Self-Interacting Dark Matter in Brown Dwarfs

TL;DR

This paper models how dark matter accumulation in brown dwarfs affects their structure and dynamics, proposing that these effects could help detect dark matter properties through astronomical observations.

Contribution

It introduces a self-consistent two-fluid model for brown dwarfs with dark matter, analyzing how dark matter alters their internal structure and observable characteristics.

Findings

Dark matter accumulation modifies brown dwarf radius and density profile.

Dark matter presence affects the second-order Love number of brown dwarfs.

Structural signatures of dark matter could be detected by future astrometric missions.

Abstract

Brown dwarfs, being transitional objects between giant planets and low-mass stars, possess dense, cool interiors that provide optimal conditions to explore non-standard physics. Capture and accumulation of dark-matter particles can alter the thermal, structural and dynamic of these substellar objects. We aim to apply a self-consistent two-fluid framework to model the internal structure of self-gravitating brown dwarfs and to quantify how the presence of a dark-matter component modifies their mass--radius relations and dynamical properties. The brown dwarf is modeled as a composite system of a baryonic fluid, described by a polytropic equation of state, and an independent dark-matter fluid. Both components are coupled through their shared gravitational potential in hydrostatic equilibrium. We solve numerically the coupled Lane-Emden equations for a range of dark-matter mass fractions. We find that dark matter accumulating in the core reshapes the baryonic density profile, modifying both the radius and the second-order Love number. Radius and dynamical anomalies in brown dwarfs can serve as diagnostic tools to constrain dark-matter properties. Future high-precision astrometric missions could identify these structural signatures, establishing brown dwarfs as possible detectors of dark matter in the Galaxy.