Modified gravity in the interior of population II stars

We study the effects of a beyond-Horndeski theory of modified gravity in the interior of a population II star. We consider a simple phenomenological model of a 1.1M(circle dot) star that has left the main sequence, has a thin Hydrogen burning shell with a partially degenerate isothermal core, surrounded by a radiative envelope having two regions of distinct opacities. Using suitable matching conditions at the two internal boundaries, a numerical analysis of the resulting stellar equations in modified gravity is carried out. While overall, gravity may be weakened, resulting in a decrease of the luminosity and an increase of the radius of the star, some of these effects are reversed near the core. It is suggested how the model, within its limitations, can yield a bound on the modified gravity parameter.

Automated summary

The study investigates the effects of modified gravity beyond Horndeski theory in the interior of a population II star, finding that reduced gravity may result in decreased luminosity and increased radius of the star, but some effects are reversed near the core. The model provides a constraint on the modified gravity parameter within its limitations.