EXOPLANETARY SPIN–ORBIT ALIGNMENT: RESULTS FROM THE ENSEMBLE OF ROSSITER–MCLAUGHLIN OBSERVATIONS

By D. Fabrycky, J. Winn. 2009

182 citations recorded by the source corpus.

One possible diagnostic of planet formation, orbital migration, and tidal evolution is the angle ψ between a planet's orbital axis and the spin axis of its parent star. In general, ψ cannot be measured, but for transiting planets one can measure the angle λ between the sky projections of the two axes via the Rossiter–McLaughlin effect. Here, we show how to combine measurements of λ in different systems to derive statistical constraints on ψ. We apply the method to 11 published measurements of λ, using two different single-parameter distributions to describe the ensemble. First, assuming a Rayleigh distribution (or more precisely, a Fisher distribution on a sphere), we find that the peak value is less than 22° with 95% confidence. Second, assuming that a fraction f of the orbits have random orientations relative to the stars, and the remaining fraction (1 − f) are perfectly aligned, we find f < 0.36 with 95% confidence. This latter model fits the data better than the Rayleigh distribution, mainly because the XO-3 system was found to be strongly misaligned while the other 10 systems are consistent with perfect alignment. If the XO-3 result proves robust, then our results may be interpreted as evidence for two distinct modes of planet migration.

Subfields: Astronomy and Astrophysics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/23965a0e8e1ae014a4e1f1c4cfe00f25f8bc683a

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In Astronomy and Astrophysics

1. J. Winn
2. J. Southworth
3. J. Johnson
4. Jon Fortney
5. G. Marcy
6. D. Charbonneau
7. Timothy Morton
8. Yanqin Wu

In Statistical and Nonlinear Physics

1. Y. Lithwick
2. Yanqin Wu
3. C. Beaugé
4. D. Nesvorný
5. K. Schlaufman
6. Andrew W. Howard
7. J. Winn
8. J. Johnson

Citations in the corpus

• ARCHITECTURE AND DYNAMICS OF KEPLER'S CANDIDATE MULTIPLE TRANSITING PLANET SYSTEMS (2011, background): “The Rayleigh distribution is the appropriate choice for randomly distributed inclination angles (see, e.g., Fabrycky & Winn 2009) and requires a single value to define the distribution.”
• TIDAL EVOLUTION OF CLOSE-IN PLANETS (2010, background): “Thus, from cos ǫ∗ = sin i∗ cosλ sin io+cos i∗ cos io (Fabrycky & Winn 2009), the stellar obliquity becomes comparable to the projected one (ǫ∗ ≃ λ).”
• WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star (2015, background): “As shown in Fabrycky & Winn (2009), the true spin-orbit angle ψ, can be computed from β, ip (the orbital inclination), and i?”
• GIANT PLANETS ORBITING METAL-RICH STARS SHOW SIGNATURES OF PLANET–PLANET INTERACTIONS (2013, background): “Another orbital feature — the bimodal distribution of spin-orbit alignments among hot Jupiters — is sometimes interpreted as evidence for two migration mechanisms (Fabrycky & Winn 2009; Morton & Johnson 2011; Naoz et al. 2012).”
• SECULAR CHAOS AND THE PRODUCTION OF HOT JUPITERS (2010, methodology): “Analysis of the first 11 systems with R-M measurements found that the majority were consistent with perfect alignment, while a small minority were highly misaligned (Fabrycky & Winn 2009).”
• Homogeneous studies of transiting extrasolar planets - III. Additional planets and stellar models (2010, background): “Neglecting this population of massive planets (which may be a fundamentally different population to the lower mass ones; Fabrycky & Winn 2009; Southworth et al. 2009c), the rank correlation test of Spearman (1904) returns a probability of 99.80% (3.1σ) that thePorb–gb correlation is real and 97.6%…”
• MULTIPLE-PLANET SCATTERING AND THE ORIGIN OF HOT JUPITERS (2011, methodology): “This distribution should then be projected to the observer plane, and compared with observed distributions of λ (e.g., Fabrycky & Winn 2009).”
• The coronal X-ray - age relation and its implications for the evaporation of exoplanets (2011, background): “If both disk based and non-disk based migration are important with some planets undergoing one and some the other (as suggested by e.g. Fabrycky & Winn 2009) then it would be expected that there would be two distributions inM2P /R 3 P – 〈a〉 −2 space.”
• HOT STARS WITH HOT JUPITERS HAVE HIGH OBLIQUITIES (2010, unknown): “Another implication would be that attempts to compare the ensemble results forλ and the predictions of migration theories, such as those of Fabrycky & Winn (2009) and Triaud et al. (2010), should consider only hot stars, because cool stars may have been affected by subsequent tidal evolution.”
• About 30% of Sun-like Stars Have Kepler-like Planetary Systems: A Study of Their Intrinsic Architecture (2018, methodology): “With this inclination dispersion σi,k, the planetary inclination with respect to the invariable plane is then modeled as a Fisher (1953) distribution (Fabrycky & Winn 2009; Tremaine & Dong 2012) P (i|κk) = κk sin i 2 sinhκk eκk cos i .”
• Transits and Occultations (2010, result): “In many cases the results are consistent with good alignment, with measurement precisions ranging from 1–20◦ (for a recent summary, see Fabrycky & Winn 2009).”
• STARSPOTS, SPIN–ORBIT MISALIGNMENT, AND ACTIVE LATITUDES IN THE HAT-P-11 EXOPLANETARY SYSTEM (2011, background): “…because they are fundamental geometric parameters, and because they bear clues about the formation, migration, and tidal evolution of closein planets (see, e.g., Queloz et al. 2000; Ohta et al. 2005; Winn et al. 2005, 2010a; Fabrycky & Winn 2009; Triaud et al. 2010; Morton & Johnson 2011).”
• EVIDENCE OF POSSIBLE SPIN–ORBIT MISALIGNMENT ALONG THE LINE OF SIGHT IN TRANSITING EXOPLANET SYSTEMS (2010, methodology): “I describe the geometry of transiting exoplanet systems according to the conventions of Fabrycky & Winn (2009) in Figure 1.”
• OBLIQUITIES OF HOT JUPITER HOST STARS: EVIDENCE FOR TIDAL INTERACTIONS AND PRIMORDIAL MISALIGNMENTS (2012, methodology): “For simplicity we have chosen to work with projected obliquities, rather than attempting any deprojection scheme (Fabrycky & Winn 2009; Morton & Johnson 2011).”