The weak-line T Tauri star V410Tau I. A multi-wavelength study of variability

TL;DR

This study investigates magnetic activity indicators in the pre-main sequence star V410Tau through coordinated optical and X-ray observations, revealing complex variability patterns and suggesting a possible 5.4-year activity cycle.

Contribution

It provides the first evidence of a potential activity cycle in a pre-main sequence star by combining multi-year optical and X-ray data.

Findings

No clear correlation between X-ray levels and optical rotation phase.

The largest star spot remains remarkably stable over years.

A possible 5.4-year activity cycle is identified.

Abstract

We present the results of an intensive coordinated monitoring campaign in the optical and X-ray wavelength ranges of the low-mass, pre-main sequence star V410Tau carried out with the aim to study the relation between various indicators for magnetic activity that probe emission from different atmospheric layers: optical photometric star spot (rotation) cycle, chromospheric Halpha emission, and coronal X-rays. Two X-ray pointings were carried out with the Chandra satellite simultaneously with the optical observations, and centered near the maximum and minimum levels of the optical lightcurve. A relation of their different count levels to the rotation period of the dominating spot is not confirmed by a third Chandra observation carried out some months later, during another minimum of the 1.87d cycle. Similarly we find no indications for a correlation of the Halpha emission with the spots' rotational phase. The extraordinary stability of the largest spot is confirmed by long-term photometric and radial velocity measurements. Joining our optical photometry with previous data we provide a new estimate for the dominant periodicity of V410Tau. This updated value removes systematic offsets of the time of minimum observed in data taken over the last decade. Furthermore, the combination of the new data with published measurements taken during the last decade allows us to examine long-term changes in the mean light level of the photometry of V410Tau. A variation on the timescale of 5.4yr is suggested. Assuming that this behavior is truely cyclic V410Tau is the first pre-main sequence star on which an activity cycle is detected.