GRB 240914B

T. Preis, B. Biltzinger, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
747990592 at 07:09:47 on 14 Sept. 2024 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position is:
RA(2000.0) = 291.4 deg
Decl.(2000.0) = 30.3 deg
The 1 sigma statistical error radius is 1.9 deg.
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB240914298/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB240914298/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB240914298/json

                        

S. Srijan (IITB), G. Waratkar (IITB), J. Joshi (IUCAA), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 240914B which was also detected by Fermi/GBM (Trigger 747990592, Preis et al., GCN Circ. 37496
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 ). Inspection of INTEGRAL/SPI-ACS data also showed the detection of the burst.

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2024-09-14 07:09:51 UTC. The measured peak count rate associated with the burst is 548 (+47, -43) counts/s above the background in the combined data of all quadrants, with a total of 3654 (+291, -307) counts. The local mean background count rate was 319 (+4, -5) counts/s. Using cumulative rates, we measure a T90 of 11.0 (+2.7,  -1.4) s. In the preliminary analysis, we find 388 Compton events associated with this event.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2024-09-14 07:09:51 UTC. The measured peak count rate is 795 (+76, -82) counts/s above the background in the combined Veto data of all quadrants, with a total of 4083 (+602, -597) counts. The local mean background count rate was 1342 (+8, -9) counts/s. We measure a T90 of 7.9 (+4.4, -1.6) s from the cumulative Veto light curve.

CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.

CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb

The Fermi GBM team reports the detection of a likely LONG GRB

"At 07:09:47.31 UT on 14 September 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240914B (trigger 747990592/240914298).

The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 293.61, Dec = 29.25 (J2000 degrees, equivalent to J2000 19h 34m, +29d 15'),
with a statistical uncertainty of 2.36 degrees.

The angle from the Fermi LAT boresight is 52 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240914298/quicklook/glg_skymap_all_bn240914298.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240914298/quicklook/glg_healpix_all_bn240914298.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240914298/quicklook/glg_lc_medres34_bn240914298.gif"

M. Dafcikova, J. Ripa, M. Kolar (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. Duriskova, L. Szakszonova, 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 long-duration GRB 240914B (AstroSat/CZTI detection: GCN 37506
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 ; Fermi/GBM detection: GCN 37524
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 ; INTEGRAL/SPI-ACS detection: trigger no. 10905) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract).

The detection was confirmed at the peak time 2024-09-14 07:09:51.1 UTC. The T90 duration measured by GRBAlpha is 21.0 s and the overall significance during T90 reaches 18 sigma.

The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB240914B_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.