[vsnet-grb-info 17213] GRB 151107B: Mini-MegaTORTORA limits on simultaneous optical emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18574
SUBJECT: GRB 151107B: Mini-MegaTORTORA limits on simultaneous optical emission
DATE:    15/11/10 17:29:27 GMT
FROM:    Sergey Karpov at SAO RAS  <karpov at sao.ru>

S.Karpov, G.Beskin (SAO RAS and Kazan Federal University, Russia), S.Bondar,
E.Ivanov, E.Katkova, A.Perkov, N.Orekhova (OJS RPC PSI, Russia), A.Biryukov
(SAI MSU and Kazan Federal University, Russia), V.Sasyuk (Kazan Federal
University, Russia)

The localization of Fermi GBM trigger 468620696 / GRB 151107B (Stanbro et al,
GCN Circ. 18570) has been observed by Mini-MegaTORTORA nine-channel wide-field
monitoring system (located at Special Astrophysical Observatory near Russian
6-m telescope and belonging to Kazan Federal University) before, during and
after the trigger time at 2015-11-07 20:24:52.30 UT. The whole final 1-sigma
localization box (as well as 6 more degrees around it) has been covered since
20:19:23 UT (T-329.3 s) and until 20:25:18 UT (T+25.7 s, thus covering the
brightest part of first gamma-ray peak) with temporal resolution of 0.1 s in
white light. Dedicated real-time transient detection pipeline did not detect
any events longer than 0.3 s and brighter than approximately V=10.5 mag. Visual
inspection of co-added images with 10 s effective exposure (summation of 100
consecutive frames each) has not revealed any variable source down to V=12.0
mag during that interval.

At 20:25:18 UT the system initiated a repointing following the initially
distributed GBM coordinates, and since 20:25:55 UT (T+62.7 s, during the
continuing gamma-ray activity) till 20:35:59 UT (T+666.7 s) acquired 20x9 deep
images with 30 s exposures in white light in a 30x30 degree field of view
centered on RA=24.1 Dec=44.8. The whole final 1-sigma localization was still
inside the field of view. Quick-look analysis of the acquired data has not
revealed any variable object down to roughly V=13.5 mag over that time interval.

The analysis is ongoing.