Dark Photons from Red Dwarfs

Light dark photons can be produced in stellar systems and thus contribute to the stellar cooling rate. The additional cooling changes the evolution of the star and has an impact on various observable properties such as radius, photon luminosity or the emitted neutrino fluxes. This has been exploited before to derive limits based on observations of the Sun, horizontal branch stars and red giants. Given the wealth of astrophysical data collected in the last decade and the improvements in modeling stellar evolution it is interesting to investigate whether other stellar systems offer a complementary avenue towards testing dark photons. In this work, we study the effect on an alternative class of stars. We focus on the impact of dark photon induced cooling on red dwarfs, i.e. the lowest mass stars on the Hydrogen main sequence. Running simulations of the evolution of red dwarfs with dark photon cooling we determine the impact on the mass-radius relation. Combining our simulations with precise determination of mass and radius derived from observations of eclipsing binaries that have recently become available, we derive competitive limits which outperform the solar ones in a significant part of the parameter space.