{
  "bibcode": "2021GCN.29877....1D",
  "body": "James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea\n(PSU) report:\n\nSwift/BAT did not trigger on GRB 210421B (T0: 2021-04-21 10:54:44 UTC,\nFermi/GBM GCN 29870, 29874; INTEGRAL/SPI-ACS trigger 9154).\n\nThe INTEGRAL/SPI-ACS notice, distributed in near real-time triggered\nthe Swift Mission Operations Center operated Gamma-ray Urgent Archiver\nfor Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).\n\nUpon trigger by this notice, GUANO sent a command to the Swift Burst\nAlert Telescope (BAT) to save 90 seconds of BAT event-mode data from\n[-45,+45] seconds around the time of the burst. All the requested\nevent mode data was delivered to the ground.\n\nThe burst is strongly detected in BAT with a duration of ~15 seconds,\nconfirming the long classification correction of Fermi/GBM (GCN\n29874).\nThe burst occurred during a Swift slew.\nThe position of the burst was found with SNR of 9.7 using a novel slew\nimage mosaicing procedure (DeLaunay et al. 2021, in prep.), and so the\npositional uncertainty is not yet well characterized.\n\nThe BAT position is\nRA, Dec = 270.817, 56.828 deg which is\n   RA(J2000)  = 18h 03m 16.08s\n   Dec(J2000) =  56d 49��� 40.8���\nwith an estimated uncertainty of at least 5 arcmin.\n\nThis position is consistent with the Fermi GBM localization (GCN 29870).\n\nXRT and UVOT follow-up has been requested. Results of follow-up\nobservations will be reported in future circulars.\n\nGUANO is a fully autonomous, extremely low latency, spacecraft\ncommanding pipeline designed for targeted recovery of BAT event mode\ndata around the times of compelling astrophysical events to enable\nmore sensitive GRB searches.\n\nA live reporting of Swift/BAT event data recovered by GUANO can be\nfound at: https://www.swift.psu.edu/guano/",
  "circularId": 29877,
  "createdOn": 1619045242000,
  "email": "aaron.tohu@gmail.com",
  "subject": "GRB 210421B: Swift/BAT-GUANO detection and arcminute localization",
  "submitter": "Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>",
  "eventId": "GRB 210421B"
}