We present a numerical Magnetohydrodynamic (MHD) study of the dependence of
stellar mass and angular momentum- loss rates on the orbital distance to
close-in giant planets. We find that the mass loss rate drops by a factor of
≈1.5-2, while the angular momentum loss rate drops by a factor of
≈4 as the distance decreases past the Alfv\'en surface. This reduction
in angular momentum loss is due to the interaction between the stellar and
planetary Alfv\'en surfaces, which modifies the global structure of the stellar
corona and stellar wind on the hemisphere facing the planet, as well as the
opposite hemisphere. The simulation also shows that the magnitude of change in
angular momentum loss rate depends mostly on the strength of the planetary
magnetic field and not on its polarity. The interaction however, begins at
greater separation if the overall field topology of the star and the planet are
of anti-aligned. Our results are consistent with evidence for excess angular
momentum in stars harboring close-in giant planets, and show that the reduction
in wind-driven angular momentum loss can compete with, and perhaps dominate,
spin-up due to tidal interaction.Comment: 6 pages, 3 figure
