Synthetic polarimetric spectra from stellar prominences

TL;DR

This paper models the polarization signatures of stellar prominences in specific spectral lines, revealing how magnetic fields influence observable signals, and discusses potential detection with future instruments.

Contribution

It introduces a detailed synthesis of polarization profiles in stellar prominences considering magnetic effects, aiding future observational efforts.

Findings

Linear polarization signals are generated by scattering and modified by the Hanle effect.

Zeeman effect produces low-amplitude Stokes V signals when magnetic fields are present.

Predicted polarization signals could be detectable with upcoming spectropolarimeters.

Abstract

Stellar prominences detected in rapidly rotating stars serve as probes of the magnetism in the corona of cool stars. We have synthesized the temporal evolution of the Stokes profiles generated in the He I 10830 and 5876 A triplets during the rotation of a prominence around a star. The synthesis was performed with the HAZEL code using a cloud model in which the prominence is characterized by a slab located at a fixed latitude and height. It accounts for the scattering polarization and Zeeman and Hanle effects. Several cases with different prominence magnetic field strengths and orientations have been analyzed. The results show an emission feature that drifts across the profile while the prominence is out of the stellar disk. When the prominence eclipses the star, the intensity profile shows an absorption. The scattering induced by the prominence generates linear polarization signals in Stokes Q and U profiles, which are modified by the Hanle effect when a magnetic field is present. Due to the Zeeman effect, Stokes V profiles show a signal with very low amplitude when the magnetic field along the line-of-sight is different from zero. The estimated linear polarization signals could potentially be detected with the future spectropolarimeter MIRADAS, to be attached to GTC telescope.