The magnetic fields of accreting T Tauri stars

TL;DR

This paper compares the magnetic field structures of two T Tauri stars with different internal structures, showing that realistic complex fields lead to different disk truncation radii than simple dipole models.

Contribution

It provides a comparative analysis of magnetic field extrapolations for two T Tauri stars with different internal structures, highlighting the impact of field complexity on disk truncation.

Findings

Magnetic fields are more complex than simple dipoles.

Disk truncation occurs at or within the radius predicted by dipole models.

Field complexity affects accretion disk interactions.

Abstract

Models of magnetospheric accretion on to classical T Tauri stars often assume that the stellar magnetic field is a simple dipole. Recent Zeeman-Doppler imaging studies of V2129 Oph and BP Tau have shown however that their magnetic fields are more complex. V2129 Oph is a high mass T Tauri star and despite its young age is believed to have already developed a radiative core. In contrast to this, the lower mass BP Tau is likely to be completely convective. As the internal structure and therefore the magnetic field generation process is different in both stars, it is of particular interest to compare the structure of their magnetic fields obtained by field extrapolation from magnetic surface maps. We compare both field structures to mulitpole magnetic fields, and calculate the disk truncation radius for both systems. We find that by considering magnetic fields with a realistic degree of complexity, the disk is truncated at, or within, the radius obtained for dipole fields.