TITLE: GCN CIRCULAR NUMBER: 40196 SUBJECT: IceCube Alert 250421.71: Global MASTER-Net observations report DATE: 25/04/22 00:39:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs lipunov@xray.sai.msu.ru

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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the IceCube Alert 250421.71 (trigger No 2517159,16h 02m 52.80s , +28d 41m 24.0s, R=1.29) errorbox 21082 sec after notice time and 21147 sec after trigger time at 2025-04-21 22:58:35 UT, with upper limit up to 18.5 mag. The observations began at zenith distance = 15 deg. The sun altitude is -29.5 deg.

The galactic latitude b = 48 deg., longitude l = 47 deg.

Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2849038

We obtain a following upper limits.

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

21177 | 2025-04-21 22:58:35 | MASTER-Kislovodsk | (15h 56m 30.81s , +28d 05m 01.6s) | C | 60 | 18.3 | 21275 | 2025-04-21 23:00:13 | MASTER-Kislovodsk | (16h 05m 26.91s , +28d 03m 52.9s) | C | 60 | 18.5 | 21369 | 2025-04-21 23:01:47 | MASTER-Kislovodsk | (15h 56m 32.92s , +29d 59m 34.7s) | C | 60 | 18.4 | 21452 | 2025-04-21 23:03:10 | MASTER-Kislovodsk | (16h 01m 36.09s , +28d 57m 32.8s) | C | 60 | 18.5 | 21535 | 2025-04-21 23:04:32 | MASTER-Kislovodsk | (16h 05m 49.55s , +29d 59m 23.6s) | C | 60 | 18.3 | 21618 | 2025-04-21 23:05:55 | MASTER-Kislovodsk | (16h 00m 56.86s , +28d 56m 50.7s) | C | 60 | 18.5 | 21701 | 2025-04-21 23:07:19 | MASTER-Kislovodsk | (15h 57m 26.75s , +26d 09m 30.2s) | C | 60 | 18.5 | 21784 | 2025-04-21 23:08:42 | MASTER-Kislovodsk | (16h 06m 15.13s , +26d 08m 27.7s) | C | 60 | 18.3 | 21872 | 2025-04-21 23:10:10 | MASTER-Kislovodsk | (15h 57m 30.28s , +27d 55m 28.7s) | C | 60 | 18.4 | 21962 | 2025-04-21 23:11:40 | MASTER-Kislovodsk | (16h 05m 31.54s , +28d 05m 04.3s) | C | 60 | 18.5 | 22051 | 2025-04-21 23:13:08 | MASTER-Kislovodsk | (15h 57m 31.03s , +29d 48m 52.4s) | C | 60 | 18.4 | 22134 | 2025-04-21 23:14:31 | MASTER-Kislovodsk | (16h 03m 33.66s , +28d 48m 15.9s) | C | 60 | 18.2 | 22225 | 2025-04-21 23:16:02 | MASTER-Kislovodsk | (16h 05m 42.85s , +29d 58m 37.8s) | C | 60 | 18.5 | 22313 | 2025-04-21 23:17:31 | MASTER-Kislovodsk | (15h 58m 22.90s , +26d 02m 50.4s) | C | 60 | 18.5 | 22396 | 2025-04-21 23:18:53 | MASTER-Kislovodsk | (16h 07m 20.08s , +26d 01m 46.7s) | C | 60 | 18.4 | 22480 | 2025-04-21 23:20:17 | MASTER-Kislovodsk | (15h 57m 23.52s , +27d 54m 39.6s) | C | 60 | 18.3 | 22561 | 2025-04-21 23:21:39 | MASTER-Kislovodsk | (16h 06m 31.84s , +27d 54m 51.5s) | C | 60 | 18.4 | 22645 | 2025-04-21 23:23:02 | MASTER-Kislovodsk | (16h 03m 47.65s , +28d 48m 03.3s) | C | 60 | 18.4 | 22729 | 2025-04-21 23:24:27 | MASTER-Kislovodsk | (15h 57m 30.40s , +29d 47m 32.2s) | C | 60 | 18.5 | 22821 | 2025-04-21 23:25:59 | MASTER-Kislovodsk | (16h 06m 46.00s , +29d 49m 01.6s) | C | 60 | 18.3 | 22905 | 2025-04-21 23:27:23 | MASTER-Kislovodsk | (16h 02m 59.34s , +28d 47m 13.7s) | C | 60 | 18.4 | 22989 | 2025-04-21 23:28:46 | MASTER-Kislovodsk | (15h 58m 20.68s , +26d 01m 13.8s) | C | 60 | 18.4 | 23079 | 2025-04-21 23:30:17 | MASTER-Kislovodsk | (16h 07m 19.99s , +26d 00m 16.2s) | C | 60 | 18.4 | 23168 | 2025-04-21 23:31:46 | MASTER-Kislovodsk | (15h 57m 22.17s , +27d 53m 08.2s) | C | 60 | 18.2 | 23249 | 2025-04-21 23:33:07 | MASTER-Kislovodsk | (16h 06m 30.59s , +27d 53m 33.5s) | C | 60 | 18.4 | 23332 | 2025-04-21 23:34:30 | MASTER-Kislovodsk | (15h 57m 29.74s , +29d 49m 01.8s) | C | 60 | 18.3 | 23416 | 2025-04-21 23:35:53 | MASTER-Kislovodsk | (16h 02m 59.31s , +28d 46m 20.5s) | C | 60 | 18.4 | 23500 | 2025-04-21 23:37:17 | MASTER-Kislovodsk | (16h 06m 46.26s , +29d 48m 42.9s) | C | 60 | 18.5 | 23582 | 2025-04-21 23:38:40 | MASTER-Kislovodsk | (15h 58m 38.21s , +31d 42m 59.5s) | C | 60 | 18.3 | 23675 | 2025-04-21 23:40:13 | MASTER-Kislovodsk | (16h 08m 06.89s , +31d 42m 00.6s) | C | 60 | 18.3 | 23758 | 2025-04-21 23:41:36 | MASTER-Kislovodsk | (15h 58m 20.02s , +25d 59m 10.7s) | C | 60 | 18.3 | 23841 | 2025-04-21 23:42:59 | MASTER-Kislovodsk | (16h 07m 19.25s , +25d 59m 29.4s) | C | 60 | 18.3 | 23923 | 2025-04-21 23:44:21 | MASTER-Kislovodsk | (15h 57m 24.42s , +27d 55m 01.1s) | C | 60 | 18.4 | 24006 | 2025-04-21 23:45:44 | MASTER-Kislovodsk | (16h 06m 29.06s , +27d 53m 16.7s) | C | 60 | 18.4 | 24089 | 2025-04-21 23:47:06 | MASTER-Kislovodsk | (15h 57m 31.86s , +29d 48m 38.3s) | C | 60 | 18.4 | 24171 | 2025-04-21 23:48:29 | MASTER-Kislovodsk | (16h 06m 39.44s , +29d 48m 02.0s) | C | 60 | 18.5 | 24253 | 2025-04-21 23:49:51 | MASTER-Kislovodsk | (15h 58m 34.34s , +31d 42m 56.4s) | C | 60 | 18.3 | 24337 | 2025-04-21 23:51:15 | MASTER-Kislovodsk | (16h 08m 07.18s , +31d 42m 00.6s) | C | 60 | 18.2 | 24419 | 2025-04-21 23:52:37 | MASTER-Kislovodsk | (15h 58m 19.75s , +25d 59m 08.0s) | C | 60 | 18.5 | 24503 | 2025-04-21 23:54:00 | MASTER-Kislovodsk | (16h 07m 17.89s , +25d 59m 14.5s) | C | 60 | 18.3 | 24586 | 2025-04-21 23:55:24 | MASTER-Kislovodsk | (15h 57m 24.98s , +27d 54m 39.2s) | C | 60 | 18.4 | 24671 | 2025-04-21 23:56:48 | MASTER-Kislovodsk | (16h 06m 27.62s , +27d 53m 20.7s) | C | 60 | 18.4 | 24754 | 2025-04-21 23:58:11 | MASTER-Kislovodsk | (15h 57m 31.26s , +29d 48m 28.6s) | C | 60 | 18.5 | 24836 | 2025-04-21 23:59:34 | MASTER-Kislovodsk | (16h 06m 39.93s , +29d 48m 02.0s) | C | 60 | 18.1 | 24918 | 2025-04-22 00:00:56 | MASTER-Kislovodsk | (15h 58m 34.74s , +31d 42m 54.9s) | C | 60 | 18.3 | 25011 | 2025-04-22 00:02:29 | MASTER-Kislovodsk | (16h 08m 04.50s , +31d 41m 58.9s) | C | 60 | 18.3 | 25095 | 2025-04-22 00:03:52 | MASTER-Kislovodsk | (15h 58m 19.27s , +25d 59m 06.6s) | C | 60 | 18.5 | 25178 | 2025-04-22 00:05:15 | MASTER-Kislovodsk | (16h 07m 18.60s , +25d 59m 18.3s) | C | 60 | 18.4 | 25260 | 2025-04-22 00:06:37 | MASTER-Kislovodsk | (16h 14m 35.48s , +27d 53m 24.2s) | C | 60 | 18.4 | 25423 | 2025-04-22 00:09:20 | MASTER-Kislovodsk | (16h 14m 55.83s , +29d 49m 02.3s) | C | 60 | 18.5 | 25591 | 2025-04-22 00:12:08 | MASTER-Kislovodsk | (15h 58m 33.07s , +31d 40m 48.1s) | C | 60 | 18.4 | 25673 | 2025-04-22 00:13:31 | MASTER-Kislovodsk | (16h 08m 05.94s , +31d 41m 04.6s) | C | 60 | 18.4 | 25838 | 2025-04-22 00:16:16 | MASTER-Kislovodsk | (15h 49m 17.53s , +27d 54m 38.2s) | C | 60 | 18.3 | 25922 | 2025-04-22 00:17:39 | MASTER-Kislovodsk | (16h 14m 33.10s , +27d 54m 04.7s) | C | 60 | 18.4 | 26099 | 2025-04-22 00:20:37 | MASTER-Kislovodsk | (16h 15m 02.20s , +29d 47m 57.2s) | C | 60 | 18.0 | 26268 | 2025-04-22 00:23:25 | MASTER-Kislovodsk | (15h 58m 40.47s , +31d 41m 07.7s) | C | 60 | 18.4 | 26350 | 2025-04-22 00:24:47 | MASTER-Kislovodsk | (16h 08m 00.84s , +31d 42m 25.0s) | C | 60 | 18.4 | 26517 | 2025-04-22 00:27:34 | MASTER-Kislovodsk | (15h 49m 16.89s , +27d 54m 28.4s) | C | 60 | 18.3 | 26600 | 2025-04-22 00:28:57 | MASTER-Kislovodsk | (16h 14m 31.40s , +27d 53m 55.4s) | C | 60 | 18.5 | Filter C is a clear (unfiltred) band.

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

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