Boson Stars in Bumblebee Gravity and Their Gravitational Waveforms from Extreme-Mass-Ratio Inspirals

TL;DR

This paper explores how Lorentz violation in bumblebee gravity affects boson star structures and their gravitational wave signals from EMRIs, revealing distinctive, detectable waveform features that could constrain Lorentz-violating theories.

Contribution

It introduces a detailed analysis of boson stars in bumblebee gravity, showing how Lorentz violation alters their structure and gravitational wave signatures, with implications for LISA observations.

Findings

Positive Lorentz violation parameter enhances gravitational binding.

Structural changes affect EMRI orbital dynamics and waveforms.

Detectable gravitational wave signatures within LISA's sensitivity range.

Abstract

We investigate the impact of Lorentz violation on the internal structure of mini-boson stars and the resulting gravitational-wave signals from extreme-mass-ratio inspirals (EMRIs) within the framework of bumblebee gravity. Numerical solutions for static, spherically symmetric configurations reveal that a positive Lorentz-violating parameter $\ell$ suppresses repulsive pressure, thereby enhancing gravitational binding and yielding more compact boson stars. Conversely, a negative $\ell$ amplifies repulsive pressure and weakens gravitational binding, such that no static solutions exist beyond a critical negative value. These structural modifications imprint distinct features on EMRI dynamics, characterized by a monotonic decrease in both orbital eccentricity and radial range as $\ell$ increases. Unlike the intermittent bursts from grazing orbits that resemble black-hole signals, penetrating orbits that enter the boson-star core exhibit sustained, amplitude-modulated gravitational-wave signatures without quiet intervals. Their characteristic strain falls within the detectability range of LISA, providing a potential observable for constraining Lorentz violation.