A Preponderance of Perpendicular Planets

Albrecht, Simon H.; Marcussen, Marcus L.; Winn, Joshua N.; Dawson, Rebekah I.; Knudstrup, Emil

doi:10.48550/arxiv.2105.09327

Cited by 8 publications

(11 citation statements)

References 59 publications

(61 reference statements)

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“…We note that we consider HD 3167b as aligned following the limit of Ψ "30 ˝commonly used in the exoplanet literature (e.g., Triaud et al 2010;Albrecht et al 2012). Albrecht et al (2021) recently confirmed that exoplanet systems do not span the full range of obliquities, but show a preference for nearly-perpendicular ("misaligned"; Ψ = 80-125 ˝) or low-obliquity ("aligned"; Ψ ă " 35 ˝) orbits. deg It is interesting to compare HD 3167 with other multiplanet systems with known architectures.…”

Section: Orbital Architecture Of the Hd 3167 System In Contextsupporting

confidence: 56%

The Rossiter-McLaughlin effect Revolutions: An ultra-short period planet and a warm mini-Neptune on perpendicular orbits

Bourrier,

Lovis,

Cretignier

et al. 2021

Preprint

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Comparisons of the alignment of exoplanets with a common host star and each other can be used to distinguish among concurrent evolution scenarios for the star and the planets. However, multi-planet systems usually host mini-Neptunes and super-Earths, whose sizes make orbital architecture measurements challenging. We introduce the Rossiter-McLaughlin effect Revolutions (RMR) technique, which can access the spin-orbit angle of small exoplanets by exploiting the full extent of information contained in spectral transit time series. We validated the technique through its application to published HARPS-N data of the mini-Neptune HD 3167c (P = 29.8 d), refining its high sky-projected spin-orbit angle (-108.9 `5.4 ´5.5 ˝), and we applied it to new ESPRESSO observations of the super-Earth HD 3167 b (P = 0.96 d), revealing an aligned orbit (-6.6 `6.6 ´7.9 ˝). Surprisingly different variations in the contrast of the stellar lines occulted by the two planets can be reconciled by assuming a latitudinal dependence of the stellar line shape. In this scenario, a joint fit to both datasets constrains the inclination of the star (111.6 `3.1 ´3.3 ˝) and the 3D spin-orbit angles of HD 3167b (29.5 `7.2 ´9.4 ˝) and HD 3167c (107.7 `5.1 ´4.9 ˝). The projected spin-orbit angles do not depend on the model for the line contrast variations, and so, with a mutual inclination of 102.3 `7.4 ´8.0 ˝, we can conclude that the two planets are on perpendicular orbits. This could be explained by HD 3167b being strongly coupled to the star and retaining its primordial alignment, whereas HD 3167c would have been brought to a nearly polar orbit via secular gravitational interactions with an outer companion. Followup observations of the system and simulations of its dynamical evolution are required to search for this companion and explore the likelihood of this scenario. HD 3167 b (R = 1.7 R Earth ) is the smallest exoplanet with a confirmed spectroscopic Rossiter-McLaughlin signal. The RMR technique opens the way to determining the orbital architectures of the super-Earth and Earth-sized planet populations.

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Section: Orbital Architecture Of the Hd 3167 System In Contextsupporting

confidence: 56%

The Rossiter-McLaughlin effect Revolutions: An ultra-short period planet and a warm mini-Neptune on perpendicular orbits

Bourrier,

Lovis,

Cretignier

et al. 2021

Preprint

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“…The slower action of equilibrium tides is required to push the star into a prograde state. Qualitatively, this sounds like a possible explanation for the observed overabundance of polar systems (Albrecht et al 2021), but in our simulations the currently-retrograde systems are tidally decoupled. This suggests that their polar configurations are a result of formation, rather than tidal evolution.…”

Section: Discussionmentioning

confidence: 50%

“…Indeed, none of the retrograde systems showed any significant movement towards a polar configuration, indicating that all retrograde systems are tidally decoupled over gigayear timescales. This implies that the observed overabundance of nearly-polar systems (Albrecht et al 2021) cannot be attributed to tidal evolution according to our model. Rather, this overabundance (if it is confirmed with future observations) may have been caused by the obliquity excitation mechanism.…”

Section: Observed Systemsmentioning

confidence: 64%

“…However, a large number of hot stars host hot Jupiters following retrograde orbits (Winn et al 2010;Albrecht et al 2012). Indeed, recent work has suggested that a preponderance of oblique hot stars lie close to, but slightly in excess of, 90 • of obliquity (Albrecht et al 2021). How do these "upside-down" systems fit into the picture?…”

Section: Model Systems: Retrogradementioning

confidence: 99%

“…Among stars hosting hot Jupiters, those with effective temperatures hotter than about 6100 K exhibit a broad range of obliquities; the angle between the sky projections of the spin and orbital axes spans the full range from 0 • to 180 • (Albrecht et al 2012), and the true obliquity ranges up to about 120 • (Albrecht et al 2021). In contrast, cooler stars typically have obliquities lower than 30 • whenever the planet's orbit is smaller than about 8 stellar radii (Winn et al 2010;Albrecht et al 2012;Winn & Fabrycky 2015;Winn et al 2017;Louden et al 2021).…”

Section: Introductionmentioning

confidence: 99%

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Tidal erasure of stellar obliquities constrains the timing of hot Jupiter formation

Spalding,

Winn

2022

Preprint

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Stars with hot Jupiters sometimes have high obliquities, which are possible relics of hot Jupiter formation. Based on the characteristics of systems with and without high obliquities, it is suspected that obliquities are tidally damped when the star has a thick convective envelope, as is the case for main-sequence stars cooler than ∼6100K, and the orbit is within ∼8 stellar radii. A promising theory for tidal obliquity damping is the dissipation of inertial waves within the star's convective envelope. Here, we consider the implications of this theory for the timing of hot Jupiter formation. Specifically, hot stars that currently lack a convective envelope possess one during their pre-main sequence. We find that hot Jupiters orbiting within a critical distance of ∼0.02 au from a misaligned main-sequence star lacking a thick convective envelope must have acquired their tight orbits after a few tens of millions of years in order to have retained their obliquities throughout the pre-main-sequence. There are 4 known systems for which this argument applies-XO-3b, Corot-3b, WASP-14b, and WASP-121b-subject to uncertainties surrounding inertial wave dissipation. Moreover, we conclude that a recently-identified overabundance of near-polar hot Jupiters is unlikely sculpted by tides, instead reflecting their primordial configuration. Finally, hot Jupiters arriving around cool stars after a few 100s of millions of years likely find the host star rotating too slowly for efficient obliquity damping. We predict that the critical effective temperature separating aligned and misaligned stars should vary with metallicity, from 6300 K to 6000 K as [Fe/H] varies from −0.3 to +0.3.

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The flipped orbit of KELT-19Ab inferred from the symmetric TESS transit light curves

Kawai,

Narita,

Fukui

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Dozens of planets are now discovered with large orbital obliquity, and have become the proof for the dynamical evolution of planetary orbits. In the current samples, there is an apparent clustering of planets around 90○, and also an absence of planets around 180○ although the latter is expected by some theories. Statistical extrapolation using Hierarchical Bayesian Analysis have recently refuted the significant clustering around 90○ and suggested that the distribution may actually be broader. In this work, the symmetric TESS transit light curve of KELT-19Ab is analyzed using gravity darkening to measure its true obliquity. Its large sky projected obliquity $\lambda = -179.7^{\circ +3.7^\circ }_{\, \, -3.8^\circ }$ makes KELT-19Ab the only currently known planet with obliquity potentially close to 180○. We apply spectroscopic constraints on vsini and λ as well as theoretical constraints on the limb-darkening coefficients to find that the KELT-19Ab’s obliquity is $\psi = 155^{\circ +17^\circ }_{\, \, -21^\circ }$, in favor of a flipped orbit. The result is consistent with the statistically inferred uniformity of obliquity distribution, and also highlights the applicability of the gravity darkening technique to symmetric light curves.

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A Preponderance of Perpendicular Planets

Cited by 8 publications

References 59 publications

The Rossiter-McLaughlin effect Revolutions: An ultra-short period planet and a warm mini-Neptune on perpendicular orbits

The Rossiter-McLaughlin effect Revolutions: An ultra-short period planet and a warm mini-Neptune on perpendicular orbits

Tidal erasure of stellar obliquities constrains the timing of hot Jupiter formation

The flipped orbit of KELT-19Ab inferred from the symmetric TESS transit light curves

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