//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26021 SUBJECT: GRB 191017B: Swift detection of a burst DATE: 19/10/17 14:55:44 GMT FROM: David Palmer at LANL B. Sbarufatti (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC), M. J. Moss (GWU), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 14:36:06 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 191017B (trigger=929981). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 245.151, -73.561 which is RA(J2000) = 16h 20m 36s Dec(J2000) = -73d 33' 40" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 8 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 14:37:50.7 UT, 103.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 245.1255, -73.5404 which is equivalent to: RA(J2000) = 16h 20m 30.13s Dec(J2000) = -73d 32' 25.3" with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 78 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 (9.84 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3 (+3.00/-2.59) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 301 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 0.11. Burst Advocate for this burst is B. Sbarufatti (bxs60 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/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26022 SUBJECT: GRB 191017B: Enhanced Swift-XRT position DATE: 19/10/17 20:12:56 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 759 s of XRT Photon Counting mode data and 2 UVOT images for GRB 191017B, 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 = 245.12493, -73.54074 which is equivalent to: RA (J2000): 16h 20m 29.98s Dec (J2000): -73d 32' 26.7" with an uncertainty of 1.8 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: 26027 SUBJECT: GRB 191017B: Swift-XRT refined Analysis DATE: 19/10/18 05:32:16 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), D.N. Burrows (PSU), J. D. Gropp (PSU), A. Tohuvavohu (U. Toronto), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester) and B. Sbarufatti report on behalf of the Swift-XRT team: We have analysed 6.1 ks of XRT data for GRB 191017B (Sbarufatti et al. GCN Circ. 26021), from 256 s to 29.2 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 26022). The light curve can be modelled with a power-law decay with a decay index of alpha=0.64 (+/-0.05). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.54 (+0.20, -0.12). The best-fitting absorption column is consistent with the Galactic value of 9.8 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 9.8 (+/-6.9) x 10^20 cm^-2 Galactic foreground: 9.8 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.54 (+0.20, -0.12) If the light curve continues to decay with a power-law decay index of 0.64, the count rate at T+24 hours will be 0.018 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.8 x 10^-13 (8.6 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/00929981. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26029 SUBJECT: GRB 191017B: Swift/UVOT Upper Limits DATE: 19/10/18 14:37:28 GMT FROM: Sam LaPorte at PSU GRB 191017B: Swift/UVOT Upper Limits J. D. Gropp (PSU) and B. Sbarufatti (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 191017B 302 s after the BAT trigger (Sbarufatti et al., GCN Circ. 26021). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 26022) 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 302 452 147 >18.9 white 302 1010 334 >19.1 v 460 4806 255 >18.1 b 558 752 39 >18.3 u 533 727 39 >18.9 w1 509 702 39 >18.2 m2 484 852 39 >18.6 w2 609 4601 235 >20.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.11 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26030 SUBJECT: GRB 191017B: Swift-BAT refined analysis DATE: 19/10/18 23:37:15 GMT FROM: Sibasish Laha at GSFC J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), B. Sbarufatti (PSU), M. Stamatikos (OSU), T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), (i.e. the Swift-BAT team): Using the data set from T-82 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 191017B (trigger #929981) (Sbarufatti et al., GCN Circ. 26021). The BAT ground-calculated position is RA, Dec = 245.131, -73.583 deg which is RA(J2000) = 16h 20m 31.3s Dec(J2000) = -73d 34' 57.7" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 44%. The mask weighted light curve shows a single peak structure with a duration of ~8 sec. The overall structure starts at ~ T-2 sec and lasts till ~ T+6 sec. T90 (15-350 keV) is 5.95 +- 1.28 sec (estimated error including systematics). The time-averaged spectrum from T-1.34 to T+5.59 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.82 +- 0.20. The fluence in the 15-150 keV band is 5.6 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.36 sec in the 15-150 keV band is 1.9 +- 0.3 ph/cm2/sec. 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/929981/BA/