Massive scalar counterpart of gravitational waves in scalarized neutron star binaries

TL;DR

This paper explores the massive scalar gravitational wave counterparts in scalarized neutron star binaries within scalar-tensor theory, revealing their properties and potential observational signatures.

Contribution

It demonstrates that scalarized neutron star binaries produce massive scalar gravitational wave counterparts, with detailed analysis of their origin, mass, and oscillation behavior.

Findings

Massive scalar gravitational wave counterparts are produced in scalarized neutron star binaries.

The scalar field mass can be of the order of the Planck scale or about 10^{-21} eV/c^2.

Scalarized binaries exhibit unique oscillation and radiation characteristics.

Abstract

In analogy with spontaneous magnetization of ferromagnets below the Curie temperature, a neutron star (NS), with a compactness above a certain critical value, may undergo spontaneous scalarization and exhibit an interior nontrivial scalar configuration. Consequently, the exterior space-time is changed, and an external scalar field appears, which subsequently triggers a scalarization of its companion. The dynamical interplay produces a gravitational scalar counterpart of tensor gravitational waves. In this paper, we resort to scalar-tensor theory and demonstrate that the gravitational scalar counterpart from double neutron star (DNS) and neutron star-white dwarf (NS-WD) become massive. We report that (i) a gravitational scalar background field, arising from convergence of external scalar fields, plays the role of gravitational scalar counterpart in scalarized DNS binary, and the appearance of a mass-dimensional constant in Higgs-like gravitational scalar potential is responsible for a massive gravitational scalar counterpart with mass of order of Planck scale; (ii) a dipolar gravitational scalar radiated field, resulting from different binding energy of NS and WD, plays the role of gravitational scalar counterpart in scalarized orbital shrinking NS-WDs, which oscillates around a local and scalar-energy-density dependent minimum of the gravitational scalar potential and gains a mass of the order of about $10^{-21} ev/c^2$.