[vsnet-grb-info 26483] GRB 201008A: Swift/BAT-GUANO detection and possible arcminute localization

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28583
SUBJECT: GRB 201008A: Swift/BAT-GUANO detection and possible arcminute localization
DATE:    20/10/08 22:41:45 GMT
FROM:    James DeLaunay at PSU  <jjd330 at psu.edu>

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

Swift/BAT did not trigger on GRB 201008A (T0: 2020-10-08 10:37:36 UTC,
Fermi/GBM Team TRIGGER 623846261).

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 T90 duration of ~2.5 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 13.22. The sqrt(TS) behaves

similarly to SNR.

Using the normal BAT imaging technique, we find the location of the GRB
with an SNR of 4.2.

Since this is a low significance detection near the edge of the coded field
of view there is a chance that this localization may be incorrect.

The BAT ground-calculated position is

RA, Dec = 161.744, 46.101 deg which is

   RA(J2000)  = 10h 46m 58.56s

   Dec(J2000) =  46d 06’ 03.6”

with an uncertainty of 5 arcmin, (radius, sys+stat, 90% containment).

The partial coding was 3.5%.

This position is consistent with the Fermi GBM localization (
https://gcn.gsfc.nasa.gov/other/623846261.fermi) and BALROG localization
(GCN 28577).

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/