GCN Circular 32781

M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. 
Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, 
B. Csak (Konkoly Observatory), F. Munz, N. Husarikova, J.-P. Breuer, M. 
Topinka, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal,�� A. Povalac (Brno 
U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. 
Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky 
(Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos 
U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida 
(ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto 
(Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. 
Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), 
K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory),�� T. Mizuno 
(Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. 
Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama 
(Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) 
-- the GRBAlpha collaboration.

The long-duration GRB 220926B (INTEGRAL IBIS/ISGRI detection: Gotz et 
al., GCN 32586
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 ) was detected by the GRBAlpha 1U CubeSat (Pal et al. 
Proc. SPIE 2020).

The subthreshold 4.7 sigma detection was confirmed at the peak time 
2022-09-26 10:38:21.2 UTC. The light curve obtained by GRBAlpha is 
temporally consistent with the light curve obtained by INTEGRAL 
IBIS/ISGRI. The GOES X-ray flux does not show any excess, so we exclude 
this detection being a solar flare. Therefore, this event is consistent 
with being a GRB with a duration, as measured by GRBAlpha, of ~8 s.

The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB220926B_GCN.pdf

GRBAlpha, launched on 2021 March 22, is a demonstration mission for a 
future CubeSat constellation (Werner et al. Proc. SPIE 2018). Its 
detector consists of a 75 x 75 x 5 mm^3 CsI(Tl) scintillator read out by 
a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To 
increase the duty cycle and the downlink rate, we are continuously 
upgrading the on-board data acquisition software stack. The ground 
segment is also supported by the radio amateur community and it takes 
advantage of the SatNOGS network for increased data downlink volume.