Coronae of Zero/Low-metal, Low-mass Stars

Abstract

Recent theoretical studies suggest the existence of low-mass, zero-metal stars in the current universe. To study the basic properties of the atmosphere of low-mass first stars, we perform one-dimensional magnetohydrodynamical simulations for the heating of coronal loops on low-mass stars with various metallicities. While the simulated loops are heated up to ≥10 6 K by the dissipation of Alfvénic waves originating from the convective motion irrespective of metallicity, the coronal properties sensitively depend on the metallicity. Lower-metal stars create hotter and denser coronae because the radiative cooling is suppressed. The zero-metal star gives more than 40 times higher coronal density than the solar-metallicity counterpart, and as a result, the UV and X-ray fluxes from the loop are several times higher than those of the solar-metallicity star. We also discuss the dependence of the coronal properties on the length of the simulated coronal loops.