//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23364 SUBJECT: GRB 181022A: Swift detection of a burst DATE: 18/10/22 17:53:32 GMT FROM: Scott Barthelmy at NASA/GSFC F. E. Marshall (NASA/GSFC), S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), J.D. Gropp (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA), S. J. LaPorte (PSU), M. J. Moss (George Washington University), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 17:30:13 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 181022A (trigger=868312). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 56.795, -29.332, which is RA(J2000) = 03h 47m 11s Dec(J2000) = -29d 19' 55" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 10 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~3 sec after the trigger. The XRT began observing the field at 17:31:49.9 UT, 96.8 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 56.7920, -29.3797 which is equivalent to: RA(J2000) = 03h 47m 10.09s Dec(J2000) = -29d 22' 46.8" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 171 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 (8.80 x 10^19 cm^-2, Willingale et al. 2013), with an excess column of 4.1 (+3.17/-2.70) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 97 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 none of the XRT error circle. 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 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01. This source lies within the current (Sector 4) field-of-view of TESS camera 2. Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.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: 23365 SUBJECT: GRB 181022A: Swift-BAT refined analysis DATE: 18/10/23 02:14:38 GMT FROM: Amy Lien at GSFC M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+876 sec from the recent telemetry downlink, we report further analysis of BAT GRB 181022A (trigger #868312) (Marshall et al., GCN Circ. 23364). The BAT ground-calculated position is RA, Dec = 56.808, -29.374 deg which is RA(J2000) = 03h 47m 13.9s Dec(J2000) = -29d 22' 26.5" with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a weak pulse that starts at ~T-2 s and ends at ~T+6 s. T90 (15-350 keV) is 6.74 +- 2.30 sec (estimated error including systematics). The time-averaged spectrum from T-1.65 to T+5.65 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.78 +- 0.41. The fluence in the 15-150 keV band is 1.9 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+4.40 sec in the 15-150 keV band is 0.4 +- 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/868312/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23367 SUBJECT: GRB 181022A: Swift/UVOT Upper Limits DATE: 18/10/23 03:30:07 GMT FROM: Sam LaPorte at PSU GRB 181022A: Swift/UVOT Upper Limits S. J. LaPorte (PSU) and F. E. Marshall (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 181022A 78 s after the BAT trigger (Marshall et al., GCN Circ. 23364). No optical afterglow consistent with the XRT position (Marshall et al. GCN Circ. 23364) 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 u_FC 98 347 246 >20.5 v 78 4922 288 >19.8 u 98 5429 503 >20.4 w1 661 5332 274 >20.1 m2 4927 5127 197 >20.2 w2 356 4717 442 >20.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23370 SUBJECT: GRB 181022A: LCO Sutherland observations DATE: 18/10/23 10:10:06 GMT FROM: Renato Martone at Universita' di Ferrara R. Martone, C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara, D. Morris (U. of Virgin Islands) on behalf of a large collaboration report: We observed Swift GRB 181022A (Marshall et al., GCN Circ. 23364) with the LCO 1-m unit at Sutherland on October 22, from 22:20 to 22:51 UT (about 5 hours from the GRB trigger time) with the SDSS i' filter. Within the enhanced Swift-XRT error circle (Marshall et al. GCN Circ. 23364) we do not detect any source down to i’>19.0 mag from a 10x120s exposure at a mid time of about 5.05 hours after the GRB trigger time, as calibrated against nearby USNOB1 objects. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23371 SUBJECT: GRB 181022A: GROND upper limits DATE: 18/10/23 12:07:26 GMT FROM: Patricia Schady at Swift P. Schady (Univ. of Bath) and J. Bolmer (MPE, Garching) report: We observed the field of GRB 181022A (Swift trigger 868312; Marshall et al., GCN #23364) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 01:53 UT on 2018-10-23, 8.4 hrs after the GRB trigger. They were performed at an average seeing of 1.4" and average airmass of 1.8. Based on a total of 16 mins integration time, we do not detect a source within the Swift-XRT error circle reported by Marshall et al. (GCN #868312) down to the following 3 sigma AB magnitudes: g' > 22.8 mag r' > 22.9 mag i' > 22.7 mag z' > 22.5 mag J > 21.3 mag H > 20.8 mag K > 18.9 mag The given limits are derived based on calibrating the images against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.01 in the direction of the burst (Schlafly & Finkbeiner 2011). We thank Markus Rabus for the excellend support from La Silla. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23372 SUBJECT: GRB 181022A: MITSuME Akeno optical upper limits DATE: 18/10/23 15:22:37 GMT FROM: Yutaro Tachibana at Tokyo Tech K. Iida, Y. Tachibana, R. Itoh, K. L. Murata, S. Harita, K. Morita, K. Shiraishi, M. Niwano, R. Adachi, M. Oeda, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We searched for the optical counterpart of GRB 181022A (F. E. Marshall et al., GCN Circular #23364) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2018-09-05 17:32:02.95 UT. We did not find any point source at the enhanced position of the XRT error circle (F. E. Marshall et al., GCN Circular #23364) in all three bands. We obtained following 3-sigma upper limits for the magnitudes. T0+[min] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------- 109.95 18:29:22 420 >18.4 >18.2 >17.7 ------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC catalog for flux calibration. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 23374 SUBJECT: GRB 181022A: Swift-XRT refined Analysis DATE: 18/10/23 17:54:03 GMT FROM: Phil Evans at U of Leicester A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), A. Tohuvavohu (PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), V. D'Elia (ASDC) and F.E. Marshall report on behalf of the Swift-XRT team: We have analysed 2.0 ks of XRT data for GRB 181022A (Marshall et al. GCN Circ. 23364), from 106 s to 5.4 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The best available XRT position (using the promptly downlinked event data, the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) is RA, Dec = 56.7920, -29.3798 which is equivalent to: RA (J2000): 03 47 10.09 Dec(J2000): -29 22 47.2 with an uncertainty of 2.1 arcsec (radius, 90% confidence). The light curve can be modelled with a power-law decay with a decay index of alpha=1.73 (+/-0.24). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.7 (+/-0.5). The best-fitting absorption column is 2.9 (+2.9, -1.9) x 10^21 cm^-2, in excess of the Galactic value of 8.8 x 10^19 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 (5.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.9 (+2.9, -1.9) x 10^21 cm^-2 Galactic foreground: 8.8 x 10^19 cm^-2 Excess significance: 2.5 sigma Photon index: 1.7 (+/-0.5) If the light curve continues to decay with a power-law decay index of 1.73, the count rate at T+24 hours will be 1.2 x 10^-5 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.4 x 10^-16 (7.1 x 10^-16) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00868312. This circular is an official product of the Swift-XRT team.