Ultralight bosonic dark matter in white dwarfs and potential observational consequences

TL;DR

This paper investigates how ultralight bosonic dark matter can form stable mixed white dwarf-boson star configurations, affecting observable properties like gravitational redshift, with potential implications for dark matter detection through astrophysical observations.

Contribution

It presents a detailed study of the dynamical formation of mixed white dwarf-boson stars via gravitational cooling, highlighting their properties and observational consequences.

Findings

White dwarfs can develop boson star cores due to dark matter accretion.

The presence of boson star cores alters gravitational redshift measurements.

Dark matter effects could cause discrepancies in white dwarf mass and radius estimates.

Abstract

Fluid and ultralight bosonic dark matter can interact through gravity to form stable fermion-boson stars, which are static and regular mixed solutions of the Einstein-Euler-(complex, massive) Klein-Gordon system. In this work we study the dynamical formation via gravitational cooling of a spherical mixed white-dwarf--boson star, whose properties depend on the boson particle mass and the mass of the boson star. Due to the accretion of bosonic dark matter, the white dwarf migrates to a denser and more compact object with a boson star core, thus modifying its gravitational redshift and altering the electromagnetic radiation emitted from the photosphere. We discuss the implications of the changes in the gravitational redshift that in principle could be produced by any type of dark matter and that might lead to small discrepancies in the estimation of masses and radii derived from white dwarf observations.