GRB 220423A

A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the MGNS/BepiColombo team,

J. Benkhoff on behalf of the BepiColombo team,

D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,

E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, report:

The long-duration GRB 220423A
(AGILE detection: Ursi et al., GCN Circ. 31938
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 ;
Swift/BAT-GUANO detection: Raman et al., GCN Circ. 31943
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 ;
VZLUSAT-2 detection: Ripa et al., GCN Circ. 31965
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 )
was detected by CALET (CGBM), INTEGRAL (SPI-ACS), Konus-Wind,
Swift (BAT), AGILE (MCAL, SA, AC), BepiColombo (MGNS), and VZLUSAT-2
at about 51251 s UT (14:14:11).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
    20.784 (01h 23m 08s) +22.205 (+22d 12' 18")
  Corners:
    19.674 (01h 18m 42s) +21.578 (+21d 34' 40")
    21.136 (01h 24m 33s) +22.784 (+22d 47' 02")
    21.890 (01h 27m 34s) +22.712 (+22d 42' 43")
    20.459 (01h 21m 50s) +21.615 (+21d 36' 56")
  ---------------------------------------------
The error box area is 3047 sq. arcmin, and its maximum
dimension is 2.3 deg (the minimum one is 29 arcmin).
The Sun distance was 13 deg.

This box may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB220423_T51247/IPN

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.

J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), M. Ohno (Hiroshima 
U.),�� N. Werner�� (Masaryk U.),�� L. Meszaros (Konkoly Observatory), H. 
Takahashi (Hiroshima U.), B. Csak (Konkoly Observatory), M. Topinka, F. 
Munz, F. Hroch (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov 
(Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research 
Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei 
(Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. 
Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly 
Observatory),�� T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. 
Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, 
J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU)�� -- the 
VZLUSAT-2/GRB payload collaboration.

A long-duration GRB 220423A (AGILE/MCAL detection: Ursi et al., GCN 
Circ. 31938
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 , Happy Birthday to AGILE!; Swift/BAT detection: Raman et 
al., GCN Circ. 31943
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 ; CALET/CGMB detection: trig. #1334758343; 
INTEGRAL/SPI-ACS detection: trig. #9870; KONUS-Wind detection: trig. 
time 2022-04-23 14:14:07.818 UT) was detected by both GRB detector units 
on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by GRB detector units no. 0 and no. 
1. The 28 sigma detection significance was confirmed at each detector at 
2022-04-23 14:14:14 UTC. The GRB has the T90 duration of 37 s.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB220423A_GCN_VZLUSAT2.pdf

GRB detectors on VZLUSAT-2 are a demonstration payload for a future 
CubeSats constellation (Werner et al. Proc. SPIE 2018). Two GRB modules 
of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 
75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the 
energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 
January 13 from Cape Canaveral.

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

Swift/BAT did not localize GRB 220423A onboard (T0: 2022-04-23T14:14:10
UTC, CALET trig #1334758343, INTEGRAL/SPI-ACS trig #9870, AGILE GCN 31938
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 ).

Happy Birthday AGILE!

The CALET and INTEGRAL notices, 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 92 seconds of BAT event-mode data from [-46,+46]
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 139 in a 8.192 s
analysis time bin.

The burst episode as seen by BAT is ~20s long.

NITRATES results strongly indicate a burst coming from outside the coded
FoV, with DeltaLLHOut of -734.

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/

M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo,
C. Casentini, Y. Evangelista, E. Menegoni, L. Foffano, G. Piano, A. Ursi
(INAF/IAPS), F. Lucarelli, C. Pittori, F. Verrecchia (SSDC, and INAF/OAR),
A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N. Parmiggiani
(INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen University),
M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ.
Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report on behalf of
the AGILE Team:

We notice that today, April 23rd 2022, is the 15th anniversary of the AGILE
launch. The AGILE instrument has been flawlessly operating in orbit since
then. We take this opportunity to thank ASI, the AGILE scientific Team and
the ground segment team for their committment to the excellence of the
mission.

A. Ursi (INAF/IAPS), C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), M.
Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C.
Casentini, Y. Evangelista, E. Menegoni, L. Foffano, G. Piano (INAF/IAPS),
F. Lucarelli (SSDC, and INAF/OAR), A. Bulgarelli, A. Di Piano, V. Fioretti,
F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi
(INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois
(INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ. Trieste and INFN
Trieste), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team:

On its 15th birthday, the AGILE satellite detected the long GRB 220423A at
T0 = 2022-04-23 14:14:14 (UTC), reported by INTEGRAL SPI-ACS (trigger
no.9870) and CALET (trigger no.1334758343).

The burst is clearly visible in the AGILE scientific ratemeters of the
SuperAGILE (SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and
AntiCoincidence (AC; 50-200 keV) detectors. The event lasted about 20 s and
it released a total number of 2150 counts in the SA detector (above a
background rate of 75 Hz), 36645 counts in the MCAL detector (above a
background rate of 1410 Hz), and 81820 counts in the AC detector (above a
background rate of 3220 Hz). The AGILE ratemeter light curves can be found
at http://www.agilescienceapp.it/notices/GRB220423A_AGILE_RM.png .

Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.