Gravitational Waves from Accretion-Induced Descalarization in Massive Scalar-Tensor Theory

Area of Science:

• Astrophysics
• Gravitational Physics
• Theoretical Physics

Background:

• Extended scalar-tensor theories predict dynamical instabilities at high energies, forming scalarized neutron stars.
• Scalarized neutron stars can exhibit mass-twin phenomena similar to general relativity, with lower maximum mass and central energy density.
• These stars may exceed critical mass limits, triggering a gravitational phase transition where scalar hair is shed.

Purpose of the Study:

• To dynamically track gravitational transitions in scalarized neutron stars.
• To investigate the characteristics of gravitational wave and electromagnetic signals emitted during these transitions.
• To assess the detectability of these events with current and future gravitational wave observatories.

Main Methods:

• Construction of hydrostatic, scalarized equilibria for realistic equations of state.
• Dynamic simulation of accretion onto scalarized neutron stars beyond their critical mass.
• Analysis of the resulting monopolar radiation bursts and their signal properties.

Main Results:

• Gravitational transitions result in bursts of monopolar radiation, stretched into quasicontinuous signals lasting decades.
• Detectable gravitational wave strains of ~10^-22 (kpc/L)^(3/2) Hz^-1/2 at <300 Hz are predicted.
• Events are detectable out to ~10 kpc with current interferometers and further with the Einstein Telescope.

Conclusions:

• Scalarized neutron stars offer a unique probe of modified gravity theories through observable gravitational and electromagnetic signatures.
• Gravitational transitions represent a distinct astrophysical phenomenon with potential for multi-messenger astronomy.
• The predicted signals are within the reach of next-generation gravitational wave detectors, enabling observational tests of these theories.