摘要：Aims. Several studies suggest that the activity level of a planet-host
star can be influenced by the presence of a close-by orbiting planet. Moreover, the
interaction mechanisms that have been proposed, magnetic interaction and tidal
interaction, exhibit a very different dependence on the orbital separation between the
star and the planet. A detection of activity enhancement and characterization of its
dependence on planetary orbital distance can, in principle, allow us to characterize the
physical mechanism behind the activity enhancement.
Methods. We used the HARPS-N spectrograph to measure the stellar
activity level of HD 80606 during the planetary periastron passage and compared the
activity measured to that close to apastron. Being characterized by an eccentricity of
0.93 and an orbital period of 111 days, the system’s extreme variation in orbital
separation makes it a perfect target to test our hypothesis.
Results. We find no evidence for a variation in the activity level of
the star as a function of planetary orbital distance, as measured by all activity
indicators employed: log(\hbox{$R'_{HK}$}), Hα, NaI, and HeI. None of the models
employed, whether magnetic interaction or tidal interaction, provides a good description
of the data. The photometry revealed no variation either, but it was strongly affected by
poor weather conditions.
Conclusions. We find no evidence for star-planet interaction in HD 80606
at the moment of the periastron passage of its very eccentric planet. The straightforward
explanation for the non-detection is the absence of interaction as a result of a low
magnetic field strength on either the planet or the star and of the low level of tidal
interaction between the two. However, we cannot exclude two scenarios: i) the interaction
can be instantaneous and of magnetic origin, being concentrated on the substellar point
and its surrounding area; and ii) the interaction can lead to a delayed activity
enhancement. In either scenario, a star-planet interaction would not be detectable with
the dataset described in this paper.
关键词：stars: activity;stars: individual: HD 80606;instrumentation: spectrographs;techniques: radial velocities;techniques: spectroscopic;methods: data analysis
