Evaluating the chromospheric structure model of AD Leo using RH1.5D and magnetic field data

TL;DR

This study combines spectroscopic modeling and magnetic field maps to map the chromospheric structure of AD Leo, revealing the relationship between magnetic flux distribution and emission-line formation in active M dwarfs.

Contribution

It introduces a method that integrates Zeeman-Doppler imaging with multi-component chromospheric modeling to analyze stellar magnetic and chromospheric structures.

Findings

The model accurately reproduces spectral line profiles across epochs.

Active regions account for 55-86% of emission, with temperature variations over time.

Spatial locations of active regions match magnetic field distributions from ZDI.

Abstract

Context. The interplay between surface magnetic topology and chromospheric heating in active M dwarfs remains poorly constrained, limiting our understanding of their magnetic cycles and high-energy environments. Aims. We aim to test whether detailed Zeeman-Doppler imaging (ZDI) maps of AD Leo can be used to spatially anchor a multi-component chromospheric model and validate the link between magnetic flux distribution and emission-line formation. Methods. We analyze high-resolution CARMENES spectra of H-alpha and the Ca II infrared triplet, together with ZDI maps. Synthetic profiles are computed using the RH1.5D non-LTE radiative transfer code with two active atmospheric components (low-latitude near the equator and polar near the pole) and a quiet background. Their relative filling factors and temperature structures are optimized per epoch. The ZDI maps serve as qualitative references for the large-scale magnetic topology but are not used as input to the optimization. Results. Our model reproduces the spectral line profiles across multiple epochs. The low-latitude active region shows notable variability, accounting for approximately 55-86% of the emission, while the polar region remains relatively constant in area (12-17%) but exhibits temperature variations over time, particularly during periods of increased activity. The spatial locations of the active regions derived from spectroscopy agree well with the radial magnetic field distribution from ZDI. Conclusions. Combining spectroscopic modeling with magnetic field maps is an effective approach for mapping magneto-chromospheric structures in M dwarfs. This framework deepens our understanding of stellar magnetic cycles and chromospheric dynamics, paving the way for detailed time-resolved studies in active low-mass stars.