# Coronae of Zero/Low-Metal Low-Mass Stars

## TL;DR

This study uses magnetohydrodynamical simulations to explore how metallicity affects the coronal properties of low-mass stars, revealing that zero-metal stars have significantly hotter, denser coronae with higher UV and X-ray fluxes.

## Contribution

It provides the first detailed simulation-based analysis of coronal heating and properties in low-mass zero-metal stars, highlighting the impact of metallicity on stellar coronae.

## Key findings

- Zero-metal stars have over ten times higher coronal density than solar-metallicity stars.
- Coronal temperatures and densities increase as metallicity decreases.
- UV and X-ray fluxes from zero-metal stars are 1-5 times higher than those from solar-metallicity stars.

## Abstract

Recent theoretical studies suggest the existence of low-mass zero-metal stars in the current universe. In order to study the basic properties of the atmosphere of low-mass first stars, we performed 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 Alfvenic waves originating from the convective motion irrespectively of the 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 ten times higher coronal density than the solar-metallicity counterpart, and as a result, the UV and X-ray fluxes from the loop are (1-5) 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