GRB 200920B

A. Ursi (INAF/IAPS), F. Verrecchia (SSDC, and INAF/OAR), M. Tavani
(INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C.
Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli, C. Pittori
(SSDC, and INAF/OAR), A. Bulgarelli, 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:

The AGILE Mini-CALorimeter (MCAL) detected the short GRB 200920B at T0 =
2020-09-20 19:56:59.52 +/- 0.01 s (UTC), detected also by Fermi/GBM
(trigger 622324624 / 200920651).

The event lasted about 0.42 s and released a total number of ~505 counts in
the detector (in the 0.4-100 MeV energy range), above an average background
rate of 540 Hz.

The time-integrated spectrum of the burst can be fitted in the energy range
0.4-5 MeV with a single power-law with ph.ind. = 2.41 -0.30/+0.37,
resulting in a reduced chi-squared of 1.14 (36 d.o.f.) and a fluence of
3.46e-7 ergs/cm^2 (90% confidence level), in the same energy range.

The MCAL light curve can be found at
http://www.agilescienceapp.it/notices/GRB200920B_069656_527716619.529166.png
.

The event is also clearly visible in the AGILE scientific ratemeters of the
SuperAGILE (SA; 18-60 keV), MCAL (0.4-100 MeV), and AntiCoincidence (50-200
keV) detectors. Their light curves can be found at:
http://www.agilescienceapp.it/notices/GRB200920B_AGILE_RM.png .

The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the
energy range 0.4-100 MeV. Additional analysis of AGILE data is in progress.
Automatic MCAL GRB alert Notice

A. Ridnaia, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin,
and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and A. Ursi, F. Verrecchia, M. Tavani, N. Parmiggiani, C. Pittori,
A. Bulgarelli, on behalf of the AGILE team, report:

The short-duration GRB 200920B
(AGILE/MCAL detection: Ursi et al., GCN Circ. 28464
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 )
has been detected by Fermi (GBM trigger 622324624), Konus-Wind,
INTEGRAL (SPI-ACS), and AGILE (MCAL), so far,
at about 71815 s UT (19:56:55).

We have triangulated it to a Konus-GBM annulus centered at
RA(2000)=157.135 deg (10h 28m 32s)  Dec(2000)=+10.976 deg (+10d 58' 33"),
whose radius is 4.834 +/- 1.787 deg (3 sigma),
to a Konus-INTEGRAL annulus centered at
RA(2000)=154.111 deg (10h 16m 27s)  Dec(2000)=+8.715 deg (+8d 42' 54"),
whose radius is 7.120 +/- 1.815 deg (3 sigma), and
to a GBM-INTEGRAL annulus centered at
RA(2000)=77.242 deg (05h 08m 58s)  Dec(2000)=-35.743 deg (-35d 44' 36"),
whose radius is 90.000 +/- 4.602 deg (3 sigma).

The preliminary, 3 sigma error box is:
 ---------------------------------------------
  RA(2000), deg       Dec(2000), deg
 ---------------------------------------------
 Center:
  160.5209           +13.4321
 Corners:
  161.4146           +14.0653
  155.8758           +17.4839
  150.6190           +12.7611
  155.8316           +13.7440
  159.6319           +12.7958
  159.4728           +8.9807
  157.1525           +4.3546
  163.1097           +7.9563
 ---------------------------------------------
The error box area is 51.5 sq. deg, and its maximum
dimension is 13.2 deg (the minimum one is 2.1 deg).
The Sun distance was 123 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB200920_T71814/IPN/

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

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

The short-duration GRB 200920B
(AGILE/MCAL detection: Ursi et al., GCN Circ. 28464
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 ;
IPN triangulation: Ridnaia et al., GCN Circ. 28467
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 )
triggered Konus-Wind at T0=71814.617 s UT (19:56:54.617).

The burst light curve shows a multi-peaked structure
which started at ~T0-0.368 s and had a total duration of ~0.37 s.

The K-W light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB200920_T71814/

As observed by Konus-Wind, the burst had a fluence of
3.12(-0.61,+0.94)x10^-6 erg/cm2 and a 16-ms peak flux,
measured from ~T0-0.260 s, of 1.74(-0.52,+0.65)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Since the bulk of the burst emission was detected before
the trigger, the spectral analysis was performed using
the KW 3-channel light curve data.

Modelling the K-W 3-channel spectrum of the burst
(measured from T0-0.368 s to T0)
by the cutoff power law yields the following model parameters:
the photon index alpha = 0.15(-0.51,+0.95),
and the peak energy Ep = 935(-241,+401) keV.

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.