{
  "bibcode": "2021GCN.30747....1L",
  "body": "V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, \nV.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,\nD.Kuvshinov,  D. Cheryasov\n(Lomonosov Moscow State University, SAI, Physics Department),\n\nR. Podesta, C.Lopez, F. Podesta, C.Francile \n(Observatorio Astronomico Felix Aguilar OAFA),\n\nR. Rebolo, M. Serra \n(The Instituto de Astrofisica de Canarias),\n\nD. Buckley \n(South African Astronomical Observatory),\n\nO.A. Gres, N.M. Budnev, O.Ershova \n(Irkutsk State University, API),\n\nA. Tlatov, D. Dormidontov \n(Kislovodsk Solar Station of the Pulkovo Observatory),\n\nV. Yurkov, A. Gabovich, Yu. Sergienko \n(Blagoveschensk Educational State University)\n\n\n\n\nMASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 210901A ( S. Laha et al., GCN 30746) errorbox  6860 sec after notice time and 6950 sec after trigger time at 2021-09-01 17:00:26 UT, with upper limit up to  18.6 mag. Observations started at twilight.  The observations began at zenith distance = 49 deg. The sun  altitude  is -8.9 deg. \n\nThe galactic latitude b = -30 deg., longitude l = 318 deg.\n\n\nReal time updated cover map and OT discovered available here: \nhttps://master.sai.msu.ru/site/master2/observ.php?id=1706835\n\nWe obtain a following upper limits.  \n\nTmid-T0  |          Site       |Filt.| Expt. | Limit| Comment\n_________|_____________________|_____|_______|______|________\n\n    7040 |         MASTER-SAAO |   C |   180 | 17.4 |        \n    7220 |         MASTER-SAAO |   C |   540 | 17.8 |  Coadd \n    7240 |         MASTER-SAAO |   C |   180 | 17.9 |        \n    7439 |         MASTER-SAAO |   C |   180 | 18.3 |        \n    7639 |         MASTER-SAAO |   C |   180 | 18.6 |        \nFilter C is a clear (unfiltred) band. \n\n\nThe observation and reduction will continue. \nThe message may be cited.",
  "circularId": 30747,
  "createdOn": 1630517021000,
  "email": "lipunov@xray.sai.msu.ru",
  "subject": "Swift GRB 210901A: Global MASTER-Net observations report",
  "submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>",
  "eventId": "GRB 210901A"
}