AAS 205th Meeting, 9-13 January 2005
Session 11 Brown Dwarfs and Exoplanets
Poster, Monday, January 10, 2005, 9:20am-6:30pm, Exhibit Hall

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[11.23] Magnetic Interaction between Stars and Hot Jupiters as Observed in Ca II H & K Emission - An Update

E. Shkolnik (NRC/HIA), G.A.H. Walker (University of British Columbia), D.A. Bohlender (NRC/HIA), P.-G. Gu (Academia Sinica), M. Kürster (Max-Planck-Institut für Astronomie)

We monitored the chromospheric activity in the Ca II H & K lines of 13 solar-type stars (including the Sun); 8 of them over three years at the CFHT and 5 in a single run at the VLT. Ten of the 13 targets have close planetary companions. All of the stars observed at the CFHT show long-term (months to years) changes in H & K intensity levels. Four stars display short-term (days) cyclical activity. For two, HD~73256 and \kappa1~Ceti, the activity is likely associated with an active region rotating with the star, however, the flaring in excess of the rotational modulation may be associated with a hot jupiter. A planetary companion remains an unconfirmed possibility for \kappa1~Ceti. For the other two, HD~179949 and \upsilon And, the cyclic variation is synchronized to the hot jupiter's orbit. For both stars this synchronicity with the orbit is clearly seen in two out of three epochs. The effect is only marginal in the third epoch at which the seasonal level of chromospheric activity had changed for both stars. Short-term chromospheric activity appears weakly dependent on the mean K-line reversal intensities for the sample of 13 stars. Also, a suggestive correlation exists with the Mpsini of the star's hot jupiter. Because of their small separation (\leq 0.1 AU), hot jupiters lie within the Alfvén radius of their host stars which allows a direct magnetic interaction with the stellar surface. This work opens up the possibility of characterizing planet-star interactions with implications for extrasolar planet magnetic fields.

The author(s) of this abstract have provided an email address for comments about the abstract: evgenya.shkolnik@nrc.ca

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© 2004. The American Astronomical Society.