A small survey of the magnetic fields of planet-host stars

TL;DR

This study uses spectropolarimetry to analyze the magnetic topologies of ten planet-host stars, revealing similarities to stars without hot Jupiters and confirming magnetic polarity reversal in Tau Boo.

Contribution

It provides new magnetic field measurements of ten planet-host stars and reports magnetic polarity reversal in Tau Boo, contributing to understanding star-planet magnetic interactions.

Findings

Magnetic fields detected in 7 stars with reconstructed topologies.

Tau Boo exhibits magnetic polarity reversal, suggesting a 2-year cycle.

Planet-host stars show magnetic properties similar to stars without hot Jupiters.

Abstract

Using spectropolarimetry, we investigate the large-scale magnetic topologies of stars hosting close-in exoplanets. A small survey of ten stars has been done with the twin instruments TBL/NARVAL and CFHT/ESPaDOnS between 2006 and 2011. Each target consists of circular-polarization observations covering 7 to 22 days. For each of the 7 targets in which a magnetic field was detected, we reconstructed the magnetic field topology using Zeeman-Doppler imaging. Otherwise, a detection limit has been estimated. Three new epochs of observations of Tau Boo are presented, which confirm magnetic polarity reversal. We estimate that the cycle period is 2 years, but recall that a shorter period of 240 days can not still be ruled out. The result of our survey is compared to the global picture of stellar magnetic field properties in the mass-rotation diagram. The comparison shows that these giant planet-host stars tend to have similar magnetic field topologies to stars without detected hot-Jupiters. This needs to be confirmed with a larger sample of stars.