TITLE: GCN CIRCULAR NUMBER: 40317 SUBJECT: Fermi GRB 250502B: Global MASTER-Net observations report DATE: 25/05/02 11:31:09 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 GRB 250502B ( Fermi GBM team, GCN 40314) errorbox 74 sec after notice time and 110 sec after trigger time at 2025-05-02 10:15:44 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenith distance = 44 deg. The sun altitude is -11.2 deg.

The galactic latitude b = -18 deg., longitude l = 61 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2858681

We obtain a following upper limits.

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

121 | 2025-05-02 10:15:44 | MASTER-OAFA | (20h 40m 38.20s , +13d 02m 12.4s) | C | 20 | 17.2 | 121 | 2025-05-02 10:15:44 | MASTER-OAFA | (20h 49m 58.93s , +13d 25m 00.9s) | C | 20 | 18.3 | 155 | 2025-05-02 10:16:23 | MASTER-OAFA | (20h 40m 37.90s , +13d 02m 09.6s) | C | 10 | 16.9 | 166 | 2025-05-02 10:16:23 | MASTER-OAFA | (20h 49m 58.55s , +13d 24m 57.5s) | C | 30 | 18.4 | 205 | 2025-05-02 10:17:07 | MASTER-OAFA | (20h 43m 52.56s , +13d 09m 28.3s) | C | 20 | 17.2 | 215 | 2025-05-02 10:17:08 | MASTER-OAFA | (20h 53m 13.53s , +13d 32m 15.9s) | C | 40 | 18.4 | 256 | 2025-05-02 10:17:54 | MASTER-OAFA | (20h 43m 52.15s , +13d 09m 25.1s) | C | 30 | 17.2 | 266 | 2025-05-02 10:17:54 | MASTER-OAFA | (20h 53m 13.16s , +13d 32m 11.9s) | C | 50 | 18.3 | 317 | 2025-05-02 10:18:50 | MASTER-OAFA | (20h 43m 51.68s , +13d 09m 20.3s) | C | 40 | 17.2 | 328 | 2025-05-02 10:18:50 | MASTER-OAFA | (20h 53m 12.71s , +13d 32m 06.8s) | C | 60 | 18.2 | 388 | 2025-05-02 10:19:56 | MASTER-OAFA | (20h 43m 51.16s , +13d 09m 15.6s) | C | 50 | 17.1 | 399 | 2025-05-02 10:19:56 | MASTER-OAFA | (20h 53m 12.22s , +13d 32m 01.2s) | C | 70 | 18.0 | 474 | 2025-05-02 10:21:12 | MASTER-OAFA | (20h 43m 50.52s , +13d 09m 08.5s) | C | 70 | 17.0 | 581 | 2025-05-02 10:22:48 | MASTER-OAFA | (20h 43m 49.65s , +13d 08m 59.4s) | C | 90 | 16.8 | 715 | 2025-05-02 10:24:52 | MASTER-OAFA | (20h 39m 05.67s , +13d 52m 50.6s) | C | 110 | 16.6 | 828 | 2025-05-02 10:27:21 | MASTER-OAFA | (20h 36m 00.38s , +11d 56m 35.1s) | C | 40 | 16.4 | Filter C is a clear (unfiltred) band.

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

View this GCN Circular online at https://gcn.nasa.gov/circulars/40317. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...