The effect of stellar activity on the spectroscopic stellar parameters of the young solar twin HIP 36515

TL;DR

This study investigates how magnetic activity influences spectroscopic stellar parameters and chemical abundances in the young solar twin HIP 36515 over its 6-year activity cycle, revealing strong correlations with activity levels.

Contribution

First analysis of activity cycle effects on stellar parameters and abundances in a young solar twin using high-resolution spectra, challenging assumptions of spectroscopic equilibrium validity.

Findings

Stellar activity correlates with effective temperature, metallicity, and microturbulence.

Li I 6707.8 Å line variations are offset by temperature changes, keeping Li abundance constant.

No significant change in Li abundance over the activity cycle.

Abstract

Spectroscopic equilibrium allows us to obtain precise stellar parameters in Sun-like stars. It relies on the assumption of the iron excitation and ionization equilibrium. However, several works suggest that magnetic activity may affect chemical abundances of young active stars, calling into question the validity of this widely-used method. We have tested for the first time variations in stellar parameters and chemical abundances for the young solar twin HIP 36515 ($\sim$0.4 Gyr), along its activity cycle. This star has stellar parameters very well established in the literature and we estimated its activity cycle in $\sim$6 years. Using HARPS spectra with high resolving power (115 000) and signal-to-noise ratio ($\sim$270), the stellar parameters of six different epochs in the cycle were estimated. We found that the stellar activity is strongly correlated with the effective temperature, metallicity, and microturbulence velocity. The possibility of changes in the Li I 6707.8 \AA line due to flares and star spots was also investigated. Although the core of the line profile shows some variations with the stellar cycle, it is compensated by changes in the effective temperature, resulting in a non variation of the Li abundance.