GCN 43921: Fermi GRB 260305A: Global MASTER-Net observations report
2026-03-05T03:00:46.288Z | rev 0
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO),
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 [1] located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260305A ( Fermi GBM team, GCN 43920) errorbox 55 sec after notice time and 87 sec after trigger time at 2026-03-05 02:43:05 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 70 deg. The sun altitude is -22.7 deg.
The galactic latitude b = 68 deg., longitude l = 57 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3169780
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
98 | 2026-03-05 02:43:05 | MASTER-SAAO | (14h 27m 04.56s , +37d 55m 52.3s) | C | 20 | 17.2 |
98 | 2026-03-05 02:43:05 | MASTER-SAAO | (14h 24m 55.60s , +38d 11m 54.7s) | C | 20 | 17.0 |
217 | 2026-03-05 02:44:55 | MASTER-SAAO | (14h 12m 08.18s , +34d 56m 29.5s) | C | 40 | 17.4 |
272 | 2026-03-05 02:44:55 | MASTER-SAAO | (14h 12m 08.18s , +34d 56m 29.4s) | C | 150 | 18.6 |
217 | 2026-03-05 02:44:55 | MASTER-SAAO | (14h 14m 11.70s , +34d 40m 22.7s) | C | 40 | 17.6 |
272 | 2026-03-05 02:44:55 | MASTER-SAAO | (14h 14m 11.71s , +34d 40m 22.8s) | C | 150 | 18.4 |
281 | 2026-03-05 02:45:54 | MASTER-SAAO | (14h 14m 11.94s , +34d 40m 26.1s) | C | 50 | 17.8 |
281 | 2026-03-05 02:45:54 | MASTER-SAAO | (14h 12m 08.41s , +34d 56m 34.1s) | C | 50 | 17.5 |
355 | 2026-03-05 02:47:03 | MASTER-SAAO | (14h 12m 08.69s , +34d 56m 39.2s) | C | 60 | 17.7 |
355 | 2026-03-05 02:47:03 | MASTER-SAAO | (14h 14m 12.16s , +34d 40m 30.0s) | C | 60 | 17.8 |
625 | 2026-03-05 02:51:33 | MASTER-SAAO | (14h 24m 26.43s , +33d 57m 36.0s) | C | 60 | 17.8 |
625 | 2026-03-05 02:51:33 | MASTER-SAAO | (14h 22m 22.92s , +34d 13m 45.5s) | C | 60 | 17.5 |
704 | 2026-03-05 02:52:52 | MASTER-SAAO | (14h 24m 26.68s , +33d 57m 40.9s) | C | 60 | 17.8 |
704 | 2026-03-05 02:52:52 | MASTER-SAAO | (14h 22m 23.24s , +34d 13m 52.3s) | C | 60 | 17.7 |
784 | 2026-03-05 02:54:11 | MASTER-SAAO | (14h 22m 23.58s , +34d 13m 57.5s) | C | 60 | 17.7 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp.
http : // www.pereplet.ru/lipunov/625.html
GCN 43920: GRB 260305A: Fermi GBM Final Real-time Localization
2026-03-05T02:52:09.478Z | rev 0
The Fermi GBM team reports the detection of a likely LONG GRB
At 02:41:38 UT on 5 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260305A (trigger 794371303.18619 / 260305112).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 216.5, Dec = 34.0 (J2000 degrees, equivalent to J2000 14h 26m, 34d 00'), with a statistical uncertainty of 2.4 degrees.
The angle from the Fermi LAT boresight is 49.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260305112/quicklook/glg_skymap_all_bn260305112.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260305112/quicklook/glg_healpix_all_bn260305112.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260305112/quicklook/glg_lc_medres34_bn260305112.gif