Models of rotating boson stars and geodesics around them: new type of orbits

TL;DR

This paper develops a numerical code to construct rotating boson stars in general relativity, explores their properties including maximum mass and unique geodesic orbits, and identifies new orbit types that could distinguish these objects from black holes.

Contribution

The study presents the first numerical solutions for rotating boson stars with higher rotational quantum numbers and investigates their geodesic structure, revealing novel orbit types.

Findings

First solutions for rotating boson stars with k=3 and 4.

Determination of maximum mass for k=2 boson stars.

Identification of zero-angular-momentum orbits near boson stars.

Abstract

We have developed a highly accurate numerical code capable of solving the coupled Einstein-Klein-Gordon system, in order to construct rotating boson stars in general relativity. Free fields and self-interacting fields, with quartic and sextic potentials, are considered. In particular, we present the first numerical solutions of rotating boson stars with rotational quantum number $k=3$ and $k=4$, as well as the first determination of the maximum mass of free-field boson stars with $k=2$. We have also investigated timelike geodesics in the spacetime generated by a rotating boson star for $k=1$, $2$ and $3$. A numerical integration of the geodesic equation has enabled us to identify a peculiar type of orbits: the zero-angular-momentum ones. These orbits pass very close to the center and are qualitatively different from orbits around a Kerr black hole. Should such orbits be observed, they would put stringent constraints on astrophysical compact objects like the Galactic center.