//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22433 SUBJECT: GRB 180222A: Swift detection of a burst DATE: 18/02/22 13:37:12 GMT FROM: Scott Barthelmy at NASA/GSFC J. K. Cannizzo (NASA/UMBC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), P. A. Evans (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), Z. Liu (NAOC/U. Leicester), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 13:10:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 180222A (trigger=811235). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 256.571, -36.803, which is RA(J2000) = 17h 06m 17s Dec(J2000) = -36d 48' 08" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single FRED-like peak with a duration of about 25 sec. The peak count rate was ~1400 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 13:11:22.7 UT, 79.2 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 256.54119, -36.80929 which is equivalent to: RA(J2000) = 17h 06m 09.89s Dec(J2000) = -36d 48' 33.4" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 88 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 (6.65 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 7.9 (+11.04/-4.96) x 10^21 cm^-2 (90% confidence). 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 97% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the large, but uncertain, extinction expected. Burst Advocate for this burst is J. K. Cannizzo (cannizzo 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: 22434 SUBJECT: GRB 180222A: A long GRB detected by INTEGRAL DATE: 18/02/22 14:19:25 GMT FROM: Sandro Mereghetti at IASF-Milano/INAF S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo, V.Savchenko (ISDC, Versoix), L. Ducci (IAAT, Germany and ISDC, Versoix) and J.Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report: a gamma ray burst lasting about 20 s has been detected by IBAS in the IBIS/ISGRI data at 13:10:02 UT of February 22, 2018 The refined coordinates (J2000) are: R.A.= 256.5418 deg DEC.= -36.8016 deg with an uncertainty of 1.5 arcmin (90% c.l.). The burst had a peak flux of about 1 counts/cm2/s (20-200 keV, 1-s integration time) and a fluence in the same energy range of about 6e-7 erg/cmq. This burst was also detected by the Swift/BAT (Cannizzo et al., GCN 22433). A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22435 SUBJECT: GRB 180222A: Enhanced Swift-XRT position DATE: 18/02/22 18:01:44 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 2537 s of XRT Photon Counting mode data and 3 UVOT images for GRB 180222A, 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 = 256.54179, -36.81207 which is equivalent to: RA (J2000): 17h 06m 10.03s Dec (J2000): -36d 48' 43.4" with an uncertainty of 6.8 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: 22436 SUBJECT: GRB 180222A: Swift-BAT refined analysis DATE: 18/02/22 21:35:52 GMT FROM: Hans Krimm at NSF/NASA-GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. K. Cannizzo (NASA/UMBC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), 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+423 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180222A (trigger #811235) (Cannizzo, et al., GCN Circ. 22433). The BAT ground-calculated position is RA, Dec = 256.537, -36.819 deg which is RA(J2000) = 17h 06m 08.8s Dec(J2000) = -36d 49' 08.2" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%. The mask-weighted light curve consists of a single FRED pulse beginning at ~T-8 sec, peaking at T+0 sec and decaying to background by T+60 sec. T90 (15-350 keV) is 64.0 +- 22.6 sec (estimated error including systematics). The time-averaged spectrum from -15.1 to 48.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.40 +- 0.21. The fluence in the 15-150 keV band is 7.9 +- 1.0 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+8.44 sec in the 15-150 keV band is 0.4 +- 0.1 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/811235/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22437 SUBJECT: GRB 180222A: Swift-XRT refined Analysis DATE: 18/02/23 01:10:38 GMT FROM: Phil Evans at U of Leicester A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester) and J.K. Cannizzo report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 180222A (Cannizzo et al. GCN Circ. 22433), from 82 s to 24.2 ks after the BAT trigger. The data comprise 54 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 22435). The light curve can be modelled with a power-law decay with a decay index of alpha=2.25 (+0.19, -0.18). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.7 (+0.6, -0.5). The best-fitting absorption column is 1.7 (+0.9, -0.8) x 10^22 cm^-2, in excess of the Galactic value of 6.6 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.4 x 10^-11 (9.2 x 10^-11) erg cm^-2 count^-1. A summary of the WT-mode spectrum is thus: Total column: 1.7 (+0.9, -0.8) x 10^22 cm^-2 Galactic foreground: 6.6 x 10^21 cm^-2 Excess significance: 2.3 sigma Photon index: 1.7 (+0.6, -0.5) If the light curve continues to decay with a power-law decay index of 2.25, the count rate at T+24 hours will be 1.1 x 10^-6 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 x 10^-17 (9.7 x 10^-17) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00811235. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 22439 SUBJECT: GRB 180222A: Swift/UVOT Upper Limits DATE: 18/02/23 20:49:37 GMT FROM: Mike Siegel at PSU/Swift MOC S. A. Sebzda (PSU) and J. K. Cannizzo (NASA/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180222A 83 s after the BAT trigger (Cannizzo et al., GCN Circ. 22433). No optical afterglow consistent with the XRT position (Cannizzo et al. GCN Circ. 22433) 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 83 233 147 >20.6 u_FC 295 545 246 >19.5 white 83 1196 353 >21.6 v 624 1073 58 >18.0 b 551 1171 58 >18.6 u 295 1146 285 >19.7 w1 673 1122 58 >18.0 m2 649 1097 58 >18.0 w2 600 1221 78 >19.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.68 in the direction of the burst (Schlegel et al. 1998).