GRB 220320A

R. Gopalakrishnan (IUCAA), V. Prasad (IUCAA), A. Suresh (IITB), G.
Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya
(IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf
of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data with the ML pipeline (Abraham et al.,
2021, MNRAS, 504, 3084) and the CIFT framework (Sharma et al., 2021,
JApA, 42, 73) showed detection of a bright long GRB 220320A which was
also detected by IPN (contributed by Konus-Wind at GCN Notices), and
Fermi - GBM (Trigger - 669443999).

The source was clearly detected in the 20-200 keV energy range. The
light curve peaks at 2022-03-20 04:39:59.25 UT. The measured peak count
rate associated with the burst is 2398 (+336, -71) counts/s above the
background in the combined data of four quadrants, with a total of 5427
(+307, -331) counts. The local mean background count rate was 507 (+5,
-9) counts/s. Using cumulative rates, we measure a T90 of 11 (+1, -1) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed a peak at
2022-03-20 04:39:59.13 UT. The measured peak count rate is 3438 (+112,
-122) counts/s  above the background in the combined Veto data of four
quadrants, with a total of 10543 (+502, -570) counts. The local mean
background count rate was 1529 (+5, -5) counts/s. We measure a T90 of 16
(+3, -3) s from the cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC,
and PRL. The Indian Space Research Organisation funded, managed, and
facilitated the project. 

Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb

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

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,

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

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

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:

The bright, long-duration GRB 220320A
(AstroSat-CZTI detection: Gopalakrishnan et al., GCN Circ. 31779
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 )
was detected by Fermi (GBM trigger 669443999), Konus-Wind,
INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), BepiColombo (MGNS),
CALET (CGBM), and AstroSat (CZTI) at about 16794 s UT (04:39:54).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
    94.150 (06h 16m 36s) -55.909 (-55d 54' 31")
  Corners:
    94.226 (06h 16m 54s) -55.949 (-55d 56' 58")
    94.048 (06h 16m 12s) -55.915 (-55d 54' 54")
    94.074 (06h 16m 18s) -55.868 (-55d 52' 04")
    94.252 (06h 17m 00s) -55.902 (-55d 54' 08")
  ---------------------------------------------
The error box area is 19 sq. arcmin, and its maximum
dimension is 7 arcmin (the minimum one is 3 arcmin).
The Sun distance was 92 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi GBM final position.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB220320_T16796/IPN

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

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

The long-duration, bright GRB 220320A
(AstroSat CZTI detection: Gopalakrishnan et al., GCN 31779
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 ;
IPN triangulation: Kozyrev et al., GCN 31783
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 )
triggered Konus-Wind at T0=16796.141 s UT (04:39:56.141).

The burst light curve shows a multi-peaked structure
which starts at ~T0-18.8 s and has a total duration of~52.8 s
The emission is seen up to ~20 MeV.

As observed by Konus-Wind, the burst
had a fluence of 6.05(-0.50,+0.52)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+4.048 s,
of 2.50(-0.34,+0.34)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+20.480 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.84(-0.09,+0.10),
the high energy photon index beta = -2.27(-0.15,+0.11),
the peak energy Ep = 224(-21,+24) keV,
chi2 = 100/97 dof.

The spectrum near the peak count rate
(measured from T0 to T0+4.352 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.43(-0.11,+0.12),
the high energy photon index beta = -2.31(-0.17,+0.13),
the peak energy Ep = 311(-29,+33) keV,
chi2 = 67/86 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220320_T16796/

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

J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), M. Ohno (Eotvos 
U./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.

The bright, long-duration GRB 220320A (AstroSat-CZTI detection: 
Gopalakrishnan et al., GCN Circ. 31779
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 ; localized by IPN: Kozyrev et al. 
GCN Circ. 31783
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  and detected also by Fermi/GBM trigger 669443999, 
CALET/CGBM trigger 1331786356, Konus-Wind, INTEGRAL/SPI-ACS at about 
04:39:54 UT) was also detected by one of the two GRB detectors on board 
of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

This is the first time that a GRB was observed by the VZLUSAT-2 3U CubeSat.

The data acquisition was performed by GRB detector unit no. 1 (the unit 
no. 0 was turned off). The detector was performing a several hours long 
background monitoring survey with 15 s temporal resolution, which is not 
optimal for GRB search. Much finer resolution is planned for the nominal 
operation. The 46 sigma detection significance was confirmed at around 
04:39:55 UTC.

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB220320A_GCN_VZLUSAT_2.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.