Tidal effects on stellar activity

Abstract

Abstract. The architecture of many exoplanetary systems is different from the solar system, with exoplanets being in close orbits around their host stars and having orbital periods of only a few days. We can expect interactions between the star and the exoplanet for such systems that are similar to the tidal interactions observed in close stellar binary systems. For the exoplanet, tidal interaction can lead to circularization of its orbit and the synchronization of its rotational and orbital period. For the host star, it has long been speculated if significant angular momentum transfer can take place between the planetary orbit and the stellar rotation. In the case of the Earth-Moon system, such tidal interaction has led to an increasing distance between Earth and Moon. For stars with Hot Jupiters, where the orbital period of the exoplanet is typically shorter than the stellar rotation period, one expects a decreasing semimajor axis for the planet and enhanced stellar rotation, leading to increased stellar activity. Also excess turbulence in the stellar convective zone due to rising and subsiding tidal bulges may change the magnetic activity we observe for the host star. I will review recent observational results on stellar activity and tidal interaction in the presence of close-in exoplanets, and discuss the effects of enhanced stellar activity on the exoplanets in such systems.

Chromospheric Activity of HAT-P-11: An Unusually Active Planet-hosting K Star

“…Alternative activity indicators have been used to search for evidence that tidal interactions stoke stellar activity (see reviews by Wright and Miller 2015;Poppenhaeger 2017). For example, Poppenhaeger and Wolk (2014) and Miller et al (2015) found enhanced stellar coronal Xray emission from host stars that are expected to have strong tidal interactions with their hot Jupiters.…”