[vsnet-grb-info 25913] GRB 200623A: Swift/BAT-GUANO detection and arcminute localization of a short GRB

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28013
SUBJECT: GRB 200623A: Swift/BAT-GUANO detection and arcminute localization of a short GRB
DATE:    20/06/23 13:18:09 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu at gmail.com>

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie Kennea
(PSU), and Peter Veres (UAH) report:

Swift/BAT did not trigger on GRB 2006023A (T0: 2020-06-23 03:18:00
UTC, Fermi/GBM Team GCN 28011).

The Fermi/GBM notice, distributed at T0+24 seconds triggered the Swift
Mission Operations Center operated Gamma-ray Urgent Archiver for Novel
Opportunities (GUANO; Tohuvavohu et al. 2020, arXiv: 2005.01751). Upon
trigger by these notices, 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.

In a ground analysis of the data, we detect the burst in the full
detector-summed rates (no localization information) with an SNR of
~12.
The detected duration is ~0.2 seconds.

With a maximum likelihood analysis (DeLaunay et al. 2020, 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 9.8. The sqrt(TS) behaves
similarly to SNR.
Using the normal BAT imaging technique, we find an SNR of 6.4 at the
same location.

The BAT ground-calculated position is
RA, Dec = 242.0952, +53.4678 deg which is
   RA(J2000)  = 16h 8m 22.8s
   Dec(J2000) =  +51d 28’ 4”
with an uncertainty of 4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67.19%.

This position is consistent with the Fermi GBM localization (GCN
28011), falling on the 58% containment contour.

XRT and UVOT follow-up has been triggered. 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/