Speaker
Brian Metzger
Description
Hopes are high that Advanced LIGO/Virgo will detect
coalescing binary neutron stars
in the next few years. Maximizing the scientific return
from this discovery will require
identifying a coincident electromagnetic counterpart. One
possible counterpart is a
thermal optical/IR transient, powered by the radioactive
decay of neutron-rich
elements synthesized in the merger ejecta (a `kilonova'). In
addition to providing a
beacon to the gravitational wave chirp, kilonovae provide a
direct probe of an
astrophysical site for rapid neutron capture (r-process)
nucleosynthesis. I will present
the first 3D MHD simulations of the long-term evolution of
the remnant accretion disk
produced in NS-NS/NS-BH mergers. Over ~400 ms of evolution,
we find the ejection
of ~20% of the initial torus mass in powerful neutron-rich
winds, confirming this
important of this site for the r-process in addition to the
dynamical ejecta. I will
describe how the lifetime of the hypermassive neutron star
may impact the kilonova
light curves and color. Free neutrons in the outermost
layers of the ejecta could power
a bright hours long ’precursor' to the main kilonova
emission, greatly enhancing the
prospects for its detection. The small fraction of short
gamma-ray bursts
accompanied by unexpectedly long-lived X-ray emission may
suggest that a fraction of
mergers result in the formation of long-lived - or even
indefinitely stable - massive
neutron star remnants; if confirmed, this would place
stringent constraints on the high
density equation of state.
