Neutron-mirror neutron mixing and neutron stars

Abstract The oscillation of neutron n into mirror $$n'$$ n ′ , its mass degenerate partner from dark sector, can gradually transform the stars mixed consisting in part matter. In quark $$n-n'$$ - transitions are suppressed. We study structure and derive mass-radius scaling relations between configurations purely star maximally (MMS) containing equal amounts ordinary components. particular, we show that MMS masses be at most $$M^{\mathrm{max}}_{NS}/\sqrt{2}$$ M NS max / 2 where $$M^\mathrm{max}_{NS}$$ is a maximum pure allowed by given equation state. evaluate transition rate stars, various astrophysical limits on pulsar properties exclude times wide range $$10^{5}\,\text {year}< \tau _\varepsilon < 10^{15}\,\text {year}$$ 10 5 year < τ ε 15 . For short times, $$\tau 10^5$$ year, different same have radii, depending their age, which possibility tested NICER measurements. also discuss subtleties related with possible existence implications for gravitational waves mergers associated electromagnetic signals.