Speaker
Mr
Shotaro Yamasaki
(University of Tokyo)
Description
Most fast radio bursts (FRB) do not show evidence of repetition, and such non-repeating
FRBs may be produced at the time of a merger of binary neutron stars (BNS), provided
that the BNS merger rate is close to the high end of the currently possible range. However,
the merger environment is polluted by dynamical ejecta, which may prohibit the
radio signal from propagating.We examine this by using a general-relativistic simulation
of a BNS merger, and show that the ejecta appears about 1ms after the rotation speed
of the merged star becomes the maximum. Therefore there is a time window in which
an FRB signal can reach outside, and the short duration of non-repeating FRBs can be
explained by screening after ejecta formation. A fraction of BNS mergers may leave a
rapidly rotating and stable neutron star, and such objects may be the origin of repeating
FRBs like FRB 121102. We show that a merger remnant would appear as a repeating FRB
on a time scale of 1–10 yr, and expected properties are consistent with the observations
of FRB 121102. We construct an FRB rate evolution model that includes these two
populations of repeating and non-repeating FRBs from BNS mergers, and show that the
detection rate of repeating FRBs relative to non-repeating ones rapidly increases with
improving search sensitivity. This may explain why only the repeating FRB 121102 was
discovered by the most sensitive FRB search with Arecibo. Several predictions are made,
including the appearance of a repeating FRB 1–10 yr after a BNS merger that is localized
by gravitational waves and subsequent electromagnetic radiation.
Primary author
Mr
Shotaro Yamasaki
(University of Tokyo)
Co-authors
Prof.
Kenta Kiuchi
(Kyoto university)
Prof.
Tomonori Totani
(University of Tokyo)
