Fundamental oscillations as a tool to distinguish boson stars from neutron stars and black holes

TL;DR

This paper demonstrates that the fundamental oscillation modes of boson stars follow a universal scaling law, enabling their distinction from neutron stars and black holes via gravitational wave observations.

Contribution

It introduces the first scaling relations for non-radial fundamental modes of boson stars within full general relativity, facilitating their identification across a wide mass range.

Findings

$f$-mode frequencies are lower than black hole quasinormal modes by a factor of 4.5.

Scaling relations allow mode property predictions for arbitrary boson star masses.

Distinct gravitational wave signatures can differentiate boson stars from other compact objects.

Abstract

Massive boson stars are self-gravitating configurations of self-interacting scalar fields and can be modeled by a massive scalar field with a quartic self-interaction potential. It has been shown that the equation of state and static structure properties, such as mass and radius, follow scaling relations independent of microscopic dark matter properties. In this work, we demonstrate for the first time that non-radial fundamental ($f$-)mode characteristics also follow a scaling in the strong interaction limit, opening up the outstanding prospect of evaluating the mode properties for boson stars for arbitrary masses spanning the scalar dark matter parameter space allowed by current observations. We provide the scaling relations within full general relativity and obtain the mode characteristics corresponding to the maximum boson star mass configuration. We apply these to determine the $f$-mode properties for boson stars solely as a function of their mass and compactness, which allows distinguishing them from those of neutron stars and black hole quasinormal modes in comparable mass range. In particular, we show that the frequencies are always lower than those of corresponding black holes of the same mass by a factor of 4.5. This provides a smoking gun for the distinguishability of boson stars from other compact objects using gravitational wave observations.