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General Relativity and Quantum Cosmology, gr-qc,High Energy Physics - Phenomenology, hep-ph
Abstract:
We study quasi-equilibrium sequences of binary neutron stars in the framework
of Damour-Esposito-Farese-type scalar-tensor theory of gravity with a massive
scalar field, paying particular attention to the case where neutron stars are
already spontaneously scalarized at distant orbits, i.e., in the high coupling
constant case. Although scalar effects are largely quenched when the separation
$a$ is $\gtrsim 3$--$6$ times of the Compton length-scale that is defined by
the scalar mass, we show that the interaction between the scalar fields of the
two neutron stars generates a scalar cloud surrounding the binary at the price
of orbital energy when $a \lesssim 3$--$6$ times of the Compton length-scale.
This enables us to constrain the scalar mass $m_\phi$ from gravitational-wave
observations of binary neutron star mergers by inspecting the dephasing due to
such phenomenon. In particular, the event GW170817 is suggestive of a
constraint of $m_\phi \gtrsim 10^{-11}$ eV and the coupling strength should be
mild if the neutron stars in this system were spontaneously scalarized.
