GRB 220606A

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

At 00:35:39 UT on 6 Jun 2022, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 220606A (trigger 676168544.281518 / 220606025).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 258.2, Dec = -26.0 (J2000 degrees, equivalent to J2000 17h 12m, -26d 00'), with a statistical uncertainty of 15.6 degrees.

The angle from the Fermi LAT boresight is 94.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220606025/quicklook/glg_skymap_all_bn220606025.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220606025/quicklook/glg_healpix_all_bn220606025.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220606025/quicklook/glg_lc_medres34_bn220606025.gif

James DeLaunay (UAlabama), Aaron Tohuvavohu (U Toronto),  Gayathri
Raman (PSU), Jamie A. Kennea (PSU), report:

Swift/BAT did not localize GRB 220606A onboard (T0: 2022-02-03T21:15:39.8
 UTC, Fermi/GBM GCN 32164
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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, 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,
arXiv:2111.01769
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 ), detects the burst with a sqrt(TS) of 9.8 in a 4.096
s analysis time bin.

NITRATES results, independently, are ambiguous with respect to whether
this burst originates from in or outside the BAT FOV, with a
borderline DeltaLLHOut of 5.7 and no specific location in the FOV
preferred.

Independent spectral and/or fluence measurements of this burst from
other instruments could help determine the preferred spatial origin.

See Section 9.1 and Figure 20 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/

B. Hristov (UAH) and C. Meegan (UAH)

report on behalf of the Fermi GBM Team:


"At 00:35:39.28 UT on 06 June 2022, the Fermi Gamma-Ray Burst Monitor

(GBM) triggered and located GRB 220606A (trigger 676168544 / 220606025,

GCN 32164
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 ), which was also detected by the Swift/BAT-GUANO

(A. Tohuvavohu et al. 2022, GCN 32171
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 ).


The GBM light curve consists of multiple peaks with a duration (T90)

of about 19.7 +/- 1.6 s (50-300 keV).


The time-averaged spectrum from T0-2.560 s to T0+17.664 s is well fit

by a simple power law with index = -1.37 +/- 0.03.


The event fluence (10-1000 keV) in this time interval is

(2.88 +/- 0.17)E-6 erg/cm^2. The 1-sec peak photon flux measured

starting from T0-0.64 s in the 10-1000 keV band is

1.6 +/- 0.2 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/"