//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32060 SUBJECT: GRB 220518A: Swift detection of a burst DATE: 22/05/18 06:47:24 GMT FROM: Kim Page at U.of Leicester J.D. Gropp (PSU), K. L. Page (U Leicester), T. M. Parsotan (GSFC/UMBC/CRESSTII), B. Sbarufatti (PSU) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 06:19:20 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220518A (trigger= 1107050). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 55.369, -47.571 which is RA(J2000) = +03h 41m 29s Dec(J2000) = -47d 34' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). There are currently no BAT light curve data available at this time. The XRT began observing the field at 06:21:27.1 UT, 126.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 55.34297, -47.58392 which is equivalent to: RA(J2000) = 03h 41m 22.31s Dec(J2000) = -47d 35' 02.1" with an uncertainty of 1.9 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 https://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 (9.33 x 10^19 cm^-2, Willingale et al. 2013), with an excess column of 5 (+3.25/-2.72) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 129 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 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.008. Burst Advocate for this burst is J.D. Gropp (jdg44 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: 32061 SUBJECT: Swift GRB 220518A: Global MASTER-Net observations report DATE: 22/05/18 08:36:38 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev (Irkutsk State University, API), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational State University) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 220518A ( J.D. Gropp et al., GCN 32060) errorbox 6501 sec after notice time and 6534 sec after trigger time at 2022-05-18 08:08:15 UT, with upper limit up to 15.6 mag. The observations began at zenith distance = 87 deg. The sun altitude is -40.1 deg. The galactic latitude b = -51 deg., longitude l = 256 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1977169 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 6565 | MASTER-OAFA | C | 60 | 14.3 | 7687 | MASTER-OAFA | C | 180 | 15.3 | 7947 | MASTER-OAFA | C | 60 | 15.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32062 SUBJECT: GRB 220518A: Enhanced Swift-XRT position DATE: 22/05/18 10:12:12 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 1717 s of XRT Photon Counting mode data and 2 UVOT images for GRB 220518A, 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 = 55.34331, -47.58376 which is equivalent to: RA (J2000): 03h 41m 22.39s Dec (J2000): -47d 35' 01.5" with an uncertainty of 2.2 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: 32063 SUBJECT: GRB 220518A: Swift/UVOT Detection DATE: 22/05/18 15:09:29 GMT FROM: Samantha Oates at MSSL S. R. Oates (U.Birmingham) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 220518A 129 s after the BAT trigger (Gropp et al., GCN Circ. 32060). A source consistent with the enhanced XRT position (Beardmore et al. GCN Circ. 32062) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 03:41:22.29 = 55.34289 (deg.) Dec (J2000) = -47:35:00.3 = -47.58342 (deg.) with an estimated uncertainty of 0.55 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 (FC) 129 279 147 20.00 +/- 0.25 white 621 1717 334 20.49 +/- 0.23 v 671 1767 136 >19.0 b 597 1861 131 >20.1 u (FC) 341 591 246 >19.7 u 341 1841 324 >19.9 w1 1103 1296 39 >18.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.008 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32067 SUBJECT: GRB 220518A: Swift-XRT refined Analysis DATE: 22/05/19 00:06:54 GMT FROM: Phil Evans at U of Leicester J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and J.D. Gropp report on behalf of the Swift-XRT team: We have analysed 6.5 ks of XRT data for GRB 220518A (Gropp et al. GCN Circ. 32060), from 133 s to 53.3 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 32062). The late-time light curve (from T0+7.3 ks) can be modelled with a power-law decay with a decay index of alpha=1.3 (+/-0.4). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.85 (+0.15, -0.14). The best-fitting absorption column is 2.7 (+3.1, -1.8) x 10^20 cm^-2, consistent with the Galactic value of 9.3 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 3.5 x 10^-11 (3.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.7 (+3.1, -1.8) x 10^20 cm^-2 Galactic foreground: 9.3 x 10^19 cm^-2 Excess significance: <1.6 sigma Photon index: 1.85 (+0.15, -0.14) If the light curve continues to decay with a power-law decay index of 1.3, the count rate at T+24 hours will be 3.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-13 (1.3 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/01107050. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32069 SUBJECT: GRB 220518A: Swift-BAT refined analysis DATE: 22/05/19 22:19:52 GMT FROM: Tyler Parsotan at UMBC/GSFC/CRESST II S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU), (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 220518A (trigger #1107050) (Gropp et al., GCN 32060). The BAT ground-calculated position is RA, Dec = 55.340, -47.593 deg which is RA(J2000) = 03h 41m 21.6s Dec(J2000) = -47d 35' 36.3" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 51%. The light curve has a peak at the trigger time and potential precursor emission occuring slightly before the BAT trigger time. T90 (15-350 keV) is 12.29 +- 3.07 sec (estimated error including systematics). The time-averaged spectrum from T-8.36 to T+7.58 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.71 +- 0.21. The fluence in the 15-150 keV band is 5.7 +- 0.8 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.07 sec in the 15-150 keV band is 1.8 +- 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/1107050/BA/