  The shape of the Ti I 6303.8 A spectral line of Aldebaran as measured by the
line bisector was investigated using high signal-to-noise, high resolution
data. The goal of this study was to understand the nature of the 643-day period
in the radial velocity for this star reported by Hatzes and Cochran. Variations
in the line bisector with the radial velocity period would provide strong
evidence in support of rotational modulation or stellar pulsations as the cause
of the 643-day period. A lack of any bisector variability at this period would
support the planet hypothesis. Variations in the line asymmetries are found
with a period of 49.93 days. These variations are uncorrelated with 643-day
period found previously in the radial velocity measurements. It is demonstrated
that this 50-day period is consistent with an m=4 nonradial sectoral g-mode
oscillation. The lack of spectral variability with the radial velocity period
of 643 days may provide strong evidence in support of the hypothesis that this
variability stems from the reflex motion of the central star due to a planetary
companion having a mass of 11 Jupiter masses. However, this long-period
variability may still be due to a low order (m=2) pulsation mode since these
would cause bisector variations less than the error measurement.

Astrophysics