Stellar chromospheric activity and age relation from open clusters in the LAMOST Survey

TL;DR

This study analyzes the relationship between stellar chromospheric activity and age using open cluster data from the LAMOST survey, establishing empirical relations to estimate stellar ages with reasonable accuracy.

Contribution

It introduces a method to estimate stellar ages from chromospheric activity indices based on a large sample of open cluster stars, improving age determination techniques.

Findings

Chromospheric activity decreases with stellar age, especially for cooler stars.

Quadratic relations between activity indices and age enable age estimation with ~40-60% accuracy.

Activity decline accelerates after a certain stellar age threshold.

Abstract

We identify member stars of more than 90 open clusters in the LAMOST survey. With the method of Fang et al.(2018), the chromospheric activity (CA) indices logR'CaK for 1091 member stars in 82 open clusters and logR'H{\alpha} for 1118 member stars in 83 open clusters are calculated. The relations between the average logR'CaK, logR'H{\alpha} in each open cluster and its age are investigated in different Teff and [Fe/H] ranges. We find that CA starts to decrease slowly from logt = 6.70 to logt = 8.50, and then decreases rapidly until logt = 9.53. The trend becomes clearer for cooler stars. The quadratic functions between logR' and logt with 4000K < Teff < 5500K are constructed, which can be used to roughly estimate ages of field stars with accuracy about 40% for logR'CaK and 60% for logR'H{\alpha}.