TITLE:   GCN CIRCULAR
NUMBER:  33418
SUBJECT: GRB 230307A: Detection by GRBAlpha
DATE:    23/03/08 11:23:01 GMT
FROM:    Marianna Dafcikova at Masaryk University  <500025@mail.muni.cz>

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), N. Husarikova, F. Munz , M. Topinka, M. Kolar, J.-P.
Breuer, 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 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) was observed by the GRBAlpha 1U CubeSat (Pal et
al. Proc. SPIE 2020).


The detection was confirmed at the peak time 2023-03-07 15:44:12 UTC. The
T90 duration measured by GRBAlpha is 25 s and the overall significance
during T90 reaches 305 sigma. GRBAlpha entered the outer Van Allen
radiation belt during the tail part of the burst.

The peak count rate detected by GRBAlpha reaches almost 10 000 counts/s,
which is nearly half of the peak count rate of 22 000 counts/s measured for
GRB221009A.


The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB230307A_GCN.pdf


All GRBAlpha detections are listed at:
https://monoceros.physics.muni.cz/hea/GRBAlpha/

GRBAlpha, launched on 2021 March 22, is a demonstration mission for a
future CubeSat 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. 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.