EVIDENCE OF POSSIBLE SPIN–ORBIT MISALIGNMENT ALONG THE LINE OF SIGHT IN TRANSITING EXOPLANET SYSTEMS

By K. Schlaufman. 2010

171 citations recorded by the source corpus.

Of the 26 transiting exoplanet systems with measurements of the Rossiter–McLaughlin (RM) effect, eight have now been found to be significantly spin–orbit misaligned in the plane of the sky (i.e., RM misalignment angle |λ| ≳ 30° and inconsistent with λ = 0°). Unfortunately, the RM effect does not constrain the complement misalignment angle between the orbit of the planet and the spin of its host star along the line of sight (LOS). I use a simple model of stellar rotation benchmarked with observational data to statistically identify 10 exoplanet systems from a sample of 75 for which there is likely a significant degree of spin–orbit misalignment along the LOS: HAT-P-7, HAT-P-14, HAT-P-16, HD 17156, Kepler-5, Kepler-7, TrES-4, WASP-1, WASP-12, and WASP-14. All 10 systems have host stellar masses M* in the range 1.2 M☉ ≲ M* ≲ 1.5 M☉, and the probability of this occurrence by chance is less than one in ten thousand. In addition, the planets in the candidate-misaligned systems are preferentially massive and eccentric. The coupled distribution of misalignment from the RM effect and from this analysis suggests that transiting exoplanets are more likely to be spin–orbit aligned than expected given predictions for a transiting planet population produced entirely by planet–planet scattering or Kozai cycles and tidal friction. For that reason, there are likely two populations of close-in exoplanet systems: a population of aligned systems and a population of apparently misaligned systems in which the processes that lead to misalignment or to the survival of misaligned systems operate more efficiently in systems with massive stars and planets.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/df684245fb1016c433763113bb213f6283f21eb2

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In Astronomy and Astrophysics

1. J. Winn
2. J. Johnson
3. Andrew W. Howard
4. G. Marcy
5. D. Charbonneau
6. Timothy Morton
7. D. Fabrycky
8. T. Mazeh

In Instrumentation

1. J. Winn
2. Andrew W. Howard
3. J. Johnson
4. G. Marcy
5. D. Fabrycky
6. Timothy Morton
7. D. Lai
8. Suzanne Aigrain

Citations in the corpus

• The Occurrence and Architecture of Exoplanetary Systems (2014, background): “If this is significantly smaller than unity for a star with a transiting planet, then the star has a high obliquity (Schlaufman 2010).”
• OBLIQUITIES OF HOT JUPITER HOST STARS: EVIDENCE FOR TIDAL INTERACTIONS AND PRIMORDIAL MISALIGNMENTS (2012, methodology): “(Winn et al. 2009; Schlaufman 2010), but with nearly antiparallel sky projections of the orbital and stellar rotation vectors.”
• MULTIPLE-PLANET SCATTERING AND THE ORIGIN OF HOT JUPITERS (2011, background): “There also seems to be an indication that more circular orbits are accompanied by small values of |λ|, while large values of |λ| appear in more eccentric cases (Schlaufman 2010).”
• INTERNAL GRAVITY WAVES IN MASSIVE STARS: ANGULAR MOMENTUM TRANSPORT (2013, background): “However, hot Jupiters with high Θ are primarily found around stars with effective temperature (T∗) hotter than 6,250K (Winn et al. 2010), while the orbits of hot Jupiters around relatively cool, solarlike, stars are generally aligned with their hosts (Winn et al. 2010; Schlaufman 2010).”
• The Apparently Decaying Orbit of WASP-12b (2017, background): “The star’s equator is likely to be misaligned with the orbital plane (Schlaufman 2010; Albrecht et al. 2012).”
• A STUDY OF THE SHORTEST-PERIOD PLANETS FOUND WITH KEPLER (2014, methodology): “Given a large sample of obserations, thevsini technique can also be used to constrain the statistical properties of the distribution of obliquities for a given family of planets (Schlaufman 2010; Hirano et al. 2012a; Hirano et al. 2014).”
• STELLAR ROTATION PERIODS OF THE KEPLER OBJECTS OF INTEREST: A DEARTH OF CLOSE-IN PLANETS AROUND FAST ROTATORS (2013, methodology): “Schlaufman (2010); Hirano et al. (2012) have used the rotation periods of exoplanet host stars to study spin-orbit misalignment, through measurement of v sin i, to study formation and evolution.”
• Tidal dissipation in planet-hosting stars: damping of spin-orbit misalignment and survival of hot Jupiters (2011, result): “This trend was also found from a recent analysis of the stellar rotation velocities (Schlaufman 2010).”