Contributed Talk - Splinter Stellar

Friday, 25 September 2020, 09:38   (virtual room M)

Measuring the tidal interaction footprint on stellar magnetic activity in star-planet systems

Nikoleta Ilic, Katja Poppenhaeger
Leibniz Institut fuer Astrophysik Potsdam (AIP)

It is an open question to what degree planets influence the (magnetic) evolution of their host star. We investigate the tidal interaction in star-planet systems, which reside in binary or multiple stellar systems, by comparing the magnetic activity level of the planet host with the stellar companion's activity. As a star ages and evolves, its rotational rate decreases and the star spins down. The increase in stellar rotational period results from the angular momentum loss due to the process called magnetic braking. This is the usual 'spin-down' scenario for singular stars and stars without planets. In star-planet systems, the possibility of halting the decrease or even increasing the rotational rate of a star due to tidal interaction with its planet(s) exists. This tidal 'spin-up' can be traced by an enhanced magnetic activity since a faster rotating star is expected to be more magnetically active. The difficulty here is estimating if the observed magnetic activity level of the star is higher due to the tidal interaction with the planet or due to the relatively young age, when the process of magnetic braking is still undergoing. Our solution for this is to invoke a reference star that does not host a planet and that has the same age as the planet-hosting star. Therefore, we analyse wide binary and multiple stellar systems that have a planet-hosting star and use its coeval stellar companion as a proxy for the expected magnetic activity level. We have a sample of 37 stellar systems, observed in X-rays with XMM Newton and Chandra, for which we evaluate the component' X-ray luminosity. We expect that the enhanced magnetic activity of the planet host leads to a hotter corona and hence a brighter X-ray source when compared to its stellar companion, if the enhancement is due to tidal interaction. With this approach, we will be able to determine if the tidal 'spin-up' process can leave an observable footprint on planet-hosting stars and which star-planet system configuration is prone to significantly changing the activity level of the star.