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

Teruyuki Hirano, Roberto Sanchis-Ojeda, Yoichi Takeda, Joshua N. Winn, Norio Narita, Yasuhiro H. Takahashi

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

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.

Original languageEnglish (US)
Article number9
JournalAstrophysical Journal
Volume783
Issue number1
DOIs
StatePublished - Mar 1 2014
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • planets and satellites: formation
  • planets and satellites: general
  • stars: rotation
  • techniques: spectroscopic

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