Gamma-ray Burst 250313A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #39703
The Fermi GBM team reports the detection of a likely LONG GRB
At 14:34:33 UT on 13 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250313A (trigger 763569278.689058 / 250313607).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 276.4, Dec = 51.8 (J2000 degrees, equivalent to J2000 18h 25m, 51d 47'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 4.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250313607/quicklook/glg_skymap_all_bn250313607.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250313607/quicklook/glg_healpix_all_bn250313607.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250313607/quicklook/glg_lc_medres34_bn250313607.gif
GCN Circular #39704
T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger at 14:34:33 on 13 March 2025 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) = 274.6 deg
Decl.(2000.0) = 45.3 deg
```
The 1 sigma statistical error radius is 0.1 deg. We estimate an additional systematic error of 2 deg.
Further details are available at: https://grb.mpe.mpg.de/grb/GRB250313607/
The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250313607/healpix
The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250313607/json

GCN Circular #39706
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 250313A ( Fermi GBM team, GCN 39703) errorbox 6499 sec after notice time and 6531 sec after trigger time at 2025-03-13 16:23:25 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 64 deg. The sun altitude is -40.5 deg.
MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250313A errorbox 13836 sec after notice time and 13867 sec after trigger time at 2025-03-13 18:25:41 UT, with upper limit up to 16.3 mag. The observations began at zenith distance = 79 deg. The sun altitude is -34.2 deg.
The galactic latitude b = 25 deg., longitude l = 80 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2811112
We obtain a following upper limits.

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    6534 | 2025-03-13 16:23:25 |        MASTER-Tunka | (18h 26m 19.46s , +51d 36m 23.5s) |   C |     5 | 15.9 |        
    6539 | 2025-03-13 16:23:25 |        MASTER-Tunka | (18h 26m 19.46s , +51d 36m 23.4s) |   C |    15 | 16.6 |  Coadd 
    6553 | 2025-03-13 16:23:43 |        MASTER-Tunka | (18h 26m 25.64s , +51d 35m 22.8s) |   C |     5 | 16.1 |        
    6570 | 2025-03-13 16:24:01 |        MASTER-Tunka | (18h 26m 19.56s , +51d 34m 23.6s) |   C |     5 | 16.1 |        
    6588 | 2025-03-13 16:24:18 |        MASTER-Tunka | (18h 26m 25.38s , +51d 34m 41.3s) |   C |     5 | 16.0 |        
    6593 | 2025-03-13 16:24:18 |        MASTER-Tunka | (18h 26m 25.37s , +51d 34m 41.2s) |   C |    15 | 16.7 |  Coadd 
    6607 | 2025-03-13 16:24:37 |        MASTER-Tunka | (18h 26m 22.64s , +51d 36m 18.7s) |   C |     5 | 16.1 |        
    6624 | 2025-03-13 16:24:54 |        MASTER-Tunka | (18h 26m 22.61s , +51d 34m 53.1s) |   C |     5 | 16.0 |        
    6645 | 2025-03-13 16:25:14 |        MASTER-Tunka | (18h 26m 24.91s , +51d 36m 10.2s) |   C |    10 | 16.4 |        
    6655 | 2025-03-13 16:25:14 |        MASTER-Tunka | (18h 26m 24.93s , +51d 36m 10.4s) |   C |    30 | 16.9 |  Coadd 
    6669 | 2025-03-13 16:25:37 |        MASTER-Tunka | (18h 26m 20.02s , +51d 35m 25.5s) |   C |    10 | 16.3 |        
    6693 | 2025-03-13 16:26:02 |        MASTER-Tunka | (18h 26m 19.41s , +51d 36m 26.4s) |   C |    10 | 16.4 |        
    6718 | 2025-03-13 16:26:26 |        MASTER-Tunka | (18h 26m 25.99s , +51d 35m 26.4s) |   C |    10 | 16.4 |        
    6728 | 2025-03-13 16:26:26 |        MASTER-Tunka | (18h 26m 26.01s , +51d 35m 25.7s) |   C |    30 | 17.0 |  Coadd 
    6742 | 2025-03-13 16:26:50 |        MASTER-Tunka | (18h 26m 21.05s , +51d 34m 26.9s) |   C |    10 | 16.5 |        
    6763 | 2025-03-13 16:27:12 |        MASTER-Tunka | (18h 26m 26.84s , +51d 34m 44.6s) |   C |    10 | 16.5 |        
    6786 | 2025-03-13 16:27:34 |        MASTER-Tunka | (18h 26m 23.48s , +51d 36m 23.8s) |   C |    10 | 16.5 |        
    6796 | 2025-03-13 16:27:34 |        MASTER-Tunka | (18h 26m 23.48s , +51d 36m 23.5s) |   C |    30 | 17.1 |  Coadd 
    6809 | 2025-03-13 16:27:57 |        MASTER-Tunka | (18h 26m 23.42s , +51d 34m 40.4s) |   C |    10 | 16.5 |        
    6834 | 2025-03-13 16:28:22 |        MASTER-Tunka | (18h 26m 26.91s , +51d 36m 01.6s) |   C |    10 | 16.5 |        
    8874 | 2025-03-13 17:02:22 |        MASTER-Tunka | (18h 26m 31.04s , +51d 36m 22.5s) |   C |    10 | 16.9 |        
    8884 | 2025-03-13 17:02:22 |        MASTER-Tunka | (18h 26m 31.07s , +51d 36m 23.1s) |   C |    30 | 17.5 |  Coadd 
    8919 | 2025-03-13 17:02:22 |        MASTER-Tunka | (18h 26m 31.07s , +51d 36m 22.8s) |   C |   100 | 18.2 |  Coadd 
    9009 | 2025-03-13 17:02:22 |        MASTER-Tunka | (18h 26m 31.05s , +51d 36m 22.9s) |   C |   280 | 18.9 |  Coadd 
    9139 | 2025-03-13 17:02:22 |        MASTER-Tunka | (18h 26m 31.07s , +51d 36m 23.0s) |   C |   540 | 19.2 |  Coadd 
    8899 | 2025-03-13 17:02:47 |        MASTER-Tunka | (18h 26m 29.42s , +51d 37m 23.3s) |   C |    10 | 16.9 |        
    8922 | 2025-03-13 17:03:10 |        MASTER-Tunka | (18h 26m 35.91s , +51d 36m 23.6s) |   C |    10 | 16.9 |        
    8945 | 2025-03-13 17:03:33 |        MASTER-Tunka | (18h 26m 30.59s , +51d 35m 24.2s) |   C |    10 | 16.8 |        
    8955 | 2025-03-13 17:03:33 |        MASTER-Tunka | (18h 26m 30.61s , +51d 35m 24.4s) |   C |    30 | 17.5 |  Coadd 
    8978 | 2025-03-13 17:04:07 |        MASTER-Tunka | (18h 26m 36.90s , +51d 35m 42.9s) |   C |    10 | 16.8 |        
    9010 | 2025-03-13 17:04:38 |        MASTER-Tunka | (18h 26m 33.86s , +51d 37m 10.4s) |   C |    10 | 16.9 |        
    9032 | 2025-03-13 17:05:00 |        MASTER-Tunka | (18h 26m 33.89s , +51d 35m 44.0s) |   C |    10 | 16.8 |        
    9042 | 2025-03-13 17:05:00 |        MASTER-Tunka | (18h 26m 33.90s , +51d 35m 44.3s) |   C |    30 | 17.6 |  Coadd 
    9055 | 2025-03-13 17:05:23 |        MASTER-Tunka | (18h 26m 37.63s , +51d 37m 14.3s) |   C |    10 | 16.9 |        
    9091 | 2025-03-13 17:06:00 |        MASTER-Tunka | (18h 26m 30.94s , +51d 36m 27.3s) |   C |    10 | 16.9 |        
    9113 | 2025-03-13 17:06:21 |        MASTER-Tunka | (18h 26m 31.10s , +51d 37m 28.0s) |   C |    10 | 16.9 |        
    9123 | 2025-03-13 17:06:21 |        MASTER-Tunka | (18h 26m 31.13s , +51d 37m 28.4s) |   C |    30 | 17.5 |  Coadd 
    9138 | 2025-03-13 17:06:46 |        MASTER-Tunka | (18h 26m 37.27s , +51d 36m 28.0s) |   C |    10 | 17.0 |        
    9161 | 2025-03-13 17:07:09 |        MASTER-Tunka | (18h 26m 30.85s , +51d 35m 29.1s) |   C |    10 | 16.9 |        
    9194 | 2025-03-13 17:07:42 |        MASTER-Tunka | (18h 26m 36.43s , +51d 35m 41.8s) |   C |    10 | 16.9 |        
    9204 | 2025-03-13 17:07:42 |        MASTER-Tunka | (18h 26m 36.44s , +51d 35m 41.9s) |   C |    30 | 17.6 |  Coadd 
    9218 | 2025-03-13 17:08:06 |        MASTER-Tunka | (18h 26m 34.84s , +51d 37m 14.2s) |   C |    10 | 16.8 |        
    9240 | 2025-03-13 17:08:28 |        MASTER-Tunka | (18h 26m 34.84s , +51d 35m 31.0s) |   C |    10 | 16.8 |        
    9263 | 2025-03-13 17:08:51 |        MASTER-Tunka | (18h 26m 37.58s , +51d 37m 22.7s) |   C |    10 | 16.8 |        
    9273 | 2025-03-13 17:08:51 |        MASTER-Tunka | (18h 26m 37.55s , +51d 37m 22.5s) |   C |    30 | 17.5 |  Coadd 
    9287 | 2025-03-13 17:09:15 |        MASTER-Tunka | (18h 26m 31.18s , +51d 36m 32.0s) |   C |    10 | 16.9 |        
    9309 | 2025-03-13 17:09:37 |        MASTER-Tunka | (18h 26m 33.16s , +51d 37m 32.2s) |   C |    10 | 16.8 |        
    9331 | 2025-03-13 17:09:59 |        MASTER-Tunka | (18h 26m 38.97s , +51d 36m 31.6s) |   C |    10 | 16.8 |        
    9341 | 2025-03-13 17:09:59 |        MASTER-Tunka | (18h 26m 38.95s , +51d 36m 32.2s) |   C |    30 | 17.4 |  Coadd 
    9369 | 2025-03-13 17:10:38 |        MASTER-Tunka | (18h 26m 32.93s , +51d 35m 33.1s) |   C |    10 | 16.8 |        
    9393 | 2025-03-13 17:11:02 |        MASTER-Tunka | (18h 26m 39.10s , +51d 35m 41.4s) |   C |    10 | 16.8 |        
    9416 | 2025-03-13 17:11:25 |        MASTER-Tunka | (18h 26m 35.66s , +51d 37m 29.0s) |   C |    10 | 16.9 |        
    9426 | 2025-03-13 17:11:25 |        MASTER-Tunka | (18h 26m 35.67s , +51d 37m 29.1s) |   C |    30 | 17.6 |  Coadd 
    9439 | 2025-03-13 17:11:47 |        MASTER-Tunka | (18h 26m 35.80s , +51d 35m 40.3s) |   C |    10 | 16.8 |        
    9461 | 2025-03-13 17:12:09 |        MASTER-Tunka | (18h 26m 38.43s , +51d 37m 27.2s) |   C |    10 | 16.8 |        
    9485 | 2025-03-13 17:12:34 |        MASTER-Tunka | (18h 26m 32.01s , +51d 36m 36.8s) |   C |    10 | 16.9 |        
    9495 | 2025-03-13 17:12:34 |        MASTER-Tunka | (18h 26m 31.99s , +51d 36m 36.9s) |   C |    30 | 17.6 |  Coadd 
    9509 | 2025-03-13 17:12:57 |        MASTER-Tunka | (18h 26m 33.59s , +51d 37m 37.5s) |   C |    10 | 16.9 |        
    9532 | 2025-03-13 17:13:20 |        MASTER-Tunka | (18h 26m 38.97s , +51d 36m 37.6s) |   C |    10 | 16.9 |        
    9558 | 2025-03-13 17:13:46 |        MASTER-Tunka | (18h 26m 32.63s , +51d 35m 37.9s) |   C |    10 | 16.8 |        
    9568 | 2025-03-13 17:13:46 |        MASTER-Tunka | (18h 26m 32.61s , +51d 35m 38.5s) |   C |    30 | 17.6 |  Coadd 
    9587 | 2025-03-13 17:14:15 |        MASTER-Tunka | (18h 26m 39.27s , +51d 35m 40.7s) |   C |    10 | 16.9 |        
    9613 | 2025-03-13 17:14:41 |        MASTER-Tunka | (18h 26m 36.53s , +51d 37m 18.0s) |   C |    10 | 16.8 |        
    9637 | 2025-03-13 17:15:05 |        MASTER-Tunka | (18h 26m 36.60s , +51d 36m 00.4s) |   C |    10 | 16.7 |        
    9647 | 2025-03-13 17:15:05 |        MASTER-Tunka | (18h 26m 36.62s , +51d 36m 00.8s) |   C |    30 | 17.4 |  Coadd 
    9660 | 2025-03-13 17:15:28 |        MASTER-Tunka | (18h 26m 40.68s , +51d 37m 37.4s) |   C |    10 | 16.6 |        
    9681 | 2025-03-13 17:15:50 |        MASTER-Tunka | (18h 26m 33.64s , +51d 36m 41.2s) |   C |    10 | 16.6 |        
    9705 | 2025-03-13 17:16:14 |        MASTER-Tunka | (18h 26m 34.47s , +51d 37m 42.4s) |   C |    10 | 16.7 |        
    9715 | 2025-03-13 17:16:14 |        MASTER-Tunka | (18h 26m 34.48s , +51d 37m 42.4s) |   C |    30 | 17.4 |  Coadd 
    9730 | 2025-03-13 17:16:38 |        MASTER-Tunka | (18h 26m 39.57s , +51d 36m 42.1s) |   C |    10 | 16.8 |        
    9753 | 2025-03-13 17:17:01 |        MASTER-Tunka | (18h 26m 33.48s , +51d 35m 43.6s) |   C |    10 | 16.8 |        
    9783 | 2025-03-13 17:17:31 |        MASTER-Tunka | (18h 26m 39.45s , +51d 35m 47.0s) |   C |    10 | 16.7 |        
    9793 | 2025-03-13 17:17:31 |        MASTER-Tunka | (18h 26m 39.39s , +51d 35m 48.8s) |   C |    30 | 17.5 |  Coadd 
    9805 | 2025-03-13 17:17:53 |        MASTER-Tunka | (18h 26m 37.41s , +51d 37m 20.4s) |   C |    10 | 16.8 |        
    9828 | 2025-03-13 17:18:16 |        MASTER-Tunka | (18h 26m 37.46s , +51d 36m 02.4s) |   C |    10 | 16.8 |        
    9855 | 2025-03-13 17:18:43 |        MASTER-Tunka | (18h 26m 41.32s , +51d 37m 31.8s) |   C |    10 | 16.8 |        
    9865 | 2025-03-13 17:18:43 |        MASTER-Tunka | (18h 26m 41.29s , +51d 37m 33.2s) |   C |    30 | 17.4 |  Coadd 
    9877 | 2025-03-13 17:19:05 |        MASTER-Tunka | (18h 26m 34.82s , +51d 36m 45.9s) |   C |    10 | 16.8 |        
    9904 | 2025-03-13 17:19:32 |        MASTER-Tunka | (18h 26m 33.93s , +51d 37m 47.4s) |   C |    10 | 16.8 |        
    9928 | 2025-03-13 17:19:57 |        MASTER-Tunka | (18h 26m 40.06s , +51d 36m 46.9s) |   C |    10 | 16.9 |        
    9938 | 2025-03-13 17:19:57 |        MASTER-Tunka | (18h 26m 40.07s , +51d 36m 47.3s) |   C |    30 | 17.6 |  Coadd 
    9952 | 2025-03-13 17:20:20 |        MASTER-Tunka | (18h 26m 35.06s , +51d 35m 48.2s) |   C |    10 | 16.9 |        
    9977 | 2025-03-13 17:20:45 |        MASTER-Tunka | (18h 26m 41.26s , +51d 36m 10.4s) |   C |    10 | 16.8 |        
    9999 | 2025-03-13 17:21:07 |        MASTER-Tunka | (18h 26m 38.25s , +51d 37m 36.4s) |   C |    10 | 16.8 |        
   10009 | 2025-03-13 17:21:07 |        MASTER-Tunka | (18h 26m 38.23s , +51d 37m 36.5s) |   C |    30 | 17.5 |  Coadd 
   10021 | 2025-03-13 17:21:29 |        MASTER-Tunka | (18h 26m 38.20s , +51d 36m 19.4s) |   C |    10 | 16.9 |        
   10045 | 2025-03-13 17:21:53 |        MASTER-Tunka | (18h 26m 41.29s , +51d 37m 25.1s) |   C |    10 | 16.8 |        
   10068 | 2025-03-13 17:22:17 |        MASTER-Tunka | (18h 26m 36.40s , +51d 36m 53.4s) |   C |    10 | 16.9 |        
   10078 | 2025-03-13 17:22:17 |        MASTER-Tunka | (18h 26m 36.34s , +51d 36m 52.3s) |   C |    30 | 17.5 |  Coadd 
   10091 | 2025-03-13 17:22:39 |        MASTER-Tunka | (18h 26m 35.75s , +51d 37m 52.4s) |   C |    10 | 16.7 |        
   10118 | 2025-03-13 17:23:06 |        MASTER-Tunka | (18h 26m 42.28s , +51d 36m 52.8s) |   C |    10 | 16.8 |        
   10140 | 2025-03-13 17:23:29 |        MASTER-Tunka | (18h 26m 35.52s , +51d 35m 53.7s) |   C |    10 | 16.8 |        
   10150 | 2025-03-13 17:23:29 |        MASTER-Tunka | (18h 26m 35.53s , +51d 35m 53.4s) |   C |    30 | 17.4 |  Coadd 
   10166 | 2025-03-13 17:23:54 |        MASTER-Tunka | (18h 26m 40.98s , +51d 36m 05.8s) |   C |    10 | 16.8 |        
   10189 | 2025-03-13 17:24:17 |        MASTER-Tunka | (18h 26m 38.98s , +51d 37m 47.3s) |   C |    10 | 16.8 |        
   10211 | 2025-03-13 17:24:39 |        MASTER-Tunka | (18h 26m 39.03s , +51d 36m 22.3s) |   C |    10 | 16.8 |        
   10221 | 2025-03-13 17:24:39 |        MASTER-Tunka | (18h 26m 39.04s , +51d 36m 22.5s) |   C |    30 | 17.4 |  Coadd 
   10235 | 2025-03-13 17:25:03 |        MASTER-Tunka | (18h 26m 41.70s , +51d 37m 38.1s) |   C |    10 | 16.8 |        
   10257 | 2025-03-13 17:25:26 |        MASTER-Tunka | (18h 26m 36.78s , +51d 36m 56.0s) |   C |    10 | 16.8 |        
   10281 | 2025-03-13 17:25:50 |        MASTER-Tunka | (18h 26m 36.93s , +51d 37m 57.5s) |   C |    10 | 16.8 |        
   10291 | 2025-03-13 17:25:50 |        MASTER-Tunka | (18h 26m 36.94s , +51d 37m 57.5s) |   C |    30 | 17.5 |  Coadd 
   10305 | 2025-03-13 17:26:13 |        MASTER-Tunka | (18h 26m 43.13s , +51d 36m 57.2s) |   C |    10 | 16.8 |        
   10329 | 2025-03-13 17:26:38 |        MASTER-Tunka | (18h 26m 37.01s , +51d 35m 58.4s) |   C |    10 | 16.8 |        
   10352 | 2025-03-13 17:27:01 |        MASTER-Tunka | (18h 26m 43.18s , +51d 36m 20.2s) |   C |    10 | 16.8 |        
   10362 | 2025-03-13 17:27:01 |        MASTER-Tunka | (18h 26m 43.20s , +51d 36m 19.9s) |   C |    30 | 17.3 |  Coadd 
   10374 | 2025-03-13 17:27:23 |        MASTER-Tunka | (18h 26m 39.80s , +51d 37m 43.0s) |   C |    10 | 16.8 |        
   10720 | 2025-03-13 17:33:08 |        MASTER-Tunka | (18h 26m 36.56s , +51d 37m 55.9s) |   C |    10 | 16.6 |        
   10744 | 2025-03-13 17:33:32 |        MASTER-Tunka | (18h 26m 42.69s , +51d 36m 56.6s) |   C |    10 | 16.8 |        
   10754 | 2025-03-13 17:33:32 |        MASTER-Tunka | (18h 26m 42.69s , +51d 36m 56.5s) |   C |    30 | 17.5 |  Coadd 
   10767 | 2025-03-13 17:33:55 |        MASTER-Tunka | (18h 26m 37.68s , +51d 35m 57.3s) |   C |    10 | 16.8 |        
   10789 | 2025-03-13 17:34:18 |        MASTER-Tunka | (18h 26m 44.21s , +51d 36m 18.9s) |   C |    10 | 16.8 |        
   10815 | 2025-03-13 17:34:43 |        MASTER-Tunka | (18h 26m 40.39s , +51d 37m 30.3s) |   C |    10 | 16.9 |        
   10825 | 2025-03-13 17:34:43 |        MASTER-Tunka | (18h 26m 40.44s , +51d 37m 30.2s) |   C |    30 | 17.7 |  Coadd 
   10839 | 2025-03-13 17:35:08 |        MASTER-Tunka | (18h 26m 40.46s , +51d 36m 13.0s) |   C |    10 | 16.8 |        
   10862 | 2025-03-13 17:35:30 |        MASTER-Tunka | (18h 26m 43.41s , +51d 37m 50.3s) |   C |    10 | 16.8 |        
   10885 | 2025-03-13 17:35:53 |        MASTER-Tunka | (18h 26m 36.68s , +51d 37m 01.7s) |   C |    10 | 16.9 |        
   10895 | 2025-03-13 17:35:53 |        MASTER-Tunka | (18h 26m 36.66s , +51d 37m 02.1s) |   C |    30 | 17.6 |  Coadd 
   10907 | 2025-03-13 17:36:15 |        MASTER-Tunka | (18h 26m 38.30s , +51d 38m 01.9s) |   C |    10 | 16.9 |        
   10930 | 2025-03-13 17:36:38 |        MASTER-Tunka | (18h 26m 43.27s , +51d 37m 02.6s) |   C |    10 | 16.8 |        
   10953 | 2025-03-13 17:37:01 |        MASTER-Tunka | (18h 26m 38.01s , +51d 36m 02.4s) |   C |    10 | 16.8 |        
   10963 | 2025-03-13 17:37:01 |        MASTER-Tunka | (18h 26m 38.00s , +51d 36m 03.5s) |   C |    30 | 17.6 |  Coadd 
   10976 | 2025-03-13 17:37:24 |        MASTER-Tunka | (18h 26m 44.18s , +51d 36m 19.5s) |   C |    10 | 16.9 |        
   11004 | 2025-03-13 17:37:52 |        MASTER-Tunka | (18h 26m 41.15s , +51d 38m 04.5s) |   C |    10 | 16.8 |        
   11029 | 2025-03-13 17:38:17 |        MASTER-Tunka | (18h 26m 41.16s , +51d 36m 26.7s) |   C |    10 | 16.8 |        
   11039 | 2025-03-13 17:38:17 |        MASTER-Tunka | (18h 26m 41.14s , +51d 36m 27.1s) |   C |    30 | 17.5 |  Coadd 
   11058 | 2025-03-13 17:38:46 |        MASTER-Tunka | (18h 26m 43.88s , +51d 37m 41.9s) |   C |    10 | 16.7 |        
   11205 | 2025-03-13 17:41:14 |        MASTER-Tunka | (18h 26m 39.08s , +51d 38m 10.5s) |   C |    10 | 16.8 |        
   11228 | 2025-03-13 17:41:37 |        MASTER-Tunka | (18h 26m 44.83s , +51d 37m 10.1s) |   C |    10 | 16.8 |        
   11238 | 2025-03-13 17:41:37 |        MASTER-Tunka | (18h 26m 44.80s , +51d 37m 10.9s) |   C |    30 | 17.3 |  Coadd 
   11252 | 2025-03-13 17:42:01 |        MASTER-Tunka | (18h 26m 39.48s , +51d 36m 12.1s) |   C |    10 | 16.8 |        
   11275 | 2025-03-13 17:42:23 |        MASTER-Tunka | (18h 26m 45.26s , +51d 36m 28.7s) |   C |    10 | 16.5 |        
   11299 | 2025-03-13 17:42:47 |        MASTER-Tunka | (18h 26m 42.16s , +51d 37m 46.4s) |   C |    10 | 16.4 |        
   11334 | 2025-03-13 17:42:47 |        MASTER-Tunka | (18h 26m 42.17s , +51d 37m 46.8s) |   C |    80 | 17.2 |  Coadd 
   11323 | 2025-03-13 17:43:11 |        MASTER-Tunka | (18h 26m 42.26s , +51d 36m 16.2s) |   C |    10 | 16.4 |        
   12037 | 2025-03-13 17:55:05 |        MASTER-Tunka | (18h 26m 44.68s , +51d 36m 59.9s) |   C |    10 | 16.9 |        
   12047 | 2025-03-13 17:55:05 |        MASTER-Tunka | (18h 26m 44.69s , +51d 36m 59.7s) |   C |    30 | 17.5 |  Coadd 
   12059 | 2025-03-13 17:55:28 |        MASTER-Tunka | (18h 26m 48.04s , +51d 38m 17.8s) |   C |    10 | 16.8 |        
   12086 | 2025-03-13 17:55:55 |        MASTER-Tunka | (18h 26m 41.99s , +51d 37m 39.3s) |   C |    10 | 16.8 |        
   12201 | 2025-03-13 17:57:25 |        MASTER-Tunka | (18h 26m 42.92s , +51d 38m 41.9s) |   C |    60 | 16.9 |        
   13085 | 2025-03-13 18:12:08 |        MASTER-Tunka | (18h 26m 50.42s , +51d 38m 12.4s) |   C |    60 | 17.1 |        
   13145 | 2025-03-13 18:12:08 |        MASTER-Tunka | (18h 26m 50.39s , +51d 38m 13.0s) |   C |   180 | 18.0 |  Coadd 
   13866 | 2025-03-13 18:25:09 |        MASTER-Tunka | (18h 26m 53.63s , +51d 38m 41.8s) |   C |    60 | 17.3 |        
   13898 | 2025-03-13 18:25:41 |   MASTER-Kislovodsk | (18h 10m 41.76s , +52d 27m 30.9s) |   C |    60 | 15.9 |        
   13989 | 2025-03-13 18:27:12 |   MASTER-Kislovodsk | (18h 23m 41.90s , +52d 26m 09.7s) |   C |    60 | 15.9 |        
   14150 | 2025-03-13 18:29:53 |   MASTER-Kislovodsk | (18h 22m 06.18s , +54d 19m 08.0s) |   C |    60 | 15.5 |        
   14177 | 2025-03-13 18:30:20 |        MASTER-Tunka | (18h 26m 51.05s , +51d 38m 00.9s) |   C |    60 | 17.2 |        
   14489 | 2025-03-13 18:35:33 |        MASTER-Tunka | (18h 26m 49.28s , +51d 40m 07.6s) |   C |    60 | 17.4 |        
   14623 | 2025-03-13 18:37:46 |   MASTER-Kislovodsk | (18h 10m 37.65s , +52d 27m 19.5s) |   C |    60 | 15.8 |        
   14703 | 2025-03-13 18:39:06 |   MASTER-Kislovodsk | (18h 23m 44.86s , +52d 27m 56.3s) |   C |    60 | 15.7 |        
   14811 | 2025-03-13 18:40:54 |        MASTER-Tunka | (18h 26m 56.06s , +51d 38m 22.4s) |   C |    60 | 17.6 |        
   14863 | 2025-03-13 18:41:46 |   MASTER-Kislovodsk | (18h 22m 08.17s , +54d 19m 55.4s) |   C |    60 | 15.9 |        
   15022 | 2025-03-13 18:44:26 |   MASTER-Kislovodsk | (18h 13m 52.92s , +50d 32m 34.5s) |   C |    60 | 15.7 |        
   15102 | 2025-03-13 18:45:45 |   MASTER-Kislovodsk | (18h 26m 30.58s , +50d 33m 17.4s) |   C |    60 | 15.8 |        
   15262 | 2025-03-13 18:48:25 |   MASTER-Kislovodsk | (18h 10m 39.41s , +52d 28m 11.9s) |   C |    60 | 16.3 |        
   15342 | 2025-03-13 18:49:45 |   MASTER-Kislovodsk | (18h 23m 53.56s , +52d 26m 49.5s) |   C |    60 | 15.8 |        
   15501 | 2025-03-13 18:52:24 |   MASTER-Kislovodsk | (18h 22m 15.90s , +54d 20m 16.1s) |   C |    60 | 16.2 |        
   15660 | 2025-03-13 18:55:04 |   MASTER-Kislovodsk | (18h 13m 54.34s , +50d 32m 38.8s) |   C |    60 | 15.9 |

Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.

GCN Circular #39710
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Fermi/LAT GRB 250313A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021822
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 #39711
N. Di Lalla (Stanford Univ.), R. Gupta (NASA GSFC), and M. Arimoto (Kanazawa Univ.) report on behalf of the Fermi-LAT Collaboration:
On March 13, 2025, Fermi-LAT detected high-energy emission from GRB 250313A, which was also detected by Fermi-GBM (trigger 763569278 / 250313607, GCN 39703).
The best LAT on-ground location is found to be:
RA, Dec = 278.53, 53.72 (J2000)
with an error radius of 0.23 deg (90 % containment, statistical error only). This was 1 deg from the LAT boresight at the time of the GBM trigger (T0 = 14:34:33.69 UT).
The data from the Fermi-LAT shows 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 - 1200 s after the GBM trigger is (4.0 ± 0.9) E-6 ph/cm2/s. The estimated photon index above 100 MeV is 2.0 ± 0.2.
The highest-energy photon is a 1.5 GeV event which is observed ~ 27 seconds after the GBM trigger.
A Swift ToO has been approved for this burst.
The Fermi-LAT point of contact for this burst is Makoto Arimoto (arimoto@se.kanazawa-u.ac.jp).
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 #39714
A. Dasgupta (BITS Pilani, Hyderabad), G. Waratkar (IITB), M. Tembhurnikar (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 250313A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 39703) and Fermi/LAT (Lalla et al., GCN Circ. 39711).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-03-13 14:34:39.0 UTC. The measured peak count rate associated with the burst is 1059 (+56, -49) counts/s above the background in the combined data of three quadrants (out of four), with a total of 6772 (+199, -209) counts. The local mean background count rate was 182 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 12 (+1, -1) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-03-13 14:34:42.3 UTC. The measured peak count rate is 2082 (+96, -75) counts/s above the background in the combined Veto data of all quadrants, with a total of 13178 (+422, -439) counts. The local mean background count rate was 1222 (+6, -7) counts/s. We measure a T90 of 10 (+1, -1) 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
GCN Circular #39716
SVOM/GRM team: Chen-Wei Wang, Wen-Jun Tan, Yan-Qiu Zhang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Bertrand Cordier, Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP), Frédéric Piron (LUPM)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 250313A (SVOM trigger reference: sb25031306) at 2025-03-13T14:34:33.900 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #39703), AstroSat (A. Dasgupta et al., GCN #39714) and Fermi/LAT (N. Di Lalla et al., GCN #39711).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a main emission followed by a flare with a T90 of 310.8 +3.4/-6.6 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250313A.png
ECLAIRs was not collecting data at the time of this burst.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang@ihep.ac.cn)
GCN Circular #39721
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The long GRB 250313A (Fermi-GBM detection: Fermi GBM team, GCN 39703; BALROG localization: Preis & Greiner, GCN 39704; Fermi-LAT detection: Di Lalla et al., GCN 39711; AstroSat CZTI detection: Dasgupta et al., GCN 39714; SVOM/GRM observation: Wang et al., GCN 39716) triggered Konus-Wind (KW) at T0=52473.618 s UT (14:34:33.618).
The burst light curve shows a bright, multi-peaked emission pulse, with the duration of ~15 s, followed by a broad, weaker pulse, peaked at T0+270 s. The total duration of the burst is ~345 s. The emission is seen up to ~1.5 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250313_T52473/
As observed by Konus-Wind, the burst had a fluence of (1.06 ± 0.19)x10^-4 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 7.936 s, of (1.23 ± 0.10)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+345 s) is best fit in the 20 keV - 1.5 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -1.13 (-0.04,+0.04), the high energy photon index beta = -2.64 (-0.73,+0.21), the peak energy Ep = 237 (-15,+18) keV, chi2 = 34/63 dof.
The spectrum near the peak count rate (measured from T0+7.936 s to T0+8.960 s) is best fit in the 20 keV - 1.5 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.52 (-0.07,+0.08), the high energy photon index beta = -2.80 (-0.41,+0.25), the peak energy Ep = 294 (-20,+21) keV, chi2 = 34/51 dof.
All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.

GCN Circular #39723
M. A. Williams (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU) 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 250313A, collecting 6.3 ks of Photon Counting (PC) mode data between T0+30.7 ks and T0+82.7 ks.
Seven 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):  278.5986  =  18:34:23.66
  Dec (J2000.0): +53.8117  =  +53:48:42.1
  Error: 5.7 arcsec (radius, 90% conf.)
  Count-rate: (3.20 [+1.07, -0.89])e-3 ct s^-1	 
  Distance: 360 arcsec from Fermi/LAT position.
  Flux: (1.13 [+0.38, -0.32])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:

  RA (J2000.0):  278.4773  =  18:33:54.54
  Dec (J2000.0): +53.6792  =  +53:40:45.1
  Error: 5.9 arcsec (radius, 90% conf.)
  Count-rate: (1.23 [+0.71, -0.54])e-3 ct s^-1	 
  Distance: 184 arcsec from Fermi/LAT position.
  Flux: (5.1 [+2.9, -2.2])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 3:

  RA (J2000.0):  278.7435  =  18:34:58.45
  Dec (J2000.0): +53.8112  =  +53:48:40.2
  Error: 6.1 arcsec (radius, 90% conf.)
  Count-rate: (1.19 [+0.90, -0.67])e-3 ct s^-1	 
  Distance: 560 arcsec from Fermi/LAT position.
  Flux: (2.6 [+2.0, -1.5])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 4:

  RA (J2000.0):  278.7131  =  18:34:51.13
  Dec (J2000.0): +53.8208  =  +53:49:14.7
  Error: 6.9 arcsec (radius, 90% conf.)
  Count-rate: (2.16 [+0.95, -0.76])e-3 ct s^-1	 
  Distance: 532 arcsec from Fermi/LAT position.
  Flux: (2.38 [+1.04, -0.83])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 5:

  RA (J2000.0):  278.5290  =  18:34:6.96
  Dec (J2000.0): +53.8678  =  +53:52:04.2
  Error: 8.1 arcsec (radius, 90% conf.)
  Count-rate: (1.57 [+0.84, -0.65])e-3 ct s^-1	 
  Distance: 532 arcsec from Fermi/LAT position.
  Flux: (6.4 [+3.4, -2.6])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 6:

  RA (J2000.0):  278.5496  =  18:34:11.90
  Dec (J2000.0): +53.7202  =  +53:43:12.8
  Error: 5.7 arcsec (radius, 90% conf.)
  Count-rate: (1.35 [+0.73, -0.55])e-3 ct s^-1	 
  Distance: 41 arcsec from Fermi/LAT position.
  Flux: (8.6 [+4.7, -3.5])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 7:

  RA (J2000.0):  278.6648  =  18:34:39.55
  Dec (J2000.0): +53.6612  =  +53:39:40.2
  Error: 7.4 arcsec (radius, 90% conf.)
  Count-rate: (7.5 [+6.0, -4.6])e-4 ct s^-1   
  Distance: 356 arcsec from Fermi/LAT position.

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/00021822.
This circular is an official product of the Swift-XRT team.

GCN Circular #39725
K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration:
The CALET Gamma-ray Burst Monitor (CGBM) was triggered by GRB 250313A at 14:34:30.53 UTC on 13 March 2025, which is also detected by Fermi-GBM
```
(Fermi-GBM team, GCN #39703), Fermi-LAT (Di Lalla et al., GCN #39711),
AstroSat CZTI (Dasgupta et al., GCN #39714), SVOM/GRM (Wang et al, GCN #39716)
```
and Konus-Wind (Frederiks et al., GCN #39721). (https://cgbm.calet.jp/cgbm_trigger/flight/1425911606/index.html). The burst signal was seen by all CGBM detectors.
The burst light curve shows a multi-peaked structure that starts at T+3.1 sec, peaks at T+11.3 sec, and ends at T+17.4 sec. The T90 and T50 durations measured by the SGM data are 10.1 +/- 0.5 sec and 4.8 +/- 0.3 sec (40-1000 keV), respectively.
The ground-processed light curve is available at
https://cgbm.calet.jp/cgbm_trigger/ground/1425911606/
The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University.
GCN Circular #39726
Eliza Neights (George Washington University, NASA Goddard Space Flight Center), M. Godwin (UAH), C. Meegan (UAH) and O.J. Roberts (USRA) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 14:34:33.69 UT on 13 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250313A (trigger 763569278/250313607), which was also detected by Fermi LAT (Di Lalla et al. 2025, GCN 39711), AstroSat CZTI (Dasgupta et al. 2025, GCN 39714), SVOM/GRM (Wang et al. 2025, GCN 39716), and Konus-Wind (Frederiks et al. 2025, GCN 39721).
The Fermi GBM Final Position location is consistent with the Fermi LAT position.
The angle from the Fermi LAT boresight is 4 degrees.
The GBM light curve consists of two emission episodes, a bright pulse lasting 12 s after the trigger time and a dimmer pulse about 280 s later. The duration (T90) is about 295.2 s (50-300 keV). The time-averaged spectrum from T0-2.2 to T0+389.0 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.36 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 320 +/- 20 keV.
The event fluence (10-1000 keV) in this time interval is (9.4 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+4.7 s in the 10-1000 keV band is 55.4 +/- 0.5 ph/s/cm^2.
The spectrum is fit about equally well by a Band function with Epeak = 280 +/- 20 keV, alpha = -1.34 +/- 0.02, and beta = -2.23 +/- 0.13.
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 #39786
M. Duriskova, 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, L. Szakszonova, 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 long-duration GRB 250313A (FERMI/GBM: GCN Circular 39703, FERMI/LAT: GCN Circular 39711, AstroSat/CZTI: GCN Circular 39714, SVOM/GRM: GCN Circular 39716, Konus-Wind: GCN Circular 39721, CALET/CGBM: GCN Circular 39725) 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 2025-03-13 14:34:41.7 UTC. The T90 duration measured by GRBAlpha is 13 s and the overall significance during T90 reaches 52.3 sigma.
The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250313A_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.

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Jochen Greiner, last update: 19-Mar-2025 [Disclaimer]