//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29701 SUBJECT: GRB 210323B: Swift/BAT-GUANO detection and possible arcminute localization DATE: 21/03/24 02:57:29 GMT FROM: Aaron Tohuvavohu at U Toronto James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie Kennea (PSU) report: Swift/BAT did not trigger on GRB 210323B (T0: 2021-03-23 12:03:33 UTC, Fermi/GBM TRIGGER 638193818). The Fermi/GBM notice, distributed in near real-time triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The burst is detected in BAT with a best fit duration of ~8 seconds. With a maximum likelihood analysis (DeLaunay et al. 2021, in prep.) on the event-mode data we detect a location for the burst with a square root of the test statistic, sqrt(TS), of 11.77. The sqrt(TS) behaves similarly to SNR. This is a low significance detection and it could not be recovered using the normal BAT imaging technique, so there is a chance that this localization may be incorrect. The BAT position is RA, Dec = 259.664, +15.677 deg which is RA(J2000) = 17h 18m 39.36s Dec(J2000) = +15d 40' 37.20" with an estimated uncertainty of 6 arcmin. The partial coding was 10.6% This position is consistent with the Fermi GBM localization. XRT and UVOT follow-up has been requested. Results of follow-up observations will be reported in future circulars. GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29714 SUBJECT: GRB 210323B: Swift ToO observations DATE: 21/03/24 16:48:22 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Swift/BAT GRB 210323B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021426 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Swift/BAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 29908 SUBJECT: GRB 210323B: Swift-XRT observations DATE: 21/04/27 17:32:50 GMT FROM: Aaron Tohuvavohu at U Toronto M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Swift/BAT-GUANO-detected burst GRB 210323B (James DeLaunay et al. GCN Circ. 29701), collecting 10.2 ks of Photon Counting (PC) mode data between T0+100.8 ks and T0+1300 ks. One uncatalogued X-ray source has been detected consistent with being within the Swift/BAT localization, it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 259.6867 = 17:18:44.80 Dec (J2000.0): +15.6339 = +15:38:02.2 Error: 4.6 arcsec (radius, 90% conf.) Count-rate: (1.18 [+0.71, -0.52])e-3 ct s^-1 Distance: 173 arcsec from Swift/BAT position. Seven uncatalogued sources were also detected too far from the GRB position to be likely afterglow candidates. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021426. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30241 SUBJECT: GRB 210323B: Fermi GBM observation DATE: 21/06/16 17:23:38 GMT FROM: Elisabetta Bissaldi at INFN,Bari E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 12:03:33.09 UT on 23 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 210323B (trigger 638193818/ 210323502), which was also detected by the Swift/BAT-GUANO (DeLaunay et al. 2021, GCN 29701). The Fermi GBM Final Real-time Localization is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 10 degrees. The GBM light curve consists of a weak emission episode with a duration (T90) of about 14 s (50-300 keV). The time-averaged spectrum from T0-4.9 s to T0+5.9 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -0.94 +/- 0.26 and the cutoff energy, parameterized as Epeak, is 740 +/- 540 keV. The event fluence (10-1000 keV) in this time interval is (2.1 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-4.5 s in the 10-1000 keV band is 1.1 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"