Stellar Chromospheric Activity Database of Solar-like Stars Based on the LAMOST Low-Resolution Spectroscopic Survey: II. the bolometric and photospheric calibration

TL;DR

This study calibrates and compiles a large database of chromospheric activity indices for over a million solar-like stars using LAMOST spectroscopic data, enabling detailed analysis of stellar magnetic activity.

Contribution

It introduces a new calibration method for the $R'_{HK}$ index based on the PHOENIX model and provides an extensive database of activity parameters for solar-like stars.

Findings

$ m log R'_{HK,PHOENIX}$ correlates linearly with $ m log R'_{HK,classic}$

The solar activity index is median among solar-like stars

High activity levels are less common in stars with $5600$-$5900$ K

Abstract

The dependence of stellar magnetic activity on stellar parameters would be inspired by the chromospheric activity studies based on the large-scale spectroscopic surveys. The Ca II H and K lines are employed to construct indicators for assessing and studying the chromospheric activity of solar-like stars. We investigate the widely used bolometric and photospheric calibrated chromospheric activity index $R'_{\rm HK}$, derived from the method in the classic literature ($R'_{\rm HK,classic}$) and the method based on the PHOENIX model ($R'_{\rm HK,PHOENIX}$). Since the detailed stellar atmospheric parameters, effective temperature ($T_{\rm eff}$), surface gravity ($\log\,g$), and metallicity ([Fe/H]), are available for LAMOST, we estimate the chromospheric activity index $R'_{\rm HK,PHOENIX}$, along with the corresponding bolometric calibrated index $R_{\rm HK,PHOENIX}$, taking these parameters into account. We provide the database of the derived chromospheric activity parameters for 1,122,495 LAMOST LRS spectra of solar-like stars. Our calculations show that $\log\,R'_{\rm HK,PHOENIX}$ is approximately linearly correlated with $\log\,R'_{\rm HK,classic}$. The results based on our extensive archive support the view that the dynamo mechanism of solar-like stars is generally consistent with the Sun; and the value of solar chromospheric activity index is located at the midpoint of the solar-like star sample. We further investigate the proportions of solar-like stars with different chromospheric activity levels (very active, active, inactive and very inactive). The investigation indicates that the occurrence rate of high levels of chromospheric activity is lower among the stars with effective temperatures between $5600$ and $5900 \,{\rm K}$.