(Proposal ID) S17B-116

(PI) Tanaka, Yasuyuki

(Proposal Title)
Subaru follow-up for IceCube neutrino event

(Abstract)
The IceCube South Pole Neutrino Observatory has reported the first detection 
of TeV-PeV astrophysical neutrino events. Although a total of 54 astrophysical 
neutrino events were detected from the 4-year IceCube data, the origin is still
unclear. To unveil the neutrino source, it is essential to discover the 
electromagnetic (EM) counterpart and study the astrophysical properties 
through prompt follow-up observation. Since 2016 April the IceCube team has 
started to issue a neutrino detection alert. Here we propose Subaru ToO 
observation toward the IceCube neutrino error region, once we receive the 
IceCube alert. Since the 90% containment radius of the IceCube event is <0.8 
deg, the wide field-of-view of HSC (1.5 deg diameter) perfectly matches the 
optical counterpart search. In theoretical viewpoint, the most plausible 
neutrino source is considered to be a flaring blazar. Hence by assuming this 
scenario we select flat-spectrum radio sources using radio catalogs and among 
them we identify a brightening source showing large-amplitude and rapidly-
variable light curve as an IceCube counterpart. To do this, we request 2 epochs
of 0.5 night exposure.