Signatures of Mirror Stars

TL;DR

Mirror Stars, hypothetical objects in hidden sectors with SM-like physics, could be detected via faint optical signals from captured matter and distinctive X-ray emissions caused by dark photon conversion, offering a new way to probe dark sectors.

Contribution

This paper introduces the concept of Mirror Stars with observable signatures due to kinetic mixing, providing the first detailed predictions of their optical and X-ray signals.

Findings

Mirror Stars can capture SM matter, producing faint optical signals.

Dark photon to SM photon conversion leads to detectable X-ray emissions.

Potential detection range up to 100-1000 light years for certain parameters.

Abstract

Motivated by theories of Neutral Naturalness, we argue that \emph{Mirror Stars} are a generic possibility in any hidden sector with analogues of Standard Model (SM) electromagnetism and nuclear physics. We show that if there exists a tiny kinetic mixing between the dark photon and the SM photon, Mirror Stars capture SM matter from the interstellar medium, which accumulates in the core of the Mirror Star and radiates in the visible spectrum. This signature is similar to, but in most cases much fainter than, ordinary white dwarfs. We also show for the first time that in the presence of captured SM matter, a fraction of dark photons from the core of the Mirror Star convert directly to SM photons, which leads to an X-ray signal that represents a direct probe of the properties of the Mirror Star core. These two signatures together are a highly distinctive, smoking gun signature of Mirror Stars. We show that Mirror Stars could be discovered in both optical and X-ray searches up to approximately 100-1000 light years away, for a range of well-motivated values of the kinetic mixing parameter.