{
  "bibcode": "2023GCN.33315....1R",
  "body": "Gayathri Raman (PSU), Jamie A. Kennea (PSU), James DeLaunay\n(UAlabama), Aaron Tohuvavohu (U Toronto) report:\n\nSwift/BAT did not localize GRB 230209B onboard (T0:\n2023-02-09T22:32:36 UTC, Fermi/GBM GCN 33310, INTEGRAL trig 10198).\n\nThe Fermi and INTEGRAL notices, distributed in near real-time,\ntriggered the Swift Mission Operations Center operated Gamma-ray\nUrgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al.\n2020, ApJ, 900, 1).\n\nUpon trigger by this notice, GUANO sent a command to the Swift Burst\nAlert Telescope (BAT) to save 200 seconds of BAT event-mode data from\n[-50,+150] seconds around the time of the burst. All the requested\nevent mode data was delivered to the ground.\n\nThe BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ,\n941, 169), detects the burst with a sqrt(TS) of 42.1 in a 2.048 s\nanalysis time bin.\nThe burst duration as seen by BAT is ~60 s.\n\nNITRATES results indicate a burst coming from outside the FOV, with\nDeltaLLHOut of -53.\nThe NITRATES best fit OFOV position is consistent with the Fermi/GBM\nlocalization (GCN 33310).\n\nSee Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief\ndescriptions and interpretation of sqrt(TS), DeltaLLHPeak, and\nDeltaLLHOut.\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": 33315,
  "createdOn": 1676075853000,
  "email": "aaron.tohu@gmail.com",
  "subject": "GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV",
  "submitter": "Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>",
  "eventId": "GRB 230209B"
}