  It has been known for a decade that hot stars with hot Jupiters tend to have
high obliquities. Less is known about the degree of spin-orbit alignment for
hot stars with other kinds of planets. Here, we re-assess the obliquities of
hot Kepler stars with transiting planets smaller than Neptune, based on
spectroscopic measurements of their projected rotation velocities (vsini). The
basis of the method is that a lower obliquity -- all other things being equal
-- causes sini to be closer to unity and increases the value of vsini. We
sought evidence for this effect using a sample of 150 Kepler stars with
effective temperatures between 5950 and 6550K and a control sample of 101 stars
with matching spectroscopic properties and random orientations. The planet
hosts have systematically higher values of vsini than the control stars, but
not by enough to be compatible with perfect spin-orbit alignment. The mean
value of sini is 0.856 +/- 0.036, which is 4-sigma away from unity (perfect
alignment), and 2-sigma away from pi/4 (random orientations). There is also
evidence that the hottest stars have a broader obliquity distribution: when
modeled separately, the stars cooler than 6250K have <sini> = 0.928 +/- 0.042,
while the hotter stars are consistent with random orientations. This is similar
to the pattern previously noted for stars with hot Jupiters. Based on these
results, obliquity excitation for early-G and late-F stars appears to be a
general outcome of star and planet formation, rather than being exclusively
linked to hot Jupiter formation.
