Evolution of Stellar Activity and Habitable Zone II: Ca H&K Emissions of Late-type Dwarfs

TL;DR

This paper investigates how stellar chromospheric activity, measured via Ca H&K emissions, declines with age in late-type dwarfs, revealing spectral type and metallicity dependencies using LAMOST data.

Contribution

It establishes a Skumanich-type linear relation for activity decline across spectral types and highlights metallicity effects on stellar activity.

Findings

Linear activity-age relation varies with spectral type

Lower-metallicity stars show enhanced activity in F, G, K types

No clear metallicity dependence for M dwarfs

Abstract

Stellar chromospheric activity serves as a valuable proxy for estimating stellar ages, though its applicable range and accurate functional form are still debated. In this study, utilizing the LAMOST spectra we compiled a catalog of open cluster members and field stars to investigate $R_{\rm{HK}}^{'}$--age relations across various spectral types. We find that a linear model, specifically a Skumanich-type relation, can best describe the overall decline of chromospheric activity with age, with the slope varying across different spectral types. However, we also identify variations in the decay rate along the main sequence, which call for more accurate follow-up investigation. Finally, we find that lower-metallicity stars exhibit enhanced activity for F-, G-, and K-type stars, whereas no clear metallicity dependence is observed for M dwarfs.