//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20182 SUBJECT: GRB 161117B: Swift detection of a burst DATE: 16/11/17 10:04:47 GMT FROM: Mike Siegel at PSU/Swift MOC E. Troja (NASA/GSFC/UMCP), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC), P.A. Evans (U Leicester), H. A. Krimm (CRESST/NSF/USRA), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 09:49:43 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 161117B (trigger=722642). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 298.855, -67.707 which is RA(J2000) = 19h 55m 25s Dec(J2000) = -67d 42' 23" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed am initial weak peak near the trigger time followed by stronger emission starting about 100 seconds later. The total duration is about 150 sec. The peak count rate was ~4500 counts/sec (15-350 keV), at ~135 sec after the trigger. The XRT began observing the field at 09:50:58.0 UT, 74.4 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 298.8244, -67.7029 which is equivalent to: RA(J2000) = 19h 55m 17.85s Dec(J2000) = -67d 42' 10.6" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 44 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 (6.49 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.3 (+2.89/-2.47) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 4.69e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 82 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.10. Burst Advocate for this burst is E. Troja (eleonora.troja 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: 20183 SUBJECT: GRB 161117B: LCO optical observations DATE: 16/11/17 11:30:18 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica) on behalf of a large collaboration report: One of the LCO 1-m telescope units in Siding Springs began observing Swift GRB 161117B (Troja et al., GCN 20182) in the SDSS r filter on November 17, 10:28:49 UT (39 minutes since the GRB trigger time). We do not find any object within the XRT error circle down to the following limit: Mid time from GRB Exposure Filter Magnitude (min) (s) ---------------------------------------------------------- 45 5x120 SDSS-R > 21.2 ---------------------------------------------------------- Calibration is done against nearby USNOB-1 stars. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20186 SUBJECT: GRB 161117B: Enhanced Swift-XRT position DATE: 16/11/17 14:13:23 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 787 s of XRT Photon Counting mode data and 1 UVOT images for GRB 161117B, 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 = 298.82508, -67.70256 which is equivalent to: RA (J2000): 19h 55m 18.02s Dec (J2000): -67d 42' 09.2" 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: 20189 SUBJECT: GRB 161117B: Swift-BAT refined analysis DATE: 16/11/17 18:40:10 GMT FROM: Hans Krimm at NSF/NASA-GSFC T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), E. Troja (NASA/GSFC/UMCP), (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 161117B (trigger #722642) (Troja, et al., GCN Circ. 20182). The BAT ground-calculated position is RA, Dec = 298.830, -67.681 deg which is RA(J2000) = 19h 55m 19.1s Dec(J2000) = -67d 40' 51.8" with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 43%. The mask-weighted light curve shows a complex structure. The first set of peaks begins around T-10 sec, peaks at T+2 and fades by T+10 sec. The second set of peaks begins around T+92 sec, peaks at T+102 sec and fades nearly to background by T+115 sec. This is when the third set of peaks begins to rise, which peaks at T+T+135 sec and fades by T+160 sec. All of these peak structures have multiple sub-peaks. T90 (15-350 keV) is 152.51 +- 3.37 sec (estimated error including systematics). The time-averaged spectrum from T-8.32 to T+157.44 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.39 +- 0.28, and Epeak of 37.5 +- 5.5 keV (chi squared 39.62 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 6.0 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+133.80 sec in the 15-150 keV band is 6.0 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.14 +- 0.06 (chi squared 64.42 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/722642/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20191 SUBJECT: GRB 161117B: Swift/UVOT Upper Limits DATE: 16/11/17 23:07:40 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 161117B 84 s after the BAT trigger (Troja et al., GCN Circ. 20182). No optical afterglow consistent with the XRT position (Osborne et al. GCN Circ. 20186) 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 first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 84 234 147 >21.1 u_FC 296 546 246 >20.3 white 84 1026 334 >21.4 v 626 820 39 >18.1 b 552 745 39 >19.6 u 296 720 265 >20.3 w1 676 870 39 >18.9 m2 651 844 39 >19.9 w2 602 1050 57 >19.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.10 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 20198 SUBJECT: GRB 161117B: Swift-XRT refined Analysis DATE: 16/11/20 13:16:42 GMT FROM: Antonino D'Ai at IASF-PA V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift-XRT team: We have analysed 5.9 ks of XRT data for GRB 161117B (Troja et al. GCN Circ. 20182), from 65 s to 206.7 ks after the BAT trigger. The data comprise 178 s in Windowed Timing (WT) mode (the first 7 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 20186). The light curve shows an initial bright flare that is part of the prompt GRB emission. At T+95.1 s the decay can be modelled with a power-law of index alpha of 0.43 (+0.09, -0.07) before breaking at T+101 ks to a final decay with index alpha=6.7 (+1.3, -5.2). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.10 (+/-0.05). The best-fitting absorption column is 3.8 (+/-0.4) x 10^21 cm^-2, in excess of the Galactic value of 6.5 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.98 (+0.24, -0.23) and a best-fitting absorption column of 5.3 (+1.5, -1.3) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.2 x 10^-11 (6.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.3 (+1.5, -1.3) x 10^21 cm^-2 Galactic foreground: 6.5 x 10^20 cm^-2 Excess significance: 5.9 sigma Photon index: 1.98 (+0.24, -0.23) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00722642. This circular is an official product of the Swift-XRT team.