Dynamo Processes in the T Tauri star V410 Tau

TL;DR

This study provides detailed brightness and magnetic maps of the T Tauri star V410 Tau, revealing a predominantly dipolar magnetic field and a large polar spot, and discusses the relationship between spot distribution and photometric variability.

Contribution

First Zeeman-Doppler imaging campaign on V410 Tau, offering new magnetic and brightness maps and insights into spot distribution and magnetic topology changes over time.

Findings

Star has a predominantly dipolar, non-axisymmetric magnetic field.

Large polar spot and low variability in 2009 observed.

Spot distribution changes may explain photometric variability variations.

Abstract

We present new brightness and magnetic images of the weak-line T Tauri star V410 Tau, made using data from the NARVAL spectropolarimeter at Telescope Bernard Lyot (TBL). The brightness image shows a large polar spot and significant spot coverage at lower latitudes. The magnetic maps show a field that is predominantly dipolar and non-axisymmetric with a strong azimuthal component. The field is 50% poloidal and 50% toroidal, and there is very little differential rotation apparent from the magnetic images. A photometric monitoring campaign on this star has previously revealed V-band variability of up to 0.6 magnitudes but in 2009 the lightcurve is much flatter. The Doppler image presented here is consistent with this low variability. Calculating the flux predicted by the mapped spot distribution gives an peak-to-peak variability of 0.04 magnitudes. The reduction in the amplitude of the lightcurve, compared with previous observations, appears to be related to a change in the distribution of the spots, rather than the number or area. This paper is the first from a Zeeman-Doppler imaging campaign being carried out on V410 Tau between 2009-2012 at TBL. During this time it is expected that the lightcurve will return to a high amplitude state, allowing us to ascertain whether the photometric changes are accompanied by a change in the magnetic field topology.