TITLE: GCN CIRCULAR NUMBER: 41149 SUBJECT: Fermi trigger No 775101099: Global MASTER-Net observations report DATE: 25/07/25 02:00:36 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs lipunov@xray.sai.msu.ru

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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB250725.08 (trigger No 775101099,02h 08m 43.20s , -85d 24m 00.0s, R=1.74) errorbox 13 sec after notice time and 47 sec after trigger time at 2025-07-25 01:52:22 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 64 deg. The sun altitude is -50.5 deg.

MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB250725.08 errorbox 20 sec after notice time and 54 sec after trigger time at 2025-07-25 01:52:29 UT, with upper limit up to 17.0 mag. The observations began at zenith distance = 53 deg. The sun altitude is -46.5 deg.

The galactic latitude b = -32 deg., longitude l = 301 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2947370

We obtain a following upper limits.

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

52 | 2025-07-25 01:52:22 | MASTER-OAFA | (02h 25m 24.07s , -83d 05m 36.9s) | C | 10 | 18.2 | 60 | 2025-07-25 01:52:29 | MASTER-SAAO | (02h 09m 37.42s , -82d 51m 47.1s) | P/ | 10 | 16.1 | 60 | 2025-07-25 01:52:29 | MASTER-SAAO | (02h 24m 15.37s , -83d 06m 32.9s) | P\ | 10 | 16.5 | 68 | 2025-07-25 01:52:38 | MASTER-OAFA | (02h 25m 23.82s , -83d 05m 36.2s) | C | 10 | 18.3 | 89 | 2025-07-25 01:52:54 | MASTER-OAFA | (02h 25m 23.31s , -83d 05m 34.7s) | C | 20 | 18.7 | 94 | 2025-07-25 01:52:58 | MASTER-SAAO | (02h 09m 37.12s , -82d 51m 49.2s) | P/ | 20 | 16.8 | 94 | 2025-07-25 01:52:58 | MASTER-SAAO | (02h 24m 15.31s , -83d 06m 34.5s) | P\ | 20 | 17.0 | 116 | 2025-07-25 01:53:20 | MASTER-OAFA | (02h 25m 22.79s , -83d 05m 34.2s) | C | 20 | 18.7 | 133 | 2025-07-25 01:53:37 | MASTER-SAAO | (02h 24m 14.91s , -83d 06m 36.1s) | P\ | 20 | 17.0 | 147 | 2025-07-25 01:53:46 | MASTER-OAFA | (02h 25m 21.97s , -83d 05m 32.7s) | C | 30 | 19.0 | 183 | 2025-07-25 01:54:22 | MASTER-OAFA | (02h 25m 21.21s , -83d 05m 31.3s) | C | 30 | 19.0 | Filter C is a clear (unfiltred) band.

The observation and reduction will continue. The message may be cited.

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