//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26279 SUBJECT: GRB 191123A: Swift detection of a burst with an optical counterpart DATE: 19/11/23 11:05:32 GMT FROM: Aaron Tohuvavohu at U Toronto A. Tohuvavohu (U Toronto), J.D. Gropp (PSU), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 10:38:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 191123A (trigger=939079). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 215.261, +22.842 which is RA(J2000) = 14h 21m 03s Dec(J2000) = +22d 50' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 150 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 10:39:54.1 UT, 69.8 seconds after the BAT trigger. The position determined from promptly downlinked data differs significantly from the on-board position, suggesting that the XRT may have centroided on a cosmic ray; the initial XRT position notice should be treated with caution. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 215.2619, 22.8600 which is equivalent to: RA(J2000) = 14h 21m 02.87s Dec(J2000) = +22d 51' 36.0" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 64 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 (3.01 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.9 (+2.28/-2.01) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 78 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 14:21:02.87 = 215.26196 DEC(J2000) = +22:51:36.3 = 22.86008 with a 90%-confidence error radius of about 0.75 arc sec. This position is 9.7 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.13 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04. Burst Advocate for this burst is A. Tohuvavohu (aaronb AT swift.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: 26282 SUBJECT: GRB 191123A: Swift/UVOT detection DATE: 19/11/23 16:12:05 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and A. Tohuvavohu (U Toronto) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 191123A 78 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 26279). A candidate optical afterglow was 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 78 228 147 18.26+-0.07 u_FC 290 540 246 >19.89 white 869 1019 147 19.28+-0.13 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26283 SUBJECT: GRB 191123A: iTelescope optical upper limits DATE: 19/11/23 16:55:37 GMT FROM: Filipp Dmitrievich Romanov at Amateur astronomer I observed the field of GRB 191123A (Tohuvavohu et al., GCN Circular 26279) with remote telescope T21 (0.43-m f/6.8 reflector + CCD + f/4.5 focal reducer) of iTelescope.Net in New Mexico Observatory. Two images with a luminance filter and with 120 seconds exposure time were obtained on 2019-11-23. Average time of images: 12:13:54 UT (5710 seconds after trigger; Binx1) and 12:16:38 UT (5874 seconds after trigger; Binx2). I did not detect any optical transients (magnitude limit of about 19.0 G from Gaia DR2 catalogue). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26284 SUBJECT: GRB 191123A: Enhanced Swift-XRT position DATE: 19/11/23 18:35:33 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 1802 s of XRT Photon Counting mode data and 1 UVOT images for GRB 191123A, 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 = 215.26186, +22.85991 which is equivalent to: RA (J2000): 14h 21m 2.85s Dec (J2000): +22d 51' 35.7" 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: 26285 SUBJECT: GRB 191123A: Swift-XRT refined Analysis DATE: 19/11/23 20:52:37 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and A. Tohuvavohu report on behalf of the Swift-XRT team: We have analysed 6.2 ks of XRT data for GRB 191123A (Tohuvavohu et al. GCN Circ. 26279), from 76 s to 18.5 ks after the BAT trigger. The data comprise 540 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 26284). The late-time light curve (from T0+5.6 ks) can be modelled with a power-law decay with a decay index of alpha=1.00 (+/-0.15). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.52 (+/-0.05). The best-fitting absorption column is 6.7 (+1.6, -1.5) x 10^20 cm^-2, in excess of the Galactic value of 3.0 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.98 (+0.12, -0.11) and a best-fitting absorption column of 4.8 (+2.6, -1.8) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.8 (+2.6, -1.8) x 10^20 cm^-2 Galactic foreground: 3.0 x 10^20 cm^-2 Excess significance: <1.6 sigma Photon index: 1.98 (+0.12, -0.11) If the light curve continues to decay with a power-law decay index of 1.00, the count rate at T+24 hours will be 0.022 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.2 x 10^-13 (8.1 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/00939079. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26286 SUBJECT: GRB 191123A: Swift-BAT refined analysis DATE: 19/11/23 22:52:53 GMT FROM: Hans Krimm at NSF/NASA-GSFC S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), A. Tohuvavohu (U Toronto), 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 191123A (trigger #939079) (Tohuvavohu, et al., GCN Circ. 26279). The BAT ground-calculated position is RA, Dec = 215.289, 22.823 deg which is RA(J2000) = 14h 21m 09.3s Dec(J2000) = +22d 49' 23.5" with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 85%. The mask-weighted light curve shows a pair of pulses, each with some sub- structure. The first starts at ~T-10 sec, peaks at T+0 and decays by T+40 sec. The second pulse starts at T+110 sec, peaks soon afterward and decays by T+180 sec. T90 (15-350 keV) is 275.1 +- 102.4 sec (estimated error including systematics). The time-averaged spectrum from -2.1 to 288.1 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.67 +- 0.25. The fluence in the 15-150 keV band is 1.2 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+111.77 sec in the 15-150 keV band is 1.2 +- 0.2 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/939079/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 26287 SUBJECT: GRB 191123A: Swift/UVOT further analysis DATE: 19/11/24 00:57:25 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and A. Tohuvavohu (U. Toronto) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 191123A 78 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 26279). A source consistent with the XRT position (Goad et al. GCN Circ. 26284) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 14:21:02.88 = 215.26200 (deg.) Dec (J2000) = +22:51:36.1 = 22.86002 (deg.) with an estimated uncertainty of 0.44 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits 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 78 228 147 18.25 +/- 0.05 v 620 2111 175 18.28 +/- 0.19 b 546 1168 58 19.18 +/- 0.25 u 290 6376 501 >20.4 w1 669 6171 372 >19.9 m2 1074 5966 216 >19.8 w2 595 12186 944 >20.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998).