  We measure the sky-projected stellar obliquities (\lambda) in the
multiple-transiting planetary systems KOI-94 and Kepler-25, using the
Rossiter-McLaughlin effect. In both cases the host stars are well-aligned with
the orbital planes of the planets. For KOI-94 we find \lambda=-11+-11 deg,
confirming a recent result by Hirano and coworkers. Kepler-25 was a more
challenging case because the transit depth is unusually small (0.13 %). To
obtain the obliquity it was necessary to use prior knowledge of the star's
projected rotation rate, and apply two different analysis methods to
independent wavelength regions of the spectra. The two methods gave consistent
results, \lambda=7+-8 deg and -0.5+-5.7 deg.
  There are now a total of five obliquity measurements for host stars of
systems of multiple transiting planets, all of which are consistent with
spin-orbit alignment. This alignment is unlikely to be the result of tidal
interactions, because of the relatively large orbital distances and low
planetary masses in the systems. In this respect the multiplanet host stars
differ from hot-Jupiter host stars, which commonly have large spin-orbit
misalignments whenever tidal interactions are weak. In particular the weak-tide
subset of hot-Jupiter hosts have obliquities consistent with an isotropic
distribution (p=0.6), but the multiplanet hosts are incompatible with such a
distribution (p~10^-6). This suggests that high obliquities are confined to
hot-Jupiter systems, and provides further evidence that hot Jupiter formation
involves processes that tilt the planetary orbit.

Solar and Stellar Astrophysics;Earth and Planetary Astrophysics