Abstract
We present new brightness and magnetic images of the weak-line T Tauri star V410 Tau, made by using data from the Narval spectropolarimeter at Télescope 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 per cent poloidal and 50 per cent toroidal, and very little differential rotation is apparent from the magnetic images. A photometric monitoring campaign on this star has previously revealed V-band variability of up to 0.6 mag, but in 2009 the light curve is much flatter. The Doppler image presented here is consistent with this low variability. Calculating the flux predicted by the mapped spot distribution gives a peak-to-peak variability of 0.04 mag. The reduction in the amplitude of the light curve, 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 and 2012 at the TBL. During this time, it is expected that the light curve 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.
Highlights
T Tauri stars (TTS) are pre-main sequence late-type stars
While the qualitative similarity of the field with those of partially–convective stars such as AB Dor suggests that V410 Tau has a radiative core, we cannot rule out the possibility that V410 Tau is fully convective, as Sec. 2 suggested
The Doppler image of the weak-line T Tauri star V410 Tau in January 2009 shows a large polar spot and a several lower latitude spots spread around the latitude band between 0 − 30◦
Summary
T Tauri stars (TTS) are pre-main sequence late-type stars. As they contract towards the main sequence the increasing density in their interiors will lead to the development of a radiative core, if the star is sufficiently massive. It is a weak-line T Tauri star (wTTS) which has already dissipated its disk, it does not display signatures of accretion characteristic of classical TTS (cTTS) It has a v sin i of 74 ± 3 km s−1 and a period of 1.872 days (Stelzer et al 2003), and is an example of the young, rapidly rotating stars which are characterised by strong, large scale magnetic fields. V410 Tau is the target of an ongoing photometric monitoring campaign which began in 1981 (Vrba et al 1988; Herbst 1989; Petrov et al 1994; Grankin et al 2008) For most of this time the lightcurve has been smooth, repeating, with a clearly defined period and an amplitude between 0.2 and 0.6 magnitudes.
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