GRB 230822A

The Fermi GBM team reports the detection of a likely LONG GRB

At 23:48:54 UT on 22 Aug 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230822A (trigger 714440939.403512 / 230822992).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 143.4, Dec = 38.0 (J2000 degrees, equivalent to J2000 09h 33m, 38d 00'), with a statistical uncertainty of 18.4 degrees.

The angle from the Fermi LAT boresight is 78.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230822992/quicklook/glg_skymap_all_bn230822992.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230822992/quicklook/glg_healpix_all_bn230822992.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230822992/quicklook/glg_lc_medres34_bn230822992.gif

James DeLaunay (UAlabama), Gayathri Raman (PSU), Samuele Ronchini (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:

Swift/BAT did not localize GRB 230822A onboard (T0: 2023-08-22T23:48:54.40 UTC, Fermi GBM Trig 714440939, GCN 34521
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 ). 

The Fermi 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 BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), detects the burst with a sqrt(TS) of 9.7 in a 1.024 s analysis time bin, starting at T0 - 1.792 s.

NITRATES results, independently, are ambiguous with respect to whether this burst originates from in or outside the BAT coded FOV, with a DeltaLLHOut of 7.7.

See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.

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/

S. Lesage (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 23:48:54 UT on 22 August 2023, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 230822A (trigger 714440939/230822992).
which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2023, GCN 34529
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 ).
The Fermi GBM Final Real-Time Localization was reported previously (Fermi GBM Team 2023, GCN 34521
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 ).

The angle from the Fermi LAT boresight is 78 degrees.

The GBM light curve consists of a single weak emission episode with a duration (T90)
of about 0.9 s (50-300 keV). The time-averaged spectrum
from T0-0.448 to T0 s is best fit by
a simple power law function with index -1.3 +/- 0.2.

The event fluence (10-1000 keV) in this time interval is
(5.7 +/- 2.6)E-08 erg/cm^2. The 64-ms peak photon flux measured
starting from T0-1.7 s in the 10-1000 keV band is 2.2 +/- 0.9 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"