Cool Stars 14 - Submitted Abstract # 160
This version created on 05 October 2006

Exoplanet-Induced Chromospheric Activity:  Realistic Light Curves from
Solar-type Magnetic Fields


Steven R. Cranmer, Harvard-Smithsonian Center for Astrophysics
Steven H. Saar, Harvard-Smithsonian Center for Astrophysics

There is growing observational evidence for some kind of interaction
between stars and close-in extrasolar giant planets.  Shkolnik et al.
reported variability in the chromospheric Ca H and K lines of HD
179949 and upsilon And that seemed to be phased with the planet's
orbital period, instead of the stellar rotational period.  However,
the observations also indicate that the chromospheric light curves do
not repeat exactly, which may be expected for a planet plowing through
a slowly varying stellar magnetic field.  Using the complex solar
magnetic field (modeled with the Potential Field Source Surface
technique) as a guide, we simulate the shapes of light curves that
would arise from planet-star interactions that are channeled along
magnetic field lines.  We also study the orbit-to-orbit variability of
these light curves and how they vary from solar minimum (i.e., a more
or less axisymmetric stretched dipole) to solar maximum (a
superposition of many higher multipole moments) fields.  Considering
more complex magnetic fields introduces new difficulties in the
interpretation of observations, but it may also lead to valuable new
diagnostics of exoplanet magnetospheres.

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