Surface magnetic fields on two accreting T Tauri stars: CV Cha and CR Cha

TL;DR

This study maps the magnetic and brightness features of two young accreting T Tauri stars, revealing complex magnetic fields likely influenced by their internal structure, and compares them with other similar stars.

Contribution

It provides detailed magnetic and brightness maps of CV Cha and CR Cha, showing their complex magnetic fields and exploring the relation to stellar internal structure.

Findings

Magnetic fields are complex and multi-polar, similar to rapidly rotating main sequence stars.

Brightness maps show dark polar caps and low-latitude spots, consistent with other pre-main sequence stars.

Magnetic complexity correlates with the presence of a radiative core in T Tauri stars.

Abstract

We have produced brightness and magnetic field maps of the surfaces of CV Cha and CR Cha: two actively accreting G and K-type T Tauri stars in the Chamaeleon I star-forming cloud with ages of 3-5 Myr. Our magnetic field maps show evidence for strong, complex multi-polar fields similar to those obtained for young rapidly rotating main sequence stars. Brightness maps indicate the presence of dark polar caps and low latitude spots -- these brightness maps are very similar to those obtained for other pre-main sequence and rapidly rotating main sequence stars. Only two other classical T Tauri stars have been studied using similar techniques so far: V2129 Oph and BP Tau. CV Cha and CR Cha show magnetic field patterns that are significantly more complex than those recovered for BP Tau, a fully convective T Tauri star. We discuss possible reasons for this difference and suggest that the complexity of the stellar magnetic field is related to the convection zone; with more complex fields being found in T Tauri stars with radiative cores (V2129 Oph, CV Cha and CR Cha). However, it is clearly necessary to conduct magnetic field studies of T Tauri star systems, exploring a wide range of stellar parameters in order to establish how they affect magnetic field generation, and thus how these magnetic fields are likely to affect the evolution of T Tauri star systems as they approach the main sequence.