GRB 260516C
GCN Circular 44651
Subject
Fermi GRB 260516C: Global MASTER-Net observations report
Date
2026-05-16T22:15:42Z (13 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
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 260516C ( Fermi GBM team, GCN 44648) errorbox 31 sec after notice time and 63 sec after trigger time at 2026-05-16 19:35:42 UT, with upper limit up to 18.7 mag. The observations began at zenith distance = 27 deg. The sun altitude is -48.6 deg.
The galactic latitude b = 1 deg., longitude l = 293 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3319181
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
68 | 2026-05-16 19:35:42 | MASTER-SAAO | (11h 28m 29.01s , -56d 15m 46.9s) | C | 10 | 17.3 |
68 | 2026-05-16 19:35:42 | MASTER-SAAO | (11h 31m 55.60s , -56d 31m 08.1s) | C | 10 | 17.5 |
102 | 2026-05-16 19:36:11 | MASTER-SAAO | (11h 28m 28.89s , -56d 15m 46.7s) | C | 20 | 17.7 |
102 | 2026-05-16 19:36:11 | MASTER-SAAO | (11h 31m 55.42s , -56d 31m 08.1s) | C | 20 | 18.0 |
155 | 2026-05-16 19:36:58 | MASTER-SAAO | (11h 22m 44.28s , -59d 38m 52.0s) | C | 30 | 17.1 |
200 | 2026-05-16 19:36:58 | MASTER-SAAO | (11h 22m 44.28s , -59d 38m 52.0s) | C | 120 | 17.4 |
155 | 2026-05-16 19:36:58 | MASTER-SAAO | (11h 26m 31.14s , -59d 54m 11.9s) | C | 30 | 17.4 |
200 | 2026-05-16 19:36:58 | MASTER-SAAO | (11h 26m 31.15s , -59d 54m 11.8s) | C | 120 | 17.8 |
209 | 2026-05-16 19:37:47 | MASTER-SAAO | (11h 22m 44.18s , -59d 38m 51.3s) | C | 40 | 17.1 |
209 | 2026-05-16 19:37:47 | MASTER-SAAO | (11h 26m 31.02s , -59d 54m 11.2s) | C | 40 | 17.5 |
273 | 2026-05-16 19:38:46 | MASTER-SAAO | (11h 22m 44.06s , -59d 38m 50.3s) | C | 50 | 17.1 |
273 | 2026-05-16 19:38:46 | MASTER-SAAO | (11h 26m 30.89s , -59d 54m 10.4s) | C | 50 | 17.5 |
347 | 2026-05-16 19:39:55 | MASTER-SAAO | (11h 22m 43.88s , -59d 38m 48.6s) | C | 60 | 17.3 |
347 | 2026-05-16 19:39:55 | MASTER-SAAO | (11h 26m 30.80s , -59d 54m 08.8s) | C | 60 | 17.6 |
626 | 2026-05-16 19:44:34 | MASTER-SAAO | (11h 24m 24.54s , -59d 37m 32.6s) | C | 60 | 17.4 |
686 | 2026-05-16 19:44:34 | MASTER-SAAO | (11h 24m 24.54s , -59d 37m 32.6s) | C | 180 | 17.5 |
626 | 2026-05-16 19:44:34 | MASTER-SAAO | (11h 28m 06.66s , -59d 53m 08.5s) | C | 60 | 17.7 |
686 | 2026-05-16 19:44:34 | MASTER-SAAO | (11h 28m 06.70s , -59d 53m 08.6s) | C | 180 | 17.9 |
705 | 2026-05-16 19:45:53 | MASTER-SAAO | (11h 24m 24.42s , -59d 37m 32.0s) | C | 60 | 17.4 |
705 | 2026-05-16 19:45:53 | MASTER-SAAO | (11h 28m 06.55s , -59d 53m 07.8s) | C | 60 | 17.6 |
784 | 2026-05-16 19:47:13 | MASTER-SAAO | (11h 24m 24.31s , -59d 37m 30.4s) | C | 60 | 17.4 |
784 | 2026-05-16 19:47:13 | MASTER-SAAO | (11h 28m 06.41s , -59d 53m 06.3s) | C | 60 | 17.6 |
863 | 2026-05-16 19:48:31 | MASTER-SAAO | (11h 24m 24.22s , -59d 37m 28.7s) | C | 60 | 17.3 |
863 | 2026-05-16 19:48:31 | MASTER-SAAO | (11h 28m 06.25s , -59d 53m 04.6s) | C | 60 | 17.6 |
1850 | 2026-05-16 20:04:28 | MASTER-SAAO | (11h 24m 04.79s , -59d 36m 36.8s) | C | 120 | 17.5 |
1850 | 2026-05-16 20:04:28 | MASTER-SAAO | (11h 27m 46.76s , -59d 52m 15.2s) | C | 120 | 17.8 |
2004 | 2026-05-16 20:07:02 | MASTER-SAAO | (11h 37m 54.80s , -59d 44m 27.2s) | C | 120 | 17.6 |
2004 | 2026-05-16 20:07:02 | MASTER-SAAO | (11h 41m 37.73s , -60d 00m 05.4s) | C | 120 | 17.8 |
2157 | 2026-05-16 20:09:35 | MASTER-SAAO | (11h 37m 55.16s , -59d 43m 25.3s) | C | 120 | 17.6 |
2157 | 2026-05-16 20:09:35 | MASTER-SAAO | (11h 41m 37.91s , -59d 59m 03.3s) | C | 120 | 17.9 |
2310 | 2026-05-16 20:12:09 | MASTER-SAAO | (11h 37m 59.95s , -59d 44m 22.1s) | C | 120 | 17.6 |
2310 | 2026-05-16 20:12:09 | MASTER-SAAO | (11h 41m 42.75s , -60d 00m 00.1s) | C | 120 | 17.8 |
2463 | 2026-05-16 20:14:41 | MASTER-SAAO | (11h 38m 07.66s , -57d 45m 21.9s) | C | 120 | 18.2 |
2463 | 2026-05-16 20:14:41 | MASTER-SAAO | (11h 41m 38.03s , -58d 01m 00.6s) | C | 120 | 18.5 |
2616 | 2026-05-16 20:17:15 | MASTER-SAAO | (11h 38m 13.31s , -57d 45m 08.0s) | C | 120 | 18.2 |
2616 | 2026-05-16 20:17:15 | MASTER-SAAO | (11h 41m 43.61s , -58d 00m 46.9s) | C | 120 | 18.5 |
2769 | 2026-05-16 20:19:47 | MASTER-SAAO | (11h 38m 10.50s , -57d 43m 18.7s) | C | 120 | 18.2 |
2769 | 2026-05-16 20:19:47 | MASTER-SAAO | (11h 41m 40.63s , -57d 58m 57.8s) | C | 120 | 18.5 |
2922 | 2026-05-16 20:22:21 | MASTER-SAAO | (11h 22m 13.66s , -57d 44m 42.9s) | C | 120 | 17.7 |
2922 | 2026-05-16 20:22:21 | MASTER-SAAO | (11h 25m 44.03s , -58d 00m 21.7s) | C | 120 | 17.9 |
3076 | 2026-05-16 20:24:54 | MASTER-SAAO | (11h 22m 15.81s , -57d 42m 54.4s) | C | 120 | 17.8 |
3076 | 2026-05-16 20:24:54 | MASTER-SAAO | (11h 25m 46.05s , -57d 58m 33.5s) | C | 120 | 18.0 |
3229 | 2026-05-16 20:27:28 | MASTER-SAAO | (11h 22m 10.17s , -57d 43m 35.0s) | C | 120 | 17.8 |
3229 | 2026-05-16 20:27:28 | MASTER-SAAO | (11h 25m 40.54s , -57d 59m 14.2s) | C | 120 | 18.0 |
3383 | 2026-05-16 20:30:01 | MASTER-SAAO | (11h 13m 44.65s , -61d 42m 13.8s) | C | 120 | 18.2 |
3383 | 2026-05-16 20:30:01 | MASTER-SAAO | (11h 17m 41.85s , -61d 57m 51.5s) | C | 120 | 18.6 |
3536 | 2026-05-16 20:32:34 | MASTER-SAAO | (11h 13m 50.07s , -61d 43m 09.6s) | C | 120 | 18.2 |
3536 | 2026-05-16 20:32:34 | MASTER-SAAO | (11h 17m 47.42s , -61d 58m 47.3s) | C | 120 | 18.7 |
3689 | 2026-05-16 20:35:07 | MASTER-SAAO | (11h 13m 44.81s , -61d 44m 05.2s) | C | 120 | 18.2 |
3689 | 2026-05-16 20:35:07 | MASTER-SAAO | (11h 17m 42.30s , -61d 59m 42.9s) | C | 120 | 18.7 |
3842 | 2026-05-16 20:37:41 | MASTER-SAAO | (11h 24m 03.00s , -59d 37m 40.6s) | C | 120 | 17.5 |
3842 | 2026-05-16 20:37:41 | MASTER-SAAO | (11h 27m 45.41s , -59d 53m 19.5s) | C | 120 | 17.6 |
3995 | 2026-05-16 20:40:14 | MASTER-SAAO | (11h 23m 59.91s , -59d 35m 52.6s) | C | 120 | 17.5 |
3995 | 2026-05-16 20:40:14 | MASTER-SAAO | (11h 27m 42.09s , -59d 51m 31.5s) | C | 120 | 17.6 |
4149 | 2026-05-16 20:42:48 | MASTER-SAAO | (11h 23m 59.68s , -59d 37m 31.9s) | C | 120 | 17.5 |
4149 | 2026-05-16 20:42:48 | MASTER-SAAO | (11h 27m 42.06s , -59d 53m 11.0s) | C | 120 | 17.6 |
4303 | 2026-05-16 20:45:21 | MASTER-SAAO | (11h 24m 02.31s , -59d 35m 54.7s) | C | 120 | 17.5 |
4303 | 2026-05-16 20:45:21 | MASTER-SAAO | (11h 27m 44.51s , -59d 51m 33.8s) | C | 120 | 17.6 |
4456 | 2026-05-16 20:47:54 | MASTER-SAAO | (11h 27m 39.44s , -59d 52m 02.8s) | C | 120 | 17.6 |
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 Circular 44648
Subject
GRB 260516C: Fermi GBM Final Real-time Localization
Date
2026-05-16T19:45:10Z (13 days 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 19:34:38 UT on 16 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260516C (trigger 800652883.931176 / 260516816).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 172.6, Dec = -59.9 (J2000 degrees, equivalent to J2000 11h 30m, -59d 53'), with a statistical uncertainty of 3.2 degrees.
The angle from the Fermi LAT boresight is 36.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516816/quicklook/glg_skymap_all_bn260516816.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/bn260516816/quicklook/glg_healpix_all_bn260516816.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260516816/quicklook/glg_lc_medres34_bn260516816.gif