TITLE:   GCN CIRCULAR
NUMBER:  33424
SUBJECT: GRB 230307A: VZLUSAT-2 detection
DATE:    23/03/08 18:13:06 GMT
FROM:    Jakub Ripa at Masaryk University  <245487@mail.muni.cz>

J. Ripa (Masaryk U.), M. Dafcikova, A. Pal (Konkoly Observatory), N. 
Werner  (Masaryk U.), M. Ohno (Hiroshima U.),  L. Meszaros, B. Csak 
(Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. 
Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (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 extremely bright long-duration GRB 230307A (Fermi/GBM detection: GCN 
33405, 33407, 33411, 33414; GECAM-B detection: GCN 33406; Solar Orbiter 
STIX detection: GCN 33410; AGILE/MCAL detection: GCN 33412; IPN 
triangulation: GCN 33413; AstroSat detection: GCN 33415; BALROG 
localization: GCN 33416; GRBAlpha detection: GCN 33418) was detected by 
the GRB detectors 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 detection was confirmed at the peak time 2023-03-07 15:44:11 UTC. 
The T90 duration measured by VZLUSAT-2 is 28 s (34 s) and the 
significance during T90 reaches 219 sigma (213 sigma) for detector unit 
no. 0 (no. 1).

The light curves obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB230307A_GCN_VZLUSAT2.pdf

All VZLUSAT-2 detections are listed at:
https://monoceros.physics.muni.cz/hea/VZLUSAT-2/

The GRB detectors on VZLUSAT-2 are a demonstration payload for a future 
CubeSat 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 ~40 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 
January 13 from Cape Canaveral.