GRB 250406A
GCN Circular 40094
Subject
GRB 250406A: Fermi GBM Final Real-time Localization
Date
2025-04-06T14:48:42Z (2 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 LONG GRB
At 14:38:11 UT on 6 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250406A (trigger 765643096.56557 / 250406610).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 6.2, Dec = -63.2 (J2000 degrees, equivalent to J2000 00h 24m, -63d 12'), with a statistical uncertainty of 1.0 degrees.
The angle from the Fermi LAT boresight is 29.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250406610/quicklook/glg_skymap_all_bn250406610.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/bn250406610/quicklook/glg_healpix_all_bn250406610.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250406610/quicklook/glg_lc_medres34_bn250406610.gif
GCN Circular 40096
Subject
Fermi GRB 250406A: Global MASTER-Net observations report
Date
2025-04-06T18:15:59Z (2 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250406A ( Fermi GBM team, GCN 40094) errorbox 9143 sec after notice time and 9171 sec after trigger time at 2025-04-06 17:11:03 UT, with upper limit up to 18.1 mag. Observations started at twilight. The observations began at zenith distance = 68 deg. The sun altitude is -9.9 deg.
The galactic latitude b = -54 deg., longitude l = 308 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2834949
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
9202 | 2025-04-06 17:11:03 | MASTER-SAAO | (00h 25m 46.55s , -63d 33m 50.2s) | C | 60 | 16.6 |
9281 | 2025-04-06 17:12:22 | MASTER-SAAO | (00h 43m 35.96s , -63d 32m 39.4s) | C | 60 | 16.8 |
9360 | 2025-04-06 17:13:41 | MASTER-SAAO | (00h 24m 01.48s , -61d 38m 12.8s) | C | 60 | 16.8 |
9439 | 2025-04-06 17:15:01 | MASTER-SAAO | (00h 40m 43.37s , -61d 39m 07.2s) | C | 60 | 17.0 |
9519 | 2025-04-06 17:16:20 | MASTER-SAAO | (00h 27m 48.66s , -65d 26m 57.7s) | C | 60 | 17.2 |
9803 | 2025-04-06 17:21:04 | MASTER-SAAO | (00h 09m 41.55s , -63d 33m 51.5s) | C | 60 | 17.6 |
9889 | 2025-04-06 17:22:30 | MASTER-SAAO | (00h 25m 49.55s , -63d 32m 19.4s) | C | 60 | 17.7 |
10129 | 2025-04-06 17:26:30 | MASTER-SAAO | (00h 43m 41.72s , -63d 33m 01.9s) | C | 60 | 17.9 |
10209 | 2025-04-06 17:27:50 | MASTER-SAAO | (00h 23m 59.75s , -61d 39m 57.8s) | C | 60 | 17.7 |
10289 | 2025-04-06 17:29:10 | MASTER-SAAO | (00h 40m 51.41s , -61d 39m 35.0s) | C | 60 | 17.9 |
10368 | 2025-04-06 17:30:29 | MASTER-SAAO | (00h 27m 50.49s , -65d 25m 58.4s) | C | 60 | 17.8 |
10653 | 2025-04-06 17:35:14 | MASTER-SAAO | (00h 09m 43.11s , -63d 32m 50.4s) | C | 60 | 18.0 |
10733 | 2025-04-06 17:36:34 | MASTER-SAAO | (00h 25m 48.42s , -63d 31m 49.8s) | C | 60 | 17.9 |
10812 | 2025-04-06 17:37:53 | MASTER-SAAO | (00h 43m 45.24s , -63d 32m 51.2s) | C | 60 | 18.1 |
10892 | 2025-04-06 17:39:13 | MASTER-SAAO | (00h 24m 03.87s , -61d 39m 50.1s) | C | 60 | 17.9 |
10971 | 2025-04-06 17:40:32 | MASTER-SAAO | (00h 40m 54.53s , -61d 39m 38.8s) | C | 60 | 17.8 |
11051 | 2025-04-06 17:41:52 | MASTER-SAAO | (00h 27m 55.06s , -65d 25m 49.8s) | C | 60 | 17.8 |
11335 | 2025-04-06 17:46:36 | MASTER-SAAO | (00h 09m 48.00s , -63d 32m 47.3s) | C | 60 | 17.8 |
11415 | 2025-04-06 17:47:56 | MASTER-SAAO | (00h 25m 51.70s , -63d 31m 45.0s) | C | 60 | 17.9 |
11494 | 2025-04-06 17:49:15 | MASTER-SAAO | (00h 43m 49.94s , -63d 32m 44.3s) | C | 60 | 17.9 |
11574 | 2025-04-06 17:50:35 | MASTER-SAAO | (00h 24m 06.65s , -61d 39m 45.5s) | C | 60 | 17.9 |
11653 | 2025-04-06 17:51:54 | MASTER-SAAO | (00h 40m 58.05s , -61d 39m 30.5s) | C | 60 | 17.9 |
12144 | 2025-04-06 18:00:05 | MASTER-SAAO | (00h 28m 06.48s , -65d 25m 50.6s) | C | 60 | 17.9 |
12430 | 2025-04-06 18:04:52 | MASTER-SAAO | (00h 10m 03.09s , -63d 32m 45.1s) | C | 60 | 17.8 |
12510 | 2025-04-06 18:06:11 | MASTER-SAAO | (00h 25m 59.78s , -63d 33m 39.9s) | C | 60 | 17.8 |
12589 | 2025-04-06 18:07:30 | MASTER-SAAO | (00h 43m 57.06s , -63d 33m 07.7s) | C | 60 | 17.9 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 40100
Subject
GRB 250406A: AstroSat CZTI detection
Date
2025-04-07T04:27:16Z (2 months ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
M. Tembhurnikar (IUCAA), G. Waratkar (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 long duration GRB 250406A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40094).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-06 14:38:19.0 UTC. The measured peak count rate associated with the burst is 126 (+25, -17) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1195 (+285, -117) counts. The local mean background count rate was 226 (+1, -6) counts/s. Using cumulative rates, we measure a T90 of 17 (+4, -2) 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 2025-04-06 14:38:17.9 UTC. The measured peak count rate associated with the burst is 329 (+70, -44) counts/s above the background in the combined data of all quadrants, with a total of 2697 (+493, -543) counts. The local mean background count rate was 1320 (+7, -8) counts/s. We measure a T90 of 16 (+5, -5) 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