TITLE:   GCN CIRCULAR
NUMBER:  30697
SUBJECT: GRB 210822A: Detection by GRBAlpha
DATE:    21/08/23 15:42:18 GMT
FROM:    Masanori Ohno at Hiroshima U  <ohno@astro.hiroshima-u.ac.jp>

M. Ohno (Eotvos U./Konkoly Observatory/Hiroshima U.), J. Ripa (Masaryk U.),
 H. Takahashi (Hiroshima U.), A. Pal, L. Meszaros, B. Csak (Konkoly
Observatory), N. Werner, M. Topinka, F. Munz, 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.), Yuusuke Uchida, Helen Poon, H. Matake, N.
Uchida (Hiroshima U.), 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.) -- the GRBAlpha
collaboration.

The long duration GRB 210822A (Swift-BAT detection; Page et al. GCN Circ.
 30677, GECAM detection; Wang et al. GCN Circ. 30678, Fermi-LAT detection;
Ohno et al. GCN Circ. 30687) was detected by the GRBAlpha 1U CubeSat (Pal
et al. Proc. SPIE 2020).

The light curve shows a strong spike structure with a high significance of
a SNR ~ 45. The observed total duration was about 12 sec. GRBAlpha was
leaving the outer Van Allen radiation belt and thus GRB 210822A is
superimposed on a high background due to trapped electrons.

The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB210822A_GCN.pdf

GRBAlpha is a demonstration mission for a future CubeSats constellation
(Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75
x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy
range from ~50 keV to ~1000 keV. GRBAlpha was launched on 2021 March 22
from Baikonur. After its commissioning phase, the scientific observations
are now under way. To increase the duty cycle and the downlink rate, the
upgrade of the on-board data acquisition software stack is in progress. The
ground segment is also supported by the radio amateur community and it
takes advantage of the SatNOGS network for increased data downlink volume.