TITLE:   GCN CIRCULAR
NUMBER:  34664
SUBJECT: GRB 230911B: GRBAlpha and VZLUSAT-2 joint detection
DATE:    23/09/11 20:36:40 GMT
FROM:    Marianna Dafčíková 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.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Poon, 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 (U. Tokyo), K. Torigoe, Y. Uchida (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), T. Bozoki, G. Dalya, G. Friss, K. Kapas, J. Takatsy (Eotvos U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha and VZLUSAT-2/GRB payload collaborations

We report a joint detection of a long-duration GRB 230911B by the GRBAlpha 1U CubeSat (Pal et al. 2023; arXiv:2302.10048) and the GRB detector on board of VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The event was also observed by Fermi/GBM (GCN 34653) and INTEGRAL/SPI-ACS at ~2023-09-11 04:25:51 UT.

The GRBAlpha detection was confirmed at the peak time 2023-09-11 04:25:51 UTC. The T90 duration is 15 s and the significance during T90 reaches 13 sigma.

The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB230911B_GCN.pdf

The VZLUSAT-2 detection was confirmed at the peak time 2023-09-11 04:25:50 UTC. The data acquisition was performed by the GRB detector unit no. 1. The T90 duration is 15 s and the significance during T90 reaches 9 sigma.

The light curves obtained by VZLUSAT-2 are available here:
https://vzlusat2.konkoly.hu/static/share/GRB230911B_GCN_VZLUSAT2.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. 

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.