Magnetic field evolution of the K2 dwarf V471 Tau

TL;DR

This study analyzes the magnetic field and surface brightness of the K2 dwarf in V471 Tau using spectropolarimetric data to investigate its potential role in causing observed eclipse timing variations over a ~35-year cycle.

Contribution

It provides new Zeeman-Doppler Imaging reconstructions of the star's magnetic field at a different phase of its activity cycle, offering insights into magnetic mechanisms behind ETVs.

Findings

Reconstructed magnetic field and brightness distribution of the K2 dwarf.

Probed a new phase of the star's activity cycle.

Provided constraints for future studies on magnetic influence on ETVs.

Abstract

Observations of the eclipsing binary system V471 Tau show that the time of the primary eclipses varies in an apparent periodic way. With growing evidence that the magnetically active K2 dwarf component might be responsible for driving the eclipse timing variations (ETVs), it is necessary to monitor the star throughout the predicted ~ 35 yr activity cycle that putatively fuels the observed ETVs. We contribute to this goal with this paper by analysing spectropolarimetric data obtained with ESPaDOnS at the Canada-France-Hawaii Telescope in December 2014 and January 2015. Using Zeeman-Doppler Imaging, we reconstruct the distribution of brightness inhomogeneities and large-scale magnetic field at the surface of the K2 dwarf. Compared to previous tomographic reconstructions of the star carried out with the same code, we probe a new phase of the ETVs cycle, offering new constraints for future works exploring whether a magnetic mechanism operating in the K2 dwarf star is indeed able to induce the observed ETVs of V471 Tau.