Spin-orbit alignment of exoplanet systems: analysis of an ensemble of asteroseismic observations

AbstractMeasuring the obliquities of exoplanet-host stars provides invaluable diagnostic information for theories of planetary formation and migration. Most of these results have so far been obtained by measuring the Rossiter–McLaughlin effect, clearly favoring systems that harbor hot Jupiters. While it would be extremely helpful to extend these measurements to long-period and multiple-planet systems, it is also true that the latter systems tend to involve smaller planets, making it ever so difficult to apply such techniques. Asteroseismology provides a powerful method of determining the inclination of the stellar spin axis — from an analysis of the rotationally-induced splittings of the oscillation modes — whose applicability is ultimately determined by the stellar parameters and not by the signal-to-noise ratio of the transit data. Here we present the first statistical analysis of an ensemble of asteroseismic obliquity measurements obtained for solar-type stars with transiting planets. The sample consists of 25 Kepler planet-candidate host stars, 14 of which are multi-transiting systems. We seek empirical constraints on the spin-orbit alignment of exoplanet systems and discuss the implications for theories of planetary formation and migration.

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Spin-orbit alignment of exoplanet systems: how can Asteroseismology help us?

Proceedings of the International Astronomical Union ◽

10.1017/s1743921316002428 ◽

2015 ◽

Vol 11 (A29A) ◽

pp. 71-76

Author(s):

Tiago L. Campante

Keyword(s):

Signal To Noise Ratio ◽

Spin Orbit ◽

Hot Jupiters ◽

Long Period ◽

Oscillation Modes ◽

And Migration ◽

Stellar Properties ◽

Orbit Geometry ◽

Exoplanet Systems ◽

Host Stars

AbstractMeasuring the obliquities of exoplanet-host stars provides invaluable diagnostic information for theories of planetary formation and migration. Most of these results have so far been obtained by measuring the Rossiter--McLaughlin effect, clearly favoring systems that harbor hot Jupiters. While it would be extremely helpful to extend these measurements to long-period and multiple-planet systems, it is also true that the latter systems tend to involve smaller planets, making it ever so difficult to apply such techniques. Asteroseismology provides a powerful method of determining the inclination of the stellar spin axis from an analysis of the rotationally-induced splittings of the oscillation modes. This provides an estimate of the obliquity independently of other methods. The applicability of the asteroseismic method is determined by the stellar properties and not by the signal-to-noise ratio of the transit data. Here we present a recap of the spin-orbit geometry, explain how the asteroseismic method works, and review previous applications of the method to exoplanet-host stars.

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A search for transiting planets in the β Pictoris system

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731941 ◽

2018 ◽

Vol 615 ◽

pp. A145 ◽

Cited By ~ 3

Author(s):

M. Mol Lous ◽

E. Weenk ◽

M. A. Kenworthy ◽

K. Zwintz ◽

R. Kuschnig

Keyword(s):

Signal To Noise Ratio ◽

Large Fraction ◽

Young Star ◽

High Signal ◽

Data Set ◽

Transiting Planets ◽

Using Data ◽

Exoplanet Systems ◽

Transit Signals

Context. Transiting exoplanets provide an opportunity for the characterization of their atmospheres, and finding the brightest star in the sky with a transiting planet enables high signal-to-noise ratio observations. The Kepler satellite has detected over 365 multiple transiting exoplanet systems, a large fraction of which have nearly coplanar orbits. If one planet is seen to transit the star, then it is likely that other planets in the system will transit the star too. The bright (V = 3.86) star β Pictoris is a nearby young star with a debris disk and gas giant exoplanet, β Pictoris b, in a multi-decade orbit around it. Both the planet’s orbit and disk are almost edge-on to our line of sight. Aims. We carry out a search for any transiting planets in the β Pictoris system with orbits of less than 30 days that are coplanar with the planet β Pictoris b. Methods. We search for a planetary transit using data from the BRITE-Constellation nanosatellite BRITE-Heweliusz, analyzing the photometry using the Box-Fitting Least Squares Algorithm (BLS). The sensitivity of the method is verified by injection of artificial planetary transit signals using the Bad-Ass Transit Model cAlculatioN (BATMAN) code. Results. No planet was found in the BRITE-Constellation data set. We rule out planets larger than 0.6 RJ for periods of less than 5 days, larger than 0.75 RJ for periods of less than 10 days, and larger than 1.05 RJ for periods of less than 20 days.

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The Rossiter-McLaughlin effect for exoplanets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311020230 ◽

2010 ◽

Vol 6 (S276) ◽

pp. 230-237

Author(s):

Joshua N. Winn

Keyword(s):

Measurement Technique ◽

Planet Formation ◽

Hot Jupiters ◽

Transiting Planets ◽

History Of ◽

And Migration

AbstractThere are now more than 35 stars with transiting planets for which the stellar obliquity—or more precisely its sky projection—has been measured, via the eponymous effect of Rossiter and McLaughlin. The history of these measurements is intriguing. For 8 years a case was gradually building that the orbits of hot Jupiters are always well-aligned with the rotation of their parent stars. Then in a sudden reversal, many misaligned systems were found, and it now seems that even retrograde systems are not uncommon. I review the measurement technique underlying these discoveries, the patterns that have emerged from the data, and the implications for theories of planet formation and migration.

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Searching for debris discs in the 30 Myr open cluster IC 4665

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038205 ◽

2020 ◽

Vol 641 ◽

pp. A156

Author(s):

N. Miret-Roig ◽

N. Huélamo ◽

H. Bouy

Keyword(s):

Open Cluster ◽

Spectral Energy Distribution ◽

Young Stars ◽

Spectral Energy ◽

Virtual Observatory ◽

Planetary Formation ◽

Infrared Excess ◽

Solar Type ◽

Dust Evolution ◽

Host Stars

Context. Debris discs orbiting young stars are key to understanding dust evolution and the planetary formation process. We take advantage of a recent membership analysis of the 30 Myr nearby open cluster IC 4665 based on the Gaia and DANCe surveys to revisit the disc population of this cluster. Aims. We aim to study the disc population of IC 4665 using Spitzer (MIPS and IRAC) and WISE photometry. Methods. We use several colour–colour diagrams with empirical photospheric sequences to detect the sources with an infrared excess. Independently, we also fit the spectral energy distribution (SED) of our debris-disc candidates with the Virtual Observatory SED analyser (VOSA) which is capable of automatically detecting infrared excesses and provides effective temperature estimates. Results. We find six candidate debris-disc host stars (five with MIPS and one with WISE), two of which are new candidates. We estimate a disc fraction of 24 ± 10% for the B–A stars, where our sample is expected to be complete. This is similar to what has been reported in other clusters of similar ages (Upper Centaurus Lupus, Lower Centaurus Crux, the β Pictoris moving group, and the Pleiades). For solar-type stars we find a disc fraction of 9 ± 9%, which is lower than that observed in regions with comparable ages. Conclusions. Our candidate debris-disc host stars are excellent targets to be studied with ALMA or the future James Webb Space Telescope (JWST).

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A multiplicity study of transiting exoplanet host stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937334 ◽

2020 ◽

Vol 635 ◽

pp. A74 ◽

Cited By ~ 3

Author(s):

J. Southworth ◽

A. J. Bohn ◽

M. A. Kenworthy ◽

C. Ginski ◽

L. Mancini

Keyword(s):

Physical Properties ◽

Extrasolar Planets ◽

Population Level ◽

Light Curves ◽

Nearby Star ◽

Hot Jupiters ◽

Nearby Stars ◽

Solar Type ◽

Widespread Phenomenon ◽

Host Stars

Context. Binarity is a widespread phenomenon around solar-type stars, including the host stars of transiting extrasolar planets. Aims. We performed a detailed study of six transiting planetary systems with relatively bright stars close enough to affect observations of these systems. These contaminants were characterised in a companion work. Methods. We used theoretical spectra to propagate the observed K-band light ratios into the optical passbands used to observe these systems. Light curves were analysed whilst taking the contaminating light and its uncertainty into account. We present and applied a method to correct the velocity amplitudes of the host stars for the presence of contaminating light. Results. We determined the physical properties of six systems (WASP-20, WASP-70, WASP-8, WASP-76, WASP-2, and WASP-131) whilst accounting for contaminating light. In the case of WASP-20, the measured physical properties are very different for the three scenarios considered: ignoring binarity, planet transits brighter star, and planet transits fainter star. In the other five cases, our results are very similar to those obtained when neglecting contaminating light. We used our results to determine the mean correction factors to planet radius, ⟨XR⟩, mass, ⟨XM⟩, and density, ⟨Xρ⟩, caused by nearby objects. We find ⟨XR⟩ = 1.009 ± 0.045, which is smaller than literature values because we were able to reject the possibility that the planet orbits the fainter star in all but one case. We find ⟨XM⟩ = 1.031 ± 0.019, which is larger than ⟨XR⟩ because of the strength of the effect of contaminating light on the radial velocity measurements of the host star. We find ⟨Xρ⟩ = 0.995 ± 0.046: the small size of this correction is due to two effects: the corrections on planet radius and mass partially cancel; and some nearby stars are close enough to contaminate the light curves of the system but not radial velocities of the host star. These corrections can be applied to samples of transiting hot Jupiters to statistically remove biases due to light contamination. Conclusions. We conclude that binarity of planet host stars is important for the small number of transiting hot Jupiters with a very bright and close nearby star, but it has only a small effect on population-level studies of these objects.

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LAMOST telescope reveals that Neptunian cousins of hot Jupiters are mostly single offspring of stars that are rich in heavy elements

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1711406115 ◽

2017 ◽

Vol 115 (2) ◽

pp. 266-271 ◽

Cited By ~ 35

Author(s):

Subo Dong ◽

Ji-Wei Xie ◽

Ji-Lin Zhou ◽

Zheng Zheng ◽

Ali Luo

Keyword(s):

Main Sequence ◽

The Other ◽

Heavy Elements ◽

Main Sequence Stars ◽

Hot Jupiters ◽

Transiting Planets ◽

Short Period ◽

Data Release ◽

Order Of Magnitude ◽

Solar Type

We discover a population of short-period, Neptune-size planets sharing key similarities with hot Jupiters: both populations are preferentially hosted by metal-rich stars, and both are preferentially found in Kepler systems with single-transiting planets. We use accurate Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 4 (DR4) stellar parameters for main-sequence stars to study the distributions of short-period (1d<P<10d)Kepler planets as a function of host star metallicity. The radius distribution of planets around metal-rich stars is more “puffed up” compared with that around metal-poor hosts. In two period–radius regimes, planets preferentially reside around metal-rich stars, while there are hardly any planets around metal-poor stars. One is the well-known hot Jupiters, and the other one is a population of Neptune-size planets (2R⊕≲Rp≲6R⊕), dubbed “Hoptunes.” Also like hot Jupiters, Hoptunes occur more frequently in systems with single-transiting planets although the fraction of Hoptunes occurring in multiples is larger than that of hot Jupiters. About 1% of solar-type stars host Hoptunes, and the frequencies of Hoptunes and hot Jupiters increase with consistent trends as a function of [Fe/H]. In the planet radius distribution, hot Jupiters and Hoptunes are separated by a “valley” at approximately Saturn size (in the range of 6R⊕≲Rp≲10R⊕), and this “hot-Saturn valley” represents approximately an order-of-magnitude decrease in planet frequency compared with hot Jupiters and Hoptunes. The empirical “kinship” between Hoptunes and hot Jupiters suggests likely common processes (migration and/or formation) responsible for their existence.

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Transmission spectroscopy and Rossiter-McLaughlin measurements of the young Neptune orbiting AU Mic

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038583 ◽

2020 ◽

Vol 643 ◽

pp. A25

Author(s):

E. Palle ◽

M. Oshagh ◽

N. Casasayas-Barris ◽

T. Hirano ◽

M. Stangret ◽

...

Keyword(s):

Time Series ◽

Signal To Noise Ratio ◽

Dynamical Evolution ◽

Spin Orbit ◽

Large Signal ◽

Atmospheric Transmission ◽

Transmission Spectroscopy ◽

Very Large Telescope ◽

Rotation Plane ◽

And Migration

AU Mic b is a Neptune-sized planet on an 8.47-day orbit around the nearest pre-main sequence (~20 Myr) star to the Sun, the bright (V = 8.81) M dwarf AU Mic. The planet was preliminary detected in Doppler radial velocity time series and recently confirmed to be transiting with data from the TESS mission. AU Mic b is likely to be cooling and contracting and might be accompanied by a second, more massive planet, in an outer orbit. Here, we present the observations of the transit of AU Mic b using ESPRESSO on the Very Large Telescope. We obtained a high-resolution time series of spectra to measure the Rossiter-McLaughlin effect, to constrain the spin-orbit alignment of the star and planet, and to simultaneously attempt to retrieve the planet’s atmospheric transmission spectrum. These observations allowed us to study, for the first time, the early phases of the dynamical evolution of young systems. We applied different methodologies to derive the spin-orbit angle of AU Mic b, and all of them retrieve values consistent with the planet being aligned with the rotation plane of the star. We determined a conservative spin-orbit angle λ value of −2.96−10.30+10.44 degrees, indicative that the formation and migration of the planets of the AU Mic system occurred within the disc. Unfortunately, and despite the large signal-to-noise ratio of our measurements, the degree of stellar activity prevented us from detecting any features from the planetary atmosphere. In fact, our results suggest that transmission spectroscopy for recently formed planets around active young stars is going to remain very challenging, if at all possible, for the near future.

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Dynamical masses of two infant giant planets

10.21203/rs.3.rs-484057/v1 ◽

2021 ◽

Author(s):

Alejandro Suárez Mascareño ◽

Mario Damasso ◽

Nicolas Lodieu ◽

Alessandro Sozzetti ◽

Víctor Béjar ◽

...

Keyword(s):

Solar System ◽

Orbital Period ◽

Giant Planets ◽

Final Size ◽

Stellar Activity ◽

Planetary Evolution ◽

Transiting Planets ◽

Solar Type ◽

Host Stars ◽

Dynamical Masses

Abstract Current theories of planetary evolution predict that infant giant planets have large radii and very low densities before they slowly contract to reach their final size after about several hundred million years 1, 2. These theoretical expectations remain untested to date, despite the increasing number of exoplanetary discoveries, as the detection and characterisation of very young planets is extremely challenging due to the intense stellar activity of their host stars 3, 4. However, the recent discoveries of young planetary transiting systems allow to place initial constraints on evolutionary models5–9. With an estimated age of 20 million years, V1298 Tau is one of the youngest solar-type stars known to host transiting planets: it harbours a multiple system composed of two Neptune-sized, one Saturn-sized, and one Jupiter-sized planets 10, 11. Here we report the dynamical masses of two of the four planets. We find that planet b, with an orbital period of 24 days, has a mass of 0.60 Jupiter masses and a density similar to the giant planets of the Solar System and other known giant exoplanets with significantly older ages 12, 13. Planet e, with an orbital period of 40 days, has a mass of 1.21 Jupiter masses and a density larger than most giant exoplanets. This is unexpected for planets at such a young age and suggests that some giant planets might evolve and contract faster than anticipated, thus challenging current models of planetary evolution.

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A multiplicity study of transiting exoplanet host stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937127 ◽

2020 ◽

Vol 635 ◽

pp. A73 ◽

Cited By ~ 3

Author(s):

A. J. Bohn ◽

J. Southworth ◽

C. Ginski ◽

M. A. Kenworthy ◽

P. F. L. Maxted ◽

...

Keyword(s):

Proper Motion ◽

Angular Separation ◽

Current Data ◽

Formation Mechanisms ◽

Multiple Systems ◽

Hot Jupiters ◽

Data Release ◽

And Migration ◽

Almost All ◽

Host Stars

Context. Many main-sequence stars are part of multiple systems. The effect of stellar multiplicity on planet formation and migration, however, is poorly understood. Aims. We study the multiplicity of stars hosting known transiting extra-solar planets to test competing theories on the formation mechanisms of hot Jupiters. Methods. We observed 45 exoplanet host stars using the infrared dual imaging spectrograph of the Spectro-Polarimetric High-Contrast Exoplanet Research (SPHERE) instrument at the Very Large Telescope to search for potential companions. For each identified candidate companion we determined the probability that it is gravitationally bound to its host by performing common proper motion checks and modelling of synthetic stellar populations around the host. In addition, we derived contrast limits as a function of angular separation to set upper limits on further companions in these systems. We converted the derived contrast into mass thresholds using AMES-Cond, AMES-Dusty, and BT-Settl models. Results. We detected new candidate companions around K2-38, WASP-72, WASP-80, WASP-87, WASP-88, WASP-108, WASP-118, WASP-120, WASP-122, WASP123, WASP-130, WASP-131, and WASP-137. The closest candidates were detected at separations of 0.′′124±0.′′007 and 0.′′189±0.′′003 around WASP-108 and WASP-131; the measured K-band contrasts indicate that these are stellar companions of 0.35 ± 0.02 M⊙ and 0.62−0.04+0.05 M⊙, respectively. Including the re-detection and confirmation of previously known companions in 13 other systems, we derived a multiplicity fraction of 55.4−9.4+5.9%. For the representative sub-sample of 40 hot Jupiter host stars among our targets, the derived multiplicity rate is 54.8−9.9+6.3%. Our data do not confirm any trend that systems with eccentric planetary companions are preferably part of multiple systems. On average, we reached a magnitude contrast of 8.5 ± 0.9 mag at an angular separation of 0.′′5. This allows us to exclude additional stellar companions with masses higher than 0.08M⊙ for almost all observed systems; around the closest and youngest systems, this sensitivity is achieved at physical separations as small as 10 au. Conclusions. Our study shows that SPHERE is an ideal instrument for detecting and characterising close companions to exoplanetary host stars. Although the second data release of the Gaia mission also provides useful constraints for some of the systems, the achieved sensitivity provided by the current data release of this mission is not good enough to measure parallaxes and proper motions for all detected candidates. For 14 identified companion candidates further astrometric epochs are required to confirm their common proper motion at 5σ significance.

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Kinematic interpretation in the prestack depth‐migrated domain

Geophysics ◽

10.1190/1.1444224 ◽

1997 ◽

Vol 62 (4) ◽

pp. 1226-1237 ◽

Cited By ~ 8

Author(s):

Irina Apostoiu‐Marin ◽

Andreas Ehinger

Keyword(s):

Signal To Noise Ratio ◽

Velocity Model ◽

Point Of View ◽

Prestack Depth Migration ◽

Depth Migration ◽

Velocity Models ◽

Time Domain Data ◽

And Migration ◽

Point To Point ◽

Homogeneous Media

Prestack depth migration can be used in the velocity model estimation process if one succeeds in interpreting depth events obtained with erroneous velocity models. The interpretational difficulty arises from the fact that migration with erroneous velocity does not yield the geologically correct reflector geometries and that individual migrated images suffer from poor signal‐to‐noise ratio. Moreover, migrated events may be of considerable complexity and thus hard to identify. In this paper, we examine the influence of wrong velocity models on the output of prestack depth migration in the case of straight reflector and point diffractor data in homogeneous media. To avoid obscuring migration results by artifacts (“smiles”), we use a geometrical technique for modeling and migration yielding a point‐to‐point map from time‐domain data to depth‐domain data. We discover that strong deformation of migrated events may occur even in situations of simple structures and small velocity errors. From a kinematical point of view, we compare the results of common‐shot and common‐offset migration. and we find that common‐offset migration with erroneous velocity models yields less severe image distortion than common‐shot migration. However, for any kind of migration, it is important to use the entire cube of migrated data to consistently interpret in the prestack depth‐migrated domain.

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