TITLE:   GCN CIRCULAR
NUMBER:  32904
SUBJECT: GRB 221028A: Detection by VZLUSAT-2
DATE:    22/11/01 18:05:11 GMT
FROM:    Jakub Ripa at Masaryk University  <245487@mail.muni.cz>

J. Ripa (Masaryk U.), 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, M. Dafcikova, 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.

A long-duration GRB 221028A (Swift/BAT detection: Lien et al., GCN Circ. 
32874; AGILE detection: Ursi et al., GCN Circ. 32885; KONUS-Wind 
detection: trig. time 2022-10-28 13:16:29.550 UT; INTEGRAL/SPI-ACS 
detection peak at 2022-10-28 13:16:28.3 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 7.1 (6.1) sigma detection significance was confirmed at detector 
unit no. 0 (no. 1) at 2022-10-28 13:16:26 UTC. The T90 duration was 
measured to be 23 s (26 s) for detector unit no. 0 (no. 1).

The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB221028A_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.