RA(J2000) = 12h 04m 10.1s Dec(J2000) = -32d 45' 43.5" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 15%. The mask-weighted light curve shows several overlapping peaks starting at ~T-5 sec, the main peak at ~T+1 sec, and ending at ~T+40 sec. T90 (15-350 keV) is 25.1 +- 2.5 sec (estimated error including systematics). The time-averaged spectrum from T-2.86 to T+23.90 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.00 +- 0.39, and Epeak of 85.5 +- 36.3 keV (chi squared 55.6 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.7 +- 0.6 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T-0.28 sec in the 15-150 keV band is 4.5 +- 0.5 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.60 +- 0.09 (chi squared 63.5 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/534015/BA/