GRB 220708B: Swift/BAT-GUANO arcminute localization
Abstract
Swift/BAT did not localize GRB 220708B onboard (T0: 2022-07-08T02:06:67 UTC, CALET trig #1341281218). The CALET 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 90 seconds of BAT event-mode data from [-45,+45] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu, arXiv:2111.01769), detects the burst in a 4.096 s analysis time bin with a sqrt(TS) of 41.4. The duration of the burst as seen by BAT is ~7 seconds. A confident arcminute localization is found with DeltaLLHOut of 150 and a DeltaLLHPeak of 68. See Section 9.1 and Figure 20 in the NITRATES paper for brief descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut. The BAT position is RA, Dec = 248.652, 36.338 deg which is RA(J2000) = 16h 34m 36.48s Dec(J2000) = +36d 20' 16.8″ with an estimated uncertainty of 5 arcmin. 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/
- Publication:
-
GRB Coordinates Network
- Pub Date:
- July 2022
- Bibcode:
- 2022GCN.32345....1T