{
  "bibcode": "2015GCN.18511....1B",
  "body": "D.Buckley, S. Potter, A.Kniazev, M.Kotze\nSouth African Astronomical Observatory\n\nR. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres\nThe Instituto de Astrofisica de Canarias\n\nE. Gorbovskoy, V. Lipunov,    N.Tyurina, V.Kornilov, \nP.Balanutsa, A.Kuznetsov, D.Kuvshinov, D. Vlasenko, E.Popova\nLomonosov Moscow State University, Sternberg Astronomical Institute\n\nK.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk\nIrkutsk State University\n\nA. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik\nKislovodsk Solar Station of the Pulkovo Observatory\n\nV.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov\nBlagoveschensk Educational State University, Blagoveschensk\n\nV.Krushinski, I.Zalozhnih\nUral Federal University, Kourovka\n\nHugo Levato and Carlos Saffe\nInstituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)\n\nClaudio Mallamaci, Carlos Lopez and Federico Podest\nObservatorio Astronomico Felix Aguilar (OAFA)\n\n\nTwo MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) \nlocated in SAAO and IAC was pointed to the  GRB151027B (Ukwatta et. al GCN \n18499) 25 sec after notice time and 156 sec after trigger time at \n2015-10-27 22:43:19 UT. On our first (30s exposure)  set we haven`t found \noptical transient (Malesani et. al. GCN 18501, Xu et. al. GCN 18505, \nWiseman et. al GCN 18507)  within SWIFT error-box. The 2-sigma upper limit \nhas been about 17.7 mag. The observations were significantly complicate \nthe closest distance to the Moon (~ 35 d). The Moon background light is \npicked up the sky background on our cameras more than 10 times. Therefore, \nwe could not get deep enough image. Nevertheless, we detect OT on a \nseveral coadd images in consequent time  in  SAAO.\nThe first time we see  OT 475 seconds after the trigger with magnitude ~ \n18.9.  OT had a slight brightening 1736 seconds after the trigger to 18.5 \nmag.\nThe preliminary photometry available at table below.\n\nTable 1. GRB151027B MASTER-SAAO Early photometry.\n\nT-Ts    T-Tm     Exptime   Mag.(P/+P\\)   Coadd\n159      174     2 x 30     >17.7          1\n201      221     2 x 40     >18.0          1\n252      277     2 x 50     >18.3          1\n313      343     2 x 60     >18.3          1\n384      424     2 x 80     >18.4          1\n159      311     2 x 260    >19.0          5\n475      842     2 x 690     18.9          5\n1235    1736     2 x 900     18.5          5\n2264    3280    2 x 1800     18.9         10\n3499    4515    2 x 1800     19.1         10\n\nT - is trigger time, Ts - exposure start time, Tm - exposure middle time.\n\n\nWe see OT in separate polarizations on s/n~5 confidence lewel. Table 1 \nshows the averaged data from two mutually perpendicular polarization.\n\n\nThe message may be cited.",
  "circularId": 18511,
  "createdOn": 1446038679000,
  "email": "lipunov@xray.sai.msu.ru",
  "subject": "GRB 151027B: MASTER-NET early OT detection",
  "submitter": "Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>",
  "eventId": "GRB 151027B"
}