The influence of chromospheric activity on line formation

TL;DR

This study investigates how stellar chromospheric activity influences spectral line formation, identifying key spectral regions and lines affected, which aids in interpreting stellar spectra and activity levels.

Contribution

The paper introduces a detailed analysis of activity-induced spectral changes using synthetic models, highlighting specific regions and lines impacted by chromospheric activity.

Findings

Two spectral regions are most affected by activity: 3300-4400 Å and 5250-5500 Å.

Secondary chromospheric contributions significantly influence line formation.

A list of lines with activity-related changes is provided for future studies.

Abstract

One of the primary sources of stellar spectral variability is magnetic activity. While our current understanding of chromospheric activity is largely derived from specific lines sensitive to chromospheric heating, such as the Ca II HK doublet, previous observational studies have shown that other spectral lines are also affected. To investigate the influence of activity on line formation in greater detail, we constructed a set of stellar models for hypothetical G2 dwarf stars with varying levels of activity and calculated their synthetic spectra. A comparison of these spectra revealed two spectral regions most significantly impacted by activity: approximately 3300-4400 A and 5250-5500 A. By calculating the total contribution function of the lines, we determined that the emergence of a secondary chromospheric contribution to line formation is the primary mechanism driving these changes. Based on our calculations and analysis, we compiled a list of transition lines and their corresponding changes due to chromospheric activity. This list could serve as a valuable tool for selecting spectral lines applicable to a wide range of astrophysical studies.