A possible long-term activity cycle for iota Horologii: First results from SPI-HKa project

FLORES, MATÍAS; BUCCINO, A.; SAFFE, CARLOS; MAUAS, P.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2017 vol. 464 p. 4299 - 4305

0035-8711

In order to detect stellar activity cycles and study possible star?planet interactions (SPIs), we have been developing the HKα and SPI-HKα projects since 1999 and 2012 respectively. In this work, we present preliminary results of possible SPIs from studies of chromospheric activity and look for possible correlations between stellar activity and stellar/planetary parameters. We find that for stars with a similar Teff, stellar activity increases with the mass of the planet, similar to results from previous works. However, stellar ages can also play a role, and a larger stellar sample is needed to verify these trends.We also note that some of these stars present a remarkably high level of chromospheric activity, comparable even with RSCvn or BY Dra active stars. In addition, we do not observe any correlation between stellar activity and semi-major axis. We present the first long-term activity study of the star iota Horologii, a young solar-type star that hosts a non-transiting Jovian planet and exhibits a high activity level. We analysed our own spectra,obtained between 2002 and 2015, in conjunction with public HARPS (High Accuracy Radial velocity Planet Searcher) observations. We calculated the Ca II indexes derived from the 987 Complejo Astronómico El Leoncito (CASLEO) and HARPS spectra and converted them to the Mt Wilson scale. We found a long-term activity cycle of ∼5 yr which fits the active sequence of Böhm-Vitense. The amplitude of this longer cycle is irregular, as was also observed for the shorter cycle. This phenomenon could be attributable to an antisymmetric distribution of active regions on the stellar surface.