Gravitational-Wave Asteroseismology with Fundamental Modes from Compact Binary Inspirals. (arXiv:1905.00817v1 [gr-qc])
<a href="http://arxiv.org/find/gr-qc/1/au:+Pratten_G/0/1/0/all/0/1">Geraint Pratten</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Schmidt_P/0/1/0/all/0/1">Patricia Schmidt</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Hinderer_T/0/1/0/all/0/1">Tanja Hinderer</a>
The first detection of gravitational waves (GWs) from the binary neutron star
(NS) inspiral GW170817 has opened a unique channel for probing the fundamental
properties of matter at supra-nuclear densities inaccessible elsewhere in the
Universe. This observation yielded the first constraints on the equation of
state (EoS) of NS matter from the GW imprint of tidal interactions. Tidal
signatures in the GW arise from the response of a matter object to the
spacetime curvature sourced by its binary companion. They crucially depend on
the EoS and are predominantly characterised by the tidal deformability
parameters $Lambda_{ell}$, where $ell=2,3$ denotes the quadrupole and
octupole respectively. As the binary evolves towards merger, additional
dynamical tidal effects become important when the orbital frequency approaches
a resonance with the stars’ internal oscillation modes. Among these modes, the
fundamental ($f_ell$-)modes have the strongest tidal coupling and can give
rise to a cumulative imprint in the GW signal even if the resonance is not
fully excited. Here we present the first direct constraints on fundamental
oscillation mode frequencies for GW170817 using an inspiral GW phase model with
an explicit dependence on the $f$-mode frequency and without assuming any
relation between $f_ell$ and $Lambda_ell$. We rule out anomalously small
values of $f_ell$ and, for the larger companion, determine a lower bound on
the $f_2$-mode ($f_3$-mode) frequency of $geq 1.39$ kHz ($geq 1.86$ kHz) at
the 90% credible interval (CI). We then show that networks of future GW
detectors will be able to measure $f$-mode frequencies to within tens of Hz
from the inspiral alone. Such precision astroseismology will enable novel tests
of fundamental physics and the nature of compact binaries.
The first detection of gravitational waves (GWs) from the binary neutron star
(NS) inspiral GW170817 has opened a unique channel for probing the fundamental
properties of matter at supra-nuclear densities inaccessible elsewhere in the
Universe. This observation yielded the first constraints on the equation of
state (EoS) of NS matter from the GW imprint of tidal interactions. Tidal
signatures in the GW arise from the response of a matter object to the
spacetime curvature sourced by its binary companion. They crucially depend on
the EoS and are predominantly characterised by the tidal deformability
parameters $Lambda_{ell}$, where $ell=2,3$ denotes the quadrupole and
octupole respectively. As the binary evolves towards merger, additional
dynamical tidal effects become important when the orbital frequency approaches
a resonance with the stars’ internal oscillation modes. Among these modes, the
fundamental ($f_ell$-)modes have the strongest tidal coupling and can give
rise to a cumulative imprint in the GW signal even if the resonance is not
fully excited. Here we present the first direct constraints on fundamental
oscillation mode frequencies for GW170817 using an inspiral GW phase model with
an explicit dependence on the $f$-mode frequency and without assuming any
relation between $f_ell$ and $Lambda_ell$. We rule out anomalously small
values of $f_ell$ and, for the larger companion, determine a lower bound on
the $f_2$-mode ($f_3$-mode) frequency of $geq 1.39$ kHz ($geq 1.86$ kHz) at
the 90% credible interval (CI). We then show that networks of future GW
detectors will be able to measure $f$-mode frequencies to within tens of Hz
from the inspiral alone. Such precision astroseismology will enable novel tests
of fundamental physics and the nature of compact binaries.
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