//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19731 SUBJECT: GRB 160726A: Swift detection of a short burst DATE: 16/07/26 01:50:31 GMT FROM: Kim Page at U.of Leicester R. L. C. Starling (U Leicester), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and T. Sakamoto (AGU) report on behalf of the Swift Team: At 01:34:07 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160726A (trigger=706052). Swift did not slew immediately due to an observational constraint. The BAT on-board calculated location is RA, Dec 98.821, -6.644 which is RA(J2000) = 06h 35m 17s Dec(J2000) = -06d 38' 39" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 1 sec. The peak count rate was ~14000 counts/sec (15-350 keV), at ~0.7 sec after the trigger. Due to a Sun observing constraint, Swift cannot slew to the BAT position until 12:53 UT on 2016 August 10. There will thus be no XRT or UVOT data for this trigger before this time. Burst Advocate for this burst is R. L. C. Starling (rlcs1 AT star.le.ac.uk). 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: 19732 SUBJECT: GRB 160726A: Fermi GBM observation DATE: 16/07/26 08:28:00 GMT FROM: Elisabetta Bissaldi at U.Innsbruk/IAPP R. Hamburg (UAH), E. Burns (UAH), and E. Bissaldi (Politecnico & INFN Bari) report on behalf of the Fermi GBM Team: "At 01:34:07.72 UT on 26 July 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160726A (trigger 491189651 / 160726065), which was also detected by the Swift/BAT (Starling et al. 2016, GCN 19731). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi-LAT boresight at the GBM trigger time is 50 degrees. The GBM light curve consists of two short peaks with a duration (T90) of about 0.7 s (50-300 keV). The time-averaged spectrum from T0-0.06 s to T0+0.77 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.0 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 540 +/- 100 keV. The event fluence (10-1000 keV) in this time interval is (1.01 +/- 0.05)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.06 s in the 10-1000 keV band is 5.5 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19733 SUBJECT: Konus-Wind observation of short GRB 160726A DATE: 16/07/26 14:14:21 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report: The short GRB 160726A (Swift/BAT detection: Starling et al., GCN 19731; Fermi GBM observation: Hamburg et al., GCN 19732) triggered Konus-Wind at T0=5645.315 s UT (01:34:05.315). The light curve shows a short pulse with a total duration is ~0.2 s. The emission is seen up to ~2 MeV. As observed by Konus-Wind, the burst had a fluence of (1.5 ± 0.5)x10^-6 erg/cm2 and a 16-ms peak energy flux, measured from T0+0.016, of (1.1 ± 0.3)x10^-5 erg/cm2 (both in the 20 keV - 10 MeV energy range). The spectrum of the burst (measured from T0 to T0+0.128 s) is best fit in the 20 keV - 2 MeV range by a cutoff power-law (CPL) function with the following model parameters: the photon index alpha = -0.65(-0.47,+0.71), and the peak energy Ep = 424(-163,+389) keV, chi2 = 19.5/20 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep with only an upper limit on beta of -1.8, chi2 = 19.5/19 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB160726_T05645/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19734 SUBJECT: GRB 160726A, Swift-BAT refined analysis DATE: 16/07/27 01:18:02 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), J. P. Norris (BSU), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), R. L. C. Starling (U Leicester), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160726A (trigger #706052) (Starling et al., GCN Circ. 19731). The BAT ground-calculated position is RA, Dec = 98.809, -6.617 deg which is RA(J2000) = 06h 35m 14.2s Dec(J2000) = -06d 37' 03.0" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 58%. The mask-weighted light curve shows a double-peaked structure that starts at ~T0 and ends at ~T+0.8 s, with the two peaks at ~ T0 and ~T+0.6 s, respectively. T90 (15-350 keV) is 0.7 +- 0.04 sec (estimated error including systematics). The time-averaged spectrum from T+0.0 to T+0.8 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.26 +- 0.13. The fluence in the 15-150 keV band is 2.6 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.11 sec in the 15-150 keV band is 3.2 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. Using a 4-ms binned light curve, the lag analysis finds a lag of is -3.5 +/- 3 ms for the 100-350 keV to 25-50 keV, and -5 +/- 6 ms for the 50-100 keV to 15-25 keV band. These numbers are consistent with those of a short GRB. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/706052/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19751 SUBJECT: GRB 160726A: CALET Gamma-Ray Burst Monitor detection DATE: 16/08/01 21:03:22 GMT FROM: Takanori Sakamoto at AGU Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) and the CALET collaboration: The short-duration GRB 160726A (Starling, et al., GCN circ. 19731; Hamburg, et al., GCN circ. 19732; Frederiks, et al. GCN circ. 19733) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 01:34:08.25 on 26 July 2016. The burst signal was seen by all CGBM instruments. The light curve of the SGM shows two peaks. The first weak episode peaks at T-0.55 s. The second peak starts at T-0.1 s, peaks at T+0.1 s and ends at T+0.3 s. The T90 duration measured by the SGM data is 0.83 +- 0.09 sec (40-1000 keV). The light curve is available at http://cgbm.calet.jp/cgbm_trigger/flight/1153531947/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.