Stellar activity and Lithium abundances in exoplanets host stars

MAUAS, P. J. D.; BUCCINO, A.P.; SAFFE, C; FLORES, M.

Moscú

Congreso; 40th COSPAR Scientific Assembly; 2014

COSPAR

To date, the developed theory proposes that the star-planet interactions (SPI) could be of magnetic origin, through the magnetosphere of the exoplanet, or mechanical origin, where tidal forces are involved in the interactions. Both processes could increase the activity level of the host stars. As a contribution on this discussion, we analyzed the possible relation between stellar activity and some planetary parameters (semi-major axis, planet mass, orbital period). Our observations were made at the 2.15 m telescope of the Complejo Astronómico El Leoncito (CASLEO), which is located at 2552 m above sea level, in the Argentinean Andes. We studied the long-term activity of stars with planets. We used as activity indicator the well-known Mount Wilson index (S) derived from the mid-resolution CASLEO spectra. Furthermore, we took cuasisimultaneous spectra of stars without planets with the same spectral class, to compare activity levels. Moreover, we also studied the excess of Lithium (Li) depletion registered in stars with planets compared to stars without planets of similar parameters (such as Teff and log g), and its possible relation with the stellar activity. It is believed, that the stellar rotation is the most important parameter to determine the surface Li content, because the Li loss mechanism caused by the mixing envelope operates more efficiently as stellar rotation decreases. If this interpretation is correct, would be possible to explain the apparent excess of Li depletion in stars with planets when they are compared with field stars. A planetary system may alter the evolution of the angular momentum of the star and the surface convective mixing, thus causing the excess of Li depletion. To do so, we used high-resolution spectra (R=110.000) of FGK stars with and without planets taken with the HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph, installed at the 3.6 m ESO telescope. Then, we ajust the Li (670.78 nm) line by synthetic spectra calculated with SYNTHE for the stars with and without planets from our