# Stellar probes of dark sector-photon interactions

## TL;DR

This paper derives constraints on dark sector particles interacting with photons via higher-dimensional operators, using stellar energy loss data from the Sun, horizontal branch stars, red giants, and SN1987A, providing a comprehensive viability overview.

## Contribution

It offers the first detailed calculation of stellar energy loss constraints on electromagnetic dark-state interactions across a wide mass range, including resonance effects and in-medium processes.

## Key findings

- Stringent limits for dark states below 3 keV and 40 MeV from red giants and SN1987A.
- Effective lower mass-scale constraints of 10^9 GeV and 10^7 GeV for mass-dimension five operators.
- First comprehensive overview of electromagnetic dark-state interactions below the GeV scale.

## Abstract

Electromagnetically neutral dark sector particles may directly couple to the photon through higher dimensional effective operators. Considering electric and magnetic dipole moment, anapole moment, and charge radius interactions, we derive constraints from stellar energy loss in the Sun, horizontal branch and red giant stars, as well as from cooling of the proto-neutron star of SN1987A. We provide the exact formula for in-medium photon-mediated pair production to leading order in the dark coupling, and compute the energy loss rates explicitly for the most important processes, including a careful discussion on resonances and potential double counting between the processes. Stringent limits for dark states with masses below $3\,$keV ($40\,$MeV) arise from red giant stars (SN1987A), implying an effective lower mass-scale of approximately $10^9\,$GeV ($10^7\,$GeV) for mass-dimension five, and $100\,$GeV ($2.5\,$TeV) for mass-dimension six operators as long as dark states stream freely; for the proto-neutron star, the trapping of dark states is also evaluated. Together with direct limits previously derived by us in Chu et al. (2018), this provides the first comprehensive overview of the viability of effective electromagnetic dark-state interactions below the GeV mass-scale.