GRB 221023A

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

The Gamma-Ray Imaging Detector (GRID) of AGILE detected gamma-ray
transient emission consistent with the long GRB 221023A reported
by AGILE/MCAL (GCN #32825
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 ) at T0 = 2022-10-23 20:41:34 s (UTC), also
detected by Fermi/GBM (GCN #32826
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 , #32845
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 ), Fermi/LAT (GCN #82831
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 )
and Konus-Wind (GCN #32849
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 ).
A refined AGILE/GRID data analysis in the energy range 30 MeV - 10 GeV
shows a detection with a statistical significance of about 4.3 sigma
overa time integration of 50 s starting at the T0 of GRB 221023A,
at a sky position with Galactic coordinates l=28 deg, b=53 deg, with
and an error radius of 4 deg (90% statistical + systematic error;
R.A.= 232 deg, Decl.= 19 deg (J2000)).
The GRID error circle includes the LAT position.
During the 120s integration, we detected a total of 22 events (11
background events estimated through a Li&Ma analysis), 16 events at
energies above 100 MeV, and 2 events above 1 GeV.

These measurements were obtained with AGILE observing a large portion
of the sky in spinning mode. Additional analysis of AGILE data is in
progress.

A.Ridnaia, D. Frederiks, A.Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 221023A
(AGILE detection: Ursi et al., GCN 32825
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 ;
Fermi-GBM observation: Fermi GBM team, GCN 32826
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 ;
Dunwoody et al., GCN 32845
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 ;
Fermi-LAT detection: Pillera et al., GCN 32831
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 )
triggered Konus-Wind at T0=74492.216 s UT (20:41:32.216).

The burst light curve shows a multipeaked structure,
which starts at ~T0-0.5 s and has a total duration of ~145.9 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB221023_T74492/

As observed by Konus-Wind, the burst
had a fluence of 6.60(-0.35,+0.35)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+18.928 s,
of 3.84(-0.52,+0.52)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+149.248 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.05(-0.03,+0.03),
the high energy photon index beta = -2.27(-0.17,+0.13),
the peak energy Ep = 760(-64,+68) keV
(chi2 = 128/98 dof).

The spectrum near the maximum count rate
(measured from T0+18.688 to T0+19.200 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.66(-0.12,+0.15),
the high energy photon index beta = -2.32(-0.41,+0.22),
the peak energy Ep = 707(-147,+184) keV
(chi2 = 47/55 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.

R. Dunwoody (UCD), J. Mangan (UCD) and C. Meegan (UAH), report on behalf of
the Fermi GBM Team:

"At 20:41:34.92 UT on 23 October 2022, the Fermi Gamma-ray Burst Monitor
(GBM) triggered and located GRB 221023A (trigger 688250499 / 221023862),
this localisation was consistent with the Fermi LAT (GCN 32813
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 ). This event
was also observed by AGILE (GCN 32825
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 ).

The angle from the Fermi LAT boresight is 48 degrees.

The GBM light curve shows one bright peak with a duration (T90) of about 39
s (50-300 keV). The time-averaged spectrum from T0-2 to T0+58 s is best fit
by a Band function with Epeak = 898 +/- 15 keV, alpha = -1.1 +/- 0.004, and
beta = -2.5 +/- 0.03. It is fit equally well with a power law function with
an exponential high-energy cutoff. The power law index is -1.08 +/- 0.003
and the cutoff energy, parameterized as Epeak, is 997 +/- 14 keV.

The event fluence (10-1000 keV) in this time interval is 0.001 +/-
4.350E-06 erg/cm2. The 1-sec peak photon flux measured starting from T0+20
s in the 10-1000 keV band is 60.9 +/- 0.4 ph/s/cm2.

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/"

GRB 221023A: Fermi-LAT detection

Pillera R. (Politecnico and INFN Bari), Cutini S. (INFN Perugia), Maheso 
D. (Johannesburg Univ.),
Cheung C. C. (Naval Research Laboratory), Bissaldi E. (Politecnico and 
INFN Bari),
Di Lalla N. (Stanford Univ.) and Khalil T. (Johannesburg Univ.) report 
on behalf of the Fermi-LAT team:

At 20:41:34.92 on October, 23, 2022 Fermi-LAT detected high-energy 
emission
from GRB 221023A, which was reported by AGILE (Ursi et al. GCN 32825
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 ) 
and GBM (GBM team 32826).


The best LAT on-ground location is found to be

RA, Dec =  230.30, 15.01 (J2000)

with an error radius of 0.04 deg (90 % containment, statistical error 
only).
This was 48 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event 
rate that is spatially
and temporally correlated with the trigger with high significance.


  The 100 MeV - 1 GeV photon flux in the time interval 0-1600 s after
the GBM trigger is (7.0 +/- 0.3)E-05 ph/cm2/s.
The estimated photon index above 100 MeV is -2.25 +/- 0.05.
The highest-energy photon is a 17 GeV event with 99% probability
which is observed 576 seconds after the GBM trigger.

A Swift ToO has been requested for this burst.


The Fermi-LAT point of contact for this burst is
Dimakatso Jeannett Maheso (d.j.maheso@gmail.com).

The Fermi-LAT is a pair conversion telescope designed to
cover the energy band from 20 MeV to greater than 300 GeV.
It is the product of an international collaboration
between NASA and DOE in the U.S. and many scientific
institutions across France, Italy, Japan and Sweden.

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

At 20:41:34.92 UT on 23 October 2022, the Fermi Gamma-ray Burst Monitor
(GBM) triggered and located GRB 221023A (trigger 688250499 / 221023862).

The on-ground calculated location, using the Fermi GBM trigger data, is RA
= 232.3, Dec = 11.8 (J2000 degrees, equivalent to J2000 15h 29m, 11d 48'),
with a statistical uncertainty of 1 degree.

The angle from the Fermi LAT boresight is 52 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn221023862/quicklook/glg_skymap_all_221023862.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/bn221023862/quicklook/glg_healpix_all_bn221023862.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn221023862/quicklook/glg_lc_medres34_bn221023862.gif

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

The AGILE satellite detected a burst at T0 = 2022-10-23 20:41:34 s (UTC).
The burst is clearly visible in the AGILE scientific ratemeters of the
MiniCALorimeter (MCAL; 0.4-100 MeV) and AntiCoincidence (AC; 50-200 keV)
detectors. The event lasted about 35 s and it released a total number of
115660 counts in the MCAL detector (above a background rate of 1120 Hz),
and 251030 counts in the AC detector (above a background rate of 3010 Hz).
The AGILE ratemeters light curves can be found at
http://www.agilescienceapp.it/notices/GRB221023A_AGILE_RM.png .

The event also triggered a partial high time resolution MCAL data
acquisition, from T0+23.34 s to T0+33.35 s (UTC), and released 18196 counts
in the detector, above a background rate of 590 Hz. The MCAL light curve
can be found at
http://www.agilescienceapp.it/notices/GRB221023A_080618_593642494.000000.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.