Stellar chromospheric activity database of solar-like stars based on the LAMOST Low-Resolution Spectroscopic Survey

II. The bolometric and photospheric calibration^★

¹ School of Physics and Optoelectronic Engineering, Anhui University, Hefei 230601, PR China
e-mail: zjun@ahu.edu.cn
² National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, PR China
e-mail: hehan@nao.cas.cn
³ University of Chinese Academy of Sciences, Beijing 100049, PR China
⁴ CAS Key Laboratory of Optical Astronomy, Chinese Academy of Sciences, Beijing 100101, PR China

Received: 18 December 2023
Accepted: 15 May 2024

Abstract

Context. The dependence of stellar magnetic activity on stellar parameters is inspired by the chromospheric activity studies based on the large-scale spectroscopic surveys.

Aims. The main objective of this project is to provide the chromospheric activity parameter database for the LAMOST Low-Resolution Spectroscopic Survey (LRS) spectra of solar-like stars and explore the overall property of stellar chromospheric activity.

Methods. The Ca II H and K lines were employed to construct indicators for assessing and studying the chromospheric activity of solar-like stars. We investigated the widely used bolometric- and photospheric-calibrated chromospheric activity index R′_HK, derived from the method in the classic literature (R′_HK,classic) and the method based on the PHOENIX model (R′_HK,PHOENIX). Since the detailed stellar atmospheric parameters, effective temperature (T_eff), surface gravity (log g), and metallicity ([Fe/H]) are available for LAMOST, we estimated the chromospheric activity index R′_HK,PHOENIX, along with the corresponding bolometric calibrated index R_HK,PHOENIX, taking these parameters into account.

Results. We provided 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′_HK,PHOENIX is approximately linearly correlated with log R′_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 the solar chromospheric activity index is located at the midpoint of the solar-like star sample. We further investigated 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 K.