//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19794 SUBJECT: GRB 160815A: Swift detection of a burst DATE: 16/08/15 12:16:28 GMT FROM: David Palmer at LANL C. B. Markwardt (NASA/GSFC), P.A. Evans (U Leicester), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), B. Mingo (U Leicester), K. L. Page (U Leicester), T. Sakamoto (AGU) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 11:45:11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160815A (trigger=708598). Swift slewed immediately to the burst. The BAT location calculated from the downlinked detector histogram is RA, Dec 288.733, 84.282 which is RA(J2000) = 19h 14m 56s Dec(J2000) = +84d 16m 55.2s with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). No BAT lightcurve is immediately available due to a gap in TDRSS coverage. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 288.5364, 84.3138 which is equivalent to: RA(J2000) = 19h 14m 08.73s Dec(J2000) = +84d 18' 49.8" with an uncertainty of 2.0 arcseconds (radius, 90% containment). This location is 134 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (7.52 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.6 (+1.72/-1.57) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 309 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Data from the 2.7'x2.7' sub-image are not available at this time. The 8'x8' region for the list of sources generated on-board covers none of the BAT error circle. No correction has been made for extinction. Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt AT nasa.gov). 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: 19795 SUBJECT: GRB 160815A: Swift/UVOT Afterglow Detection DATE: 16/08/15 13:03:44 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and C. B. Markwardt (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT has discovered an optical afterglow for GRB 160815A (Markwardt et al., GCN Circ. 19794) in an exposure with the white filter. The preliminary UVOT position is: RA (J2000) = 19:14:09.63 = 288.5401 (deg.) Dec (J2000) = +84:18:50.4 = 84.3140 (deg.) with an estimated uncertainty of 1.0 arcsec. (radius, 90% confidence). The preliminary magnitude using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) is: Filter T_start(s) T_stop(s) Exp(s) Mag white 863 1013 150 19.1 The magnitude is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.12 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19796 SUBJECT: GRB 160815A: Enhanced Swift-XRT position DATE: 16/08/15 16:24:47 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1093 s of XRT Photon Counting mode data and 2 UVOT images for GRB 160815A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 288.54101, +84.31383 which is equivalent to: RA (J2000): 19h 14m 9.84s Dec (J2000): +84d 18' 49.8" with an uncertainty of 1.7 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19797 SUBJECT: GRB 160815A: Fermi GBM detection/observation DATE: 16/08/16 03:00:47 GMT FROM: Rachel Hamburg at UAH R. Hamburg (UAH) reports on behalf of the Fermi GBM Team: "At 11:45:11.64 UT on 15 August 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160815A (trigger 492954315 / 160815490) which was also detected by the Swift/BAT (Markwardt et al., GCN Circ. 19794) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 37 degrees. The GBM light curve consists of two peaks with a duration (T90) of about 6.8 s (50-300 keV). The time-averaged spectrum from T0-2.7 s to T0+5.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.68 +/- 0.12 and the cutoff energy, parameterized as Epeak, is 71 +/- 4 keV. The event fluence (10-1000 keV) in this time interval is (1.64 +/- 0.06)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.9 s in the 10-1000 keV band is 6.7 +/- 0.3 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: 19798 SUBJECT: GRB 160815A: Swift-XRT refined Analysis DATE: 16/08/16 06:08:13 GMT FROM: Phil Evans at U of Leicester V. D'Elia (ASDC), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), A. D'Ai (INAF-IASFPA), A. Maselli (INAF-IASFPA) and C.B. Markwardt report on behalf of the Swift-XRT team: We have analysed 11 ks of XRT data for GRB 160815A (Markwardt et al. GCN Circ. 19794), from 78 s to 34.8 ks after the BAT trigger. The data comprise 8 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 19796). The light curve can be modelled with an initial power-law decay with an index of alpha=6.1 (+1.9, -1.8), followed by a break at T+115 s to an alpha of 0.88 (+/-0.03). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 3.25 (+0.31, -0.26). The best-fitting absorption column is 3.2 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 7.5 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.90 (+/-0.15) and a best-fitting absorption column of 2.6 (+0.7, -0.6) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (5.3 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.6 (+0.7, -0.6) x 10^21 cm^-2 Galactic foreground: 7.5 x 10^20 cm^-2 Excess significance: 5.1 sigma Photon index: 1.90 (+/-0.15) If the light curve continues to decay with a power-law decay index of 0.88, the count rate at T+24 hours will be 0.013 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.9 x 10^-13 (6.7 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00708598. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19799 SUBJECT: GRB 160815A: Swift-BAT refined analysis DATE: 16/08/16 14:26:01 GMT FROM: Takanori Sakamoto at AGU A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), 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 160815A (trigger #708598) (Markwardt, et al., GCN Circ. 19794). The BAT ground-calculated position is RA, Dec = 288.616, 84.298 deg which is RA(J2000) = 19h 14m 27.8s Dec(J2000) = +84d 17' 53.9" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 41%. The mask-weighted light curve shows several overlapping peaks starting at T-7 sec and ending at T+11 sec. Two main pulses peaks at T+0.3 sec and T+2.5 sec. T90 (15-350 keV) is 8.6 +- 1.8 sec (estimated error including systematics). The time-averaged spectrum from T-6.41 to T+5.20 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.96 +- 0.41, and Epeak of 68 +- 16 keV (chi squared 48.11 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.4 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+2.14 sec in the 15-150 keV band is 4.7 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.72 +- 0.09 (chi squared 59.91 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/708598/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19801 SUBJECT: GRB 160815A: Swift/UVOT Detection DATE: 16/08/16 21:53:24 GMT FROM: Mike Siegel at PSU/Swift MOC S.J. LaPorte (PSU) and C. B. Markwardt (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160815A 90 s after the BAT trigger (Markwardt et al., GCN Circ. 19794). We detect a fading source consistent with the XRT position (Beardmore et al. GCN Circ. 19796). Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 90 239 146 18.17+-0.14 white 582 5549 402 >19.72 v 632 5960 274 >17.99 b 557 5344 254 >18.64 u 301 6449 554 >18.85 uvw1 681 6370 432 >18.67 uvm2 656 6165 274 >18.64 uvw2 607 5755 274 >18.70 The magnitude is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.12 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19807 SUBJECT: GRB 160815A: GWAC-F60A upper limit DATE: 16/08/17 07:52:18 GMT FROM: L.P. Xin at NAOC L. P. Xin, Y. J. Xiao, X. M. Meng, J. Y. Wei, E. W. Liang, X. G. Wang, Y. G. Yang, X. M. Lu, L. Huang, X. H. Han , H. B. Cai, Y. L. Qiu, J. Wang, C. Wu, J. S. Deng and H. L. Li report: We observed GRB 160815A (Markwardt et al. GCN 19794) with GWAC-F60A 60cm optical telescope at 17:10:08 UT, Aug. 15th 2016, about 5.41 hours after the burst. The optical afterglow (Marshall et al., GCN 19795; LaPorte et al., GCN 19081) was not detected in our 20*300 sec stacked R-band images down to the 3 sigma limit of about 19.7 mag at the mid time of 6.42 hours after the burst. The brightness was calibrated by USNO B1.0 stars. GWAC-F60A is operated by Guangxi university and NAOC, CAS, at Xinglong observatory, China. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19823 SUBJECT: GRB 160815A: CALET Gamma-Ray Burst Monitor detection DATE: 16/08/19 07:57:27 GMT FROM: Takanori Sakamoto at AGU S. Ricciarini (U of Florence), 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), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), P. S. Marrocchesi (U of Siena) and the CALET collaboration: The long-duration GRB 160815A (Markwardt et al., GCN Circ. 19794; Hamburg et al., GCN Circ. 19797) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 11:45:10.86 on 15 August 2016. The burst signal was seen by the SGM instrument. Because of a problem in one of the ground alert processing computer, the GCN notice was not distributed automatically for this event. The light curve of the SGM shows several two peaks. The whole emission starts at T0 and ends at T+4 sec. The two spikes peak at T+0.5 sec and T+3 sec. The T90 duration measured by the SGM data is 3.6 +- 0.6 sec (40-100 keV). The light curve is available at http://cgbm.calet.jp/cgbm_trigger/flight/1155296575/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.