GRB 160625B: Mini-MegaTORTORA detection of bright optical flash simultaneous with LAT event
The on-sky position of GRB 160625B (Dirirsa et al., GCN Circ. 19580)
has been observed by Mini-MegaTORTORA
nine-channel wide-field monitoring system with high temporal
resolution before, during and just after the LAT trigger
time (T0 = 2016-06-25 22:43:24).
Mini-MegaTORTORA reacted to Fermi GBM trigger 488587220 and started
observing its error box at 2016-06-25 22:41:07, 52 seconds after GBM
trigger and 136 seconds before LAT trigger. Due to large
size of error box, the observations have been performed in "widefield+deep"
regime, with channels simultaneously covering ~30x30 deg field of view
with 30 s exposures in white light to achieve deepest
detection limit. The system acquired 20 frames in such regime, covering
time interval from T0-136 to T0+466 s.
Fig.1. First 20 images of the 20' x 20' region of the GRB160625B gamma-ray burst obtained with the Mini-MegaTORTORA system (a green circle indicates the position of the optical flare)
Fig.2. Light curve of the optical flare coinciding in time with the GRB160625B gamma-ray burst from observations in white light of the Mini-MegaTORTORA system (brightness measurements are given in the visible band)