Gamma rays from dark mediators in white dwarfs

TL;DR

This paper investigates gamma-ray signals from dark matter annihilation into metastable mediators inside white dwarfs, considering mediator decay and energy loss effects, and derives constraints on mediator lifetimes using astrophysical data.

Contribution

It introduces a detailed model of dark matter annihilation into mediators within white dwarfs, including mediator energy loss and decay, and constrains mediator lifetimes with astrophysical observations.

Findings

Attenuated gamma-ray luminosities depend on mediator decay and energy loss.

Constraints on mediator lifetimes are derived from white dwarf observations.

The model links dark matter properties with observable gamma-ray signals.

Abstract

We consider self-annihilation of dark matter, $\chi$, into metastable mediators, $Y$, and their subsequent decay into photons inside white dwarfs. We focus on reactions of the type $\chi \bar{\chi}\rightarrow YY$, where mediators, besides having a finite decay lifetime at rest $\tau_{\rm rest}\lesssim 1$ s, may suffer energy loss in the medium before they decay into photons, $Y \rightarrow \gamma\gamma$. We obtain attenuated gamma-ray luminosities arising from the combination of both effects. Using complementary sets of astrophysical measurements from cold white dwarfs in the M4 globular cluster as well as direct/indirect dark matter searches we discuss further constraints on dark mediator lifetimes.