{
  "bibcode": "2017GCN.22030....1K",
  "body": "S.Karpov, G.Beskin (SAO RAS and Kazan Federal University, Russia), S.Bondar,\nE.Ivanov, E.Katkova, N.Orekhova, A.Perkov (OJS RPC PSI, Russia), A.Biryukov\n(SAI MSU and Kazan Federal University, Russia), V.Sasyuk (Kazan Federal\nUniversity, Russia)\n\nMini-MegaTORTORA nine-channel wide-field monitoring system with high\ntemporal resolution has been observing the Swift field of view before,\nduring and after the time of Swift BAT trigger corresponding to GRB171020A\n(Page et al, GCN 22028). The whole burst localization region has been\ncovered since 2017-10-20 23:00:07.90 UT (T0-422 s) and until 2017-10-20\n23:10:17.68 UT (T0+187 s, thus including the whole gamma-ray activity\ninterval) with temporal resolution of 0.1 s in white light. Dedicated\nreal-time transient detection pipeline did not detect any events longer\nthan 0.3 s and brighter than approximately V=10.5 mag during this interval.\nVisual inspection of co-added images with 10 s effective exposure\n(summation of 100 consecutive frames each) has not revealed any variable\nsource down to V=12.0 mag during that interval. Also, the multi-regime\nfollow-up (when all channels except for the one containing the trigger are\nrepointed towards it and observe it with various exposures with and without\nphotometric and polarimetric filters installed) has been initiated at\n2017-10-20 23:08:12.0 UT (T0+61.25 s). The inspection of 10 s exposure\nframes acquired in white light between 2017-10-20 23:08:12.0 UT (T0+61.25\ns) and 2017-10-20 23:09:43 UT (T0+152.25 s) did not reveal any source\nbrighter than V=13.5 mag at the position of the burst.\n\nMini-MegaTORTORA belongs to Kazan Federal University and is located at\nSpecial Astrophysical Observatory near Russian 6-m telescope.\n\nThe message may be cited.",
  "circularId": 22030,
  "createdOn": 1508545877000,
  "email": "karpov@sao.ru",
  "subject": "GRB 171020A: Mini-MegaTORTORA upper limits on simultaneous optical emission",
  "submitter": "Sergey Karpov at SAO RAS  <karpov@sao.ru>",
  "eventId": "GRB 171020A"
}