GCN Circular 33605

M. Dafcikova, 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, 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 long duration GRB 230409D (Fermi/GBM detection: trigger no. 702745263;
Konus/Wind detection at 2023-04-09 15:00:59.219; INTEGRAL/SPI-ACS detection
at 2023-04-09 15:00:59) was detected by the GRB detector on board of the
VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/).

The data acquisition was performed by the GRB detector units no. 0 and no.
1. The detection was confirmed at the peak time 2023-04-09 15:01:08 UTC.
The T90 duration measured by VZLUSAT-2 is 19 s (15 s) and the significance
during T90 reaches 26 sigma (12 sigma) for detector unit no. 0 (no. 1).

The light curve obtained by VZLUSAT-2 is available here:

https://vzlusat2.konkoly.hu/static/share/GRB230409D_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 ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13
from Cape Canaveral.