//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32465 SUBJECT: GRB 220813A: Swift detection of a burst with an optical counterpart DATE: 22/08/13 19:35:48 GMT FROM: David Palmer at LANL M. G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), M. Ferro (INAF-OAB), J.D. Gropp (PSU), A. Melandri (INAF-OAB), K. L. Page (U Leicester), D. M. Palmer (LANL), T. M. Parsotan (GSFC/UMBC/CRESSTII), T. Sbarrato (INAF-OAB) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 19:23:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220813A (trigger=1120270). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 81.501, -32.985 which is RA(J2000) = 05h 26m 00s Dec(J2000) = -32d 59' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peak structure with a duration of about 30 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 19:24:34.2 UT, 90.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 81.53235, -33.01546 which is equivalent to: RA(J2000) = 05h 26m 07.76s Dec(J2000) = -33d 00' 55.7" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 144 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 (2.32 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.7 (+3.14/-2.65) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 100 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 05:26:07.57 = 81.53155 DEC(J2000) = -33:00:58.9 = -33.01636 with a 90%-confidence error radius of about 0.67 arc sec. This position is 4.7 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.61 with a 1-sigma error of about 0.17. No correction has been made for the expected extinction corresponding to E(B-V) of 0.022. Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini AT brera.inaf.it). 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: 32466 SUBJECT: GRB 220813A: Enhanced Swift-XRT position DATE: 22/08/14 02:15:47 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 4997 s of XRT Photon Counting mode data and 11 UVOT images for GRB 220813A, 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 = 81.53144, -33.01688 which is equivalent to: RA (J2000): 05h 26m 7.55s Dec (J2000): -33d 01' 00.8" with an uncertainty of 2.0 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: 32467 SUBJECT: Swift GRB 220813A: Global MASTER-Net observations report DATE: 22/08/14 06:44:23 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 220813A ( M. G. Bernardini et al., GCN 32465) errorbox 40368 sec after notice time and 40414 sec after trigger time at 2022-08-14 06:36:37 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 72 deg. The sun altitude is -58.5 deg. The galactic latitude b = -31 deg., longitude l = 237 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2055501 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 40504 | MASTER-OAFA | C | 180 | 17.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32468 SUBJECT: GRB 220813A: Swift-XRT refined Analysis DATE: 22/08/14 06:47:04 GMT FROM: Phil Evans at U of Leicester J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU) and M.G. Bernardini report on behalf of the Swift-XRT team: We have analysed 8.4 ks of XRT data for GRB 220813A (Bernardini et al. GCN Circ. 32465), from 80 s to 30.0 ks after the BAT trigger. The data comprise 149 s in Windowed Timing (WT) mode (the first 8 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 32466). The late-time light curve (from T0+4.9 ks) can be modelled with a power-law decay with a decay index of alpha=0.98 (+0.15, -0.14). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.53 (+/-0.13). The best-fitting absorption column is 1.37 (+0.29, -0.27) x 10^21 cm^-2, in excess of the Galactic value of 2.3 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.00 (+/-0.13) and a best-fitting absorption column of 4.9 (+2.9, -2.6) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.2 x 10^-11 (3.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 4.9 (+2.9, -2.6) x 10^20 cm^-2 Galactic foreground: 2.3 x 10^20 cm^-2 Excess significance: 1.7 sigma Photon index: 2.00 (+/-0.13) If the light curve continues to decay with a power-law decay index of 0.98, the count rate at T+24 hours will be 9.7 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.1 x 10^-13 (3.5 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/01120270. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32470 SUBJECT: GRB 220813A: Swift/UVOT Detection DATE: 22/08/14 09:55:19 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and M. G. Bernardini (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 220813A 100 s after the BAT trigger (Bernardini et al., GCN Circ. 32465). A source consistent with the XRT position (Osborne et al., GCN Circ. 32466) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 05:26:07.60 = 81.53166 (deg.) Dec (J2000) = -33:00:59.0 = -33.01638 (deg.) with an estimated uncertainty of 0.52 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 100 250 147 19.67 +/- 0.11 v 589 1581 117 >18.3 b 515 1506 97 >19.6 u 258 1652 360 >20.6 w1 638 1630 117 >19.6 m2 613 1605 117 >20.1 w2 564 1556 117 >20.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.022 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32471 SUBJECT: GRB 220813A: VLT optical observations and possible host galaxy DATE: 22/08/14 12:52:42 GMT FROM: Dong Xu at NAOC/CAS H. Fausey (GWU), Z.P. Zhu (NAOC, HUST), P. D'Avanzo (INAF-OAB), D. B. Malesani (Radboud Univ. and DAWN/NBI), L. Izzo (DARK/NBI), D. A. Kann (IAA-CSIC), D. Xu (NAOC) report on behalf of the Stargate collaboration: We observed the field of GRB 220813A (Bernardini et al., GCN 32465) using the ESO VLT/UT3 equipped with the X-shooter acquisition camera. Observations started at 08:06:45 UT on 2022-08-14 (i.e., ~12.73 hr after the BAT trigger) and consisted of 3x60 s, 4x60 s, 3x60 s exposures in the Sloan g-/r-/z- bands, respectively. The previously reported optical afterglow (Bernardini et al., GCN 32465; Kuin & Bernardini, GCN 32470) is marginally detected in the stacked r-band image with r ~ 21.8 mag (AB), and is not detected in g-band and z-band with upper limits of g > 22.1 and z > 19.9, respectively (both AB). In addition, we note that from Legacy Survey there exists a source at coordinates R.A. (J2000) = 05:26:07.5 and Dec.(J2000) = -33:00:59.2, being consistent with the Swift/UVOT position, which has photometric magnitudes of g ~ 24.99, r ~ 24.28 and z ~ 23.76 as well as photometric redshift of z ~ 0.82, which is the likely host galaxy of GRB 220813A. We thank the great support of the ESO VLT staff, in particular Steffen Mieske and Michael Abdul-Masih. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 32472 SUBJECT: Konus-Wind detection of GRB 220813A DATE: 22/08/15 12:02:50 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, A.Lysenko, A. Ridnaya, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 220813A (Swift detection: Bernardini et al., GCN 32465) was detected by Konus-Wind (KW) in the waiting mode. A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a >6 sigma count rate increase in the interval from T0-8.841 s to T0+5.879 s where T0 = T0(BAT) = 19:23:03.577 UT. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB220813A/ Modeling a time-integrated spectrum of the burst (from T0-8.841 s to T0+8.823 s) by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -0.81 (-0.12, + 0.12) and Ep = 242(-17,+23) keV. In the 10 keV -10 MeV band, standard for the KW analysis, the burst fluence is (1.41 ± 0.14)x10^-6 erg/cm^2 and the 2.944 s peak energy flux is (1.30 ± 0.13)x10^-7 erg/cm^2/s. Assuming the likely host galaxy redshift z=0.82 (Fausey et al., GCN 32471) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the burst isotropic energy release E_iso to ~2.7x10^51 erg, the isotropic peak luminosity L_iso to ~8.0x10^50 erg/s, and the rest-frame peak energy of the spectrum Ep,z to ~440 keV. With the obtained estimates, GRB 220813A is a hard-spectrum / low-luminosity outlier in both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB220813A/GRB220813A_rest_frame.pdf All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.