We present six epochs of spectropolarimetric observations of the hot-Jupiter-hosting star τ Bo\"otis that extend the exceptional previous multi-year data set of its large-scale magnetic field. Our results confirm that the large-scale magnetic field of τ Bo\"otis varies cyclicly, with the observation of two further magnetic reversals; between December 2013 and May 2014 and between January and March 2015. We also show that the field evolves in a broadly solar-type manner in contrast to other F-type stars. We further present new results which indicate that the chromospheric activity cycle and the magnetic activity cycles are related, which would indicate a very rapid magnetic cycle. As an exemplar of long-term magnetic field evolution, τ Bo\"otis and this longterm monitoring campaign presents a unique opportunity for studying stellar magnetic cycles.
@article{arxiv.1604.02501,
title = {The Evolving Magnetic Topology of $\tau$ Bo\"otis},
author = {M. W. Mengel and R. Fares and S. C. Marsden and B. D. Carter and S. V. Jeffers and P. Petit and J. -F. Donati and C. P. Folsom and the BCool Collaboration},
journal= {arXiv preprint arXiv:1604.02501},
year = {2016}
}
Comments
20 Pages, 17 figures, accepted for publication in MNRAS