Chromospheric modeling of the active M3V star G 80-21 with RH1.5D

TL;DR

This paper models the chromospheric active regions of the M3V star G 80-21 using synthetic spectra and observed data, revealing the structure, size, and distribution of active areas through spectral fitting.

Contribution

It introduces a method to determine the structure and size of stellar chromospheric active regions by fitting high-resolution spectra with combined active and inactive models.

Findings

Minor active regions are about 18% of the star, likely in polar areas.

Major active regions vary from 51% to 82% of the star.

The model successfully fits observed spectra across different ratios.

Abstract

This study investigates the active regions of the M3.0V star G 80-21 using the observed data from the CARMENES project with synthetic spectra generated by the RH1.5D radiative transfer code. The CARMENES project aims to search for exoplanets around M dwarfs using high-resolution near-infrared and optical echelle spectrographs. By comparing the observed data and models for the chromospheric lines of H$_\alpha$ and the bluest Ca II infrared triplet line, we obtain the best-fit models for this star. The optimal fitting for the observed spectrum of G 80-21 is achieved by employing two active areas in conjunction with an inactive regions, with a calcium abundance of [Ca/H] = $-$0.4. This combination successfully fits all the observed data across varying ratios. The minor active component consistently comprises approximately 18\% of the total (ranging from 14\% to 20\%), which suggests that the minor active component is likely located in the polar regions. Meanwhile, the major active component occupies a variable proportion, ranging from 51\% to 82\%. Our method allows for the determination of the structure and size of stellar chromospheric active regions by analyzing high-resolution observed spectra.