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Title: Measurements of stellar inclinations for Kepler planet candidates. II. Candidate spin-orbit misalignments in single- and multiple-transiting systems

We present a test for spin-orbit alignment for the host stars of 25 candidate planetary systems detected by the Kepler spacecraft. The inclination angle of each star's rotation axis was estimated from its rotation period, rotational line broadening, and radius. The rotation periods were determined using the Kepler photometric time series. The rotational line broadening was determined from high-resolution optical spectra with the Subaru High Dispersion Spectrograph. Those same spectra were used to determine the star's photospheric parameters (effective temperature, surface gravity, metallicity), which were then interpreted with stellar-evolutionary models to determine stellar radii. We combine the new sample with the seven stars from our previous work on this subject, finding that the stars show a statistical tendency to have inclinations near 90°, in alignment with the planetary orbits. Possible spin-orbit misalignments are seen in several systems, including three multiple-planet systems (KOI-304, 988, 2261). Ideally, these systems should be scrutinized with complementary techniques, such as the Rossiter-McLaughlin effect, starspot-crossing anomalies, or asteroseismology, but the measurements will be difficult owing to the relatively faint apparent magnitudes and small transit signals in these systems.
Authors:
 [1] ; ;  [2] ; ; ;  [3]
  1. Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)
  2. Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
  3. National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)
Publication Date:
OSTI Identifier:
22351391
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 783; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALIGNMENT; DISPERSIONS; GRAVITATION; HOST; INCLINATION; LINE BROADENING; L-S COUPLING; METALLICITY; ORBITS; PLANETS; RESOLUTION; ROTATION; SATELLITES; SIGNALS; SPECTRA; SPIN; STARS; SURFACES