Peter De Cat

Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis

Significance The Kepler satellite has made revolutionary discoveries of thousands of planets down to Earth size. However, the orbital shapes (parameterized by eccentricities) of most Kepler planets remain unknown. We derive the eccentricity distributions of an unprecedented large and homogeneous sample of 698 Kepler planets. We discover a dichotomy in eccentricities: the systems with single transiting planets, which make up half of the sample, have a large mean eccentricity (∼ 0.3), whereas the multiples are on nearly circular orbits. The average eccentricity and inclination of the Kepler multiples and the solar system objects fit into an intriguing common pattern. Our results suggest that the circular and coplanar planetary orbits like those in our solar system are likely typical in the galaxy. The nearly circular (mean eccentricity e¯≈0.06) and coplanar (mean mutual inclination i¯≈3°) orbits of the solar system planets motivated Kant and Laplace to hypothesize that planets are formed in disks, which has developed into the widely accepted theory of planet formation. The first several hundred extrasolar planets (mostly Jovian) discovered using the radial velocity (RV) technique are commonly on eccentric orbits (e¯≈0.3). This raises a fundamental question: Are the solar system and its formation special? The Kepler mission has found thousands of transiting planets dominated by sub-Neptunes, but most of their orbital eccentricities remain unknown. By using the precise spectroscopic host star parameters from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) observations, we measure the eccentricity distributions for a large (698) and homogeneous Kepler planet sample with transit duration statistics. Nearly half of the planets are in systems with single transiting planets (singles), whereas the other half are multiple transiting planets (multiples). We find an eccentricity dichotomy: on average, Kepler singles are on eccentric orbits with e¯≈ 0.3, whereas the multiples are on nearly circular (e¯=0.04−0.04+0.03) and coplanar (i¯=1.4−1.1+0.8 degree) orbits similar to those of the solar system planets. Our results are consistent with previous studies of smaller samples and individual systems. We also show that Kepler multiples and solar system objects follow a common relation [e¯≈(1–2)×i¯] between mean eccentricities and mutual inclinations. The prevalence of circular orbits and the common relation may imply that the solar system is not so atypical in the galaxy after all.

Observational evidence for enhanced magnetic activity of superflare stars

Superflares are large explosive events on stellar surfaces one to six orders-of-magnitude larger than the largest flares observed on the Sun throughout the space age. Due to the huge amount of energy released in these superflares, it has been speculated if the underlying mechanism is the same as for solar flares, which are caused by magnetic reconnection in the solar corona. Here, we analyse observations made with the LAMOST telescope of 5,648 solar-like stars, including 48 superflare stars. These observations show that superflare stars are generally characterized by larger chromospheric emissions than other stars, including the Sun. However, superflare stars with activity levels lower than, or comparable to, the Sun do exist, suggesting that solar flares and superflares most likely share the same origin. The very large ensemble of solar-like stars included in this study enables detailed and robust estimates of the relation between chromospheric activity and the occurrence of superflares.

LAMOST Observations in the Kepler Field. Analysis of the Stellar Parameters Measured with LASP Based on Low-resolution Spectra

All of the 14 subfields of the Kepler field have been observed at least once with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, Xinglong Observatory, China) during the 2012-2014 observation seasons. There are 88,628 reduced spectra with SNR

LAMOST observations in the Kepler field

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LAMOST Observations in the Kepler Field. II. Database of the Low-resolution Spectra from the Five-year Regular Survey

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Synergies between spectroscopic and asteroseismic surveys for the Kepler field with LAMOST

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The Kepler field of view covered with the LAMOST spectroscopic observations

6 after the first round (2012-2014) of observations for the LAMOST-Kepler project (LK-project). By adopting the upgraded version of the LAMOST Stellar Parameter pipeline (LASP), we have determined the atmospheric parameters (

Asteroseismic observations of OB stars

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Joint Discussion 17 Highlights of recent progress in the seismology of the Sun and Sun-like stars

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Kepler Asteroseismology Program: Introduction and First Results

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