GRB 240905B
GCN Circular 37389
Subject
GRB 240905B: Fermi GBM Final Real-time Localization
Date
2024-09-05T04:37:48Z (9 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely SHORT GRB
At 04:27:16 UT on 5 Sep 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240905B (trigger 747203241.139826 / 240905186).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 266.1, Dec = 16.9 (J2000 degrees, equivalent to J2000 17h 44m, 16d 53'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 25.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240905186/quicklook/glg_skymap_all_bn240905186.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/bn240905186/quicklook/glg_healpix_all_bn240905186.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240905186/quicklook/glg_lc_medres34_bn240905186.gif
GCN Circular 37391
Subject
GRB 240905B: AstroSat CZTI detection and localization
Date
2024-09-05T10:11:21Z (9 months ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
J. Joshi (IUCAA), U. Pathak (IITB), G. Waratkar (IITB), G. Parwani (IITB), J. V. Aditya (IITB), D. Saraogi (IITB), 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 short-duration GRB 240905B which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 37386). 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 2024-09-05 04:27:16.55 UTC. The measured peak count rate associated with the burst is 3849 (+853, -293) counts/s above the background in the combined data of all quadrants, with a total of 1531 (+95, -118) counts. The local mean background count rate was 326 (+22, -23) counts/s. Using cumulative rates, we measure a T90 of 0.67 (+0.11, -0.06) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2024-09-05 04:27:16.29 UTC. The measured peak count rate associated with the burst is 3645 (+109, -119) counts/s above the background in the combined data of all quadrants, with a total of 4282 (+150, -157) counts. The local mean background count rate was 1276 (+9, -10) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it.
We localised the burst using the AstroSat/CZTI localization framework (Saraogi et al., 2024, MNRAS, 530, 2; doi:10.1093/mnras/stae435) and obtained a multi-modal distribution. The global minimum spans a broad swath around Dec=+60, with an RA range of 220-320 degrees. A slightly shallower but better defined minimum is seen at RA, Dec = 260, +15 which is consistent with Fermi/GBM localization (Fermi GBM team, GCN Circ. 37386). The probability contours can be seen at this link:
https://bighome.iitb.ac.in/index.php/s/JgJ7s3426kxyRWC
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
GCN Circular 37393
Subject
Fermi GRB 240905B: Global MASTER-Net observations report
Date
2024-09-05T11:30:40Z (9 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
legacy email
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko,
G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij
(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova
(Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich
(Blagoveschensk Educational State University)
MASTER-Amur robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Blagoveshchensk State Pedagogical University) started inspect of the Fermi GRB 240905B ( Fermi GBM team, GCN 37389) errorbox 23620 sec after notice time and 23653 sec after trigger time at 2024-09-05 11:01:29 UT, with upper limit up to 16.2 mag. Observations started at twilight. The observations began at zenith distance = 35 deg. The sun altitude is -9.3 deg.
The galactic latitude b = 22 deg., longitude l = 41 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2589953
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
23684 | 2024-09-05 11:01:29 | MASTER-Amur | (17h 37m 46.69s , +16d 24m 43.3s) | C | 60 | 16.2 |
23763 | 2024-09-05 11:02:49 | MASTER-Amur | (17h 46m 01.25s , +16d 24m 00.3s) | C | 60 | 16.1 |
23865 | 2024-09-05 11:04:31 | MASTER-Amur | (17h 48m 50.82s , +18d 19m 37.2s) | C | 60 | 15.8 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 37417
Subject
GRB 240905B: Swift ToO observations
Date
2024-09-07T02:31:03Z (9 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/LAT GRB 240905B.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021711
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/LAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 37418
Subject
GRB 240905B: Fermi-LAT detection
Date
2024-09-07T03:07:29Z (9 months ago)
Edited On
2024-09-07T03:35:06Z (9 months ago)
From
Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Rahul Gupta at NASA GSFC <rahul.gupta@nasa.gov>
Via
email
R. Gupta (NASA GSFC), N. Di Lalla (Stanford University), and D. Kocevski (NASA/MSFC) report on behalf of the Fermi-LAT Collaboration:
On Sep 05, 2024, Fermi-LAT detected high-energy emission from GRB 240905B, which was also detected by Fermi-GBM (trigger 747203241.139826 / 240905186), and AstroSat CZTI (GCN 37391).
The best LAT on-ground location is found to be:
RA, Dec = 268.0, 14.2 (J2000)
with an error radius of 0.2 deg (90 % containment, statistical error only).
This was 28 deg from the LAT boresight at the time of the GBM trigger: T0 = 04:27:16 UT.
The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 0-10 s after the GBM trigger is (2.2 +/- 0.6) E-4 ph/cm2/s. The estimated photon index above 100 MeV is -2.0 +/- 0.3.
The highest-energy photon is a 3 GeV event which is observed ~ 1.1 seconds after the GBM trigger.
A Swift ToO has been approved for this burst.
The Fermi-LAT point of contact for this burst is Niccolo' Di Lalla (niccolo.dilalla@stanford.edu).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular 37421
Subject
GRB 240905B: Swift-XRT observations
Date
2024-09-07T15:02:06Z (9 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Dichiara (PSU), J.A.
Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester), A. Melandri (INAF-OAR) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 240905B, collecting 4.7 ks of Photon
Counting (PC) mode data between T0+165.8 ks and T0+184.5 ks.
Six uncatalogued X-ray sources have been detected, however none of them
is above the RASS limit or shows definitive signs of fading. Therefore,
at the present time we cannot identify which, if any, is the afterglow.
Details of these sources are given below:
Source 1:
RA (J2000.0): 267.9656 = 17:51:51.73
Dec (J2000.0): +14.3317 = +14:19:54.0
Error: 5.3 arcsec (radius, 90% conf.)
Count-rate: (7.5 [+1.7, -1.6])e-3 ct s^-1
Distance: 489 arcsec from Fermi/LAT position.
Flux: (1.21 [+0.28, -0.26])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Source 2:
RA (J2000.0): 267.8714 = 17:51:29.15
Dec (J2000.0): +14.1724 = +14:10:20.6
Error: 6.1 arcsec (radius, 90% conf.)
Count-rate: (2.45 [+1.16, -0.91])e-3 ct s^-1
Distance: 459 arcsec from Fermi/LAT position.
Source 3:
RA (J2000.0): 268.0531 = 17:52:12.75
Dec (J2000.0): +14.1172 = +14:07:01.9
Error: 6.3 arcsec (radius, 90% conf.)
Count-rate: (1.14 [+0.99, -0.76])e-3 ct s^-1
Distance: 351 arcsec from Fermi/LAT position.
Source 4:
RA (J2000.0): 268.1019 = 17:52:24.47
Dec (J2000.0): +14.0362 = +14:02:10.2
Error: 6.5 arcsec (radius, 90% conf.)
Count-rate: (4.5 [+1.5, -1.3])e-3 ct s^-1
Distance: 688 arcsec from Fermi/LAT position.
Flux: (1.10 [+0.38, -0.31])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Source 5:
RA (J2000.0): 268.0524 = 17:52:12.56
Dec (J2000.0): +14.2532 = +14:15:11.5
Error: 5.9 arcsec (radius, 90% conf.)
Count-rate: (1.11 [+0.86, -0.69])e-3 ct s^-1
Distance: 264 arcsec from Fermi/LAT position.
Source 6:
RA (J2000.0): 267.9614 = 17:51:50.74
Dec (J2000.0): +14.2308 = +14:13:51.0
Error: 7.4 arcsec (radius, 90% conf.)
Count-rate: (1.41 [+0.93, -0.75])e-3 ct s^-1
Distance: 174 arcsec from Fermi/LAT position.
Flux: (3.8 [+2.5, -2.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021711.
This circular is an official product of the Swift-XRT team.
GCN Circular 37433
Subject
GRB 240905B: GOTO optical upper limits
Date
2024-09-09T10:53:22Z (9 months ago)
From
Amit Kumar at University of Warwick, UK <amitkundu515@gmail.com>
Via
Web form
A. Kumar, D. O'Neill, B. P. Gompertz, J. Lyman, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, K. Ulaczyk, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration:
We report on observations with the Gravitational-wave Optical Transient Observer (GOTO, Steeghs et al. 2022) in response to GRB 240905B (Fermi GBM team, GCN 37389; Joshi et al., GCN 37391; Gupta et al., GCN 37418). Targeted observations of the GBM localisation were performed by GOTO North and South from 2024-09-05 09:29:19 UT to 2024-09-06 00:48:53 UT (respectively from +5.03 to +20.33 hours after trigger) distributed over four epochs. Each observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using recent survey observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues. Human vetting was carried out in real time on any candidates that passed the above checks.
No candidate optical counterparts are identified within a circular region of radius 0.2 degrees centered on the Fermi/LAT localisation (Gupta et al., GCN 37418). The typical depth of the most constraining image is L > 20.7 mags (5-sigma), taken at 09:36:50 UT on 2024-09-05 (~5.1 hours after the GBM trigger). Forced photometry at the positions of 6 Swift/XRT detected uncatalogued X-ray sources (Brivio et al., GCN 37421) in this image similarly provides 5-sigma limiting L-band magnitudes of ~20.7 on each.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and were not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 37436
Subject
GRB 240905B: Fermi GBM Observation
Date
2024-09-09T16:29:13Z (9 months ago)
From
Sarah Dalessi at UAH <sd0104@uah.edu>
Via
Web form
S. Dalessi (UAH), A. Myers (NPP/GSFC) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 04:27:16.14 UT on 05 September 2024, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 240905B (trigger 747203241/240905186).
which was also detected by AstroSat (J. Joshi et al. 2024, GCN 37391) and Fermi-LAT (R. Gupta et al. 2024, GCN 37418).
The Fermi GBM on-ground location is consistent with the AstroSat and Fermi-LAT positions.
The angle from the Fermi LAT boresight is 25 degrees.
The GBM light curve single emission episode with a duration (T90)
of about 1.3 s (50-300 keV). The time-averaged spectrum
from T0+0 to T0+1.280 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.36 +/- 0.04 and the cutoff energy,
parameterized as Epeak, is 1240 +/- 70 keV.
The event fluence (10-1000 keV) in this time interval is
(5.11 +/- 0.08)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.32 s in the 10-1000 keV band is 30 +/- 1 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 1223 +/- 70 keV, alpha = -0.36 +/- 0.04 and beta = -4.16 +/- 1.24.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 37455
Subject
IPN triangulation of GRB 240905B (short)
Date
2024-09-11T15:24:31Z (9 months ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the MGNS/BepiColombo team,
J. Benkhoff on behalf of the BepiColombo team,
D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,
A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,
E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and
G. Waratkar, V. Jethwani, J.Joshi, V. Bhalerao, D. Bhattacharya,
and S. Vadawale, on behalf of the Astrosat-CZTI team, report:
The short-duration GRB 240905B
(Fermi-GBM detection: The Fermi GBM team, GCN 37389;
Dalessi et al., GCN 37436;
AstroSat-CZTI detection: Joshi et al., GCN 37391;
Fermi-LAT detection: Gupta et al., GCN 37418)
was detected by Fermi (GBM and LAT), Konus-Wind, INTEGRAL (SPI-ACS),
Astrosat (CZTI), and BepiColombo (MGNS) at about 16036 s UT (04:27:16).
We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
267.922 (17h 51m 41s) +14.240 (+14d 14' 24")
Corners:
267.264 (17h 49m 03s) +12.544 (+12d 32' 40")
267.181 (17h 48m 43s) +12.565 (+12d 33' 54")
268.618 (17h 54m 28s) +15.927 (+15d 55' 37")
268.703 (17h 54m 49s) +15.906 (+15d 54' 21")
---------------------------------------------
The error box area is 1087 sq. arcmin, and its maximum
dimension is 3.65 deg (the minimum one is 5 arcmin).
The Sun distance was 100 deg.
This localization may be improved.
The IPN localization is consistent with, but reduces the area of,
the Fermi-LAT localization.
Swift-XRT reported six afterglow candidates for this burst (Source 1-6, Brivio et. al., GCN 37421). Three candidates (Sources 1, 2, and 6) are inside the IPN box.
A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB240905_T16038/IPN/
The HEALPix triangulation map is the multi-order HEALPix in units of
probability density.
The Konus-Wind time history and spectrum will be given
in a forthcoming GCN Circular.
GCN Circular 37601
Subject
GRB 240905B: VZLUSAT-2 detection
Date
2024-09-24T17:57:04Z (8 months ago)
From
Marianna Dafčíková at Masaryk University <500025@mail.muni.cz>
Via
Web form
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 short-duration GRB 240905B (Fermi/GBM detection: GCN 37389; AstroSat/CZTI detection: GCN 37391; Konus/Wind detection at 2024-09-05 04:27:18.558 UTC; INTEGRAL/SPI-ACS peak detection at 2024-09-05 ~04:27:16 UTC) 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 unit no. 1. The detection was confirmed at the peak time 2024-09-05 04:27:15 UTC. The T90 duration is 1 s and the significance during T90 reaches 11 sigma.
The light curve obtained by VZLUSAT-2 is available here:
https://vzlusat2.konkoly.hu/static/share/GRB240905B_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.
GCN Circular 37613
Subject
Konus-Wind detection of GRB 240905B
Date
2024-09-26T15:50:34Z (8 months ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
Via
Web form
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova,
A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:
The short-duration GRB 240905B
(Fermi-GBM detection: The Fermi GBM team, GCN 37389; Dalessi et al., GCN 37436;
AstroSat-CZTI detection: Joshi et al, GCN 37391;
Fermi-LAT detection: Gupta et al., GCN 37418;
IPN triangulation: Kozyrev et al., GCN 37455;
VZLUSAT-2 detection: Dafcikova et al., GCN 37601)
triggered Konus-Wind at T0=16038.558 s UT (04:27:18.558).
The burst light curve shows a multipeaked structure
which starts at ~T0-0.1 s and has a total duration of ~1 s.
The emission is seen up ~5 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240905_T16038/
As observed by Konus-Wind, the burst
had a fluence of 1.68(-0.28,+0.35)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.432 s,
of 4.13(-1.05,+1.17)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.54(-0.18,+0.21)
and Ep = 1229(-251,+357) keV (chi2 = 92/87 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.2
(chi2 = 92/86 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.