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Posts: 131433
Date:
Kepler-19
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Title: The Kepler-19 system: a thick-envelope super-Earth with two Neptune-mass companions characterized using Radial Velocities and Transit Timing Variations
Author: Luca Malavolta, Luca Borsato, Valentina Granata, Giampaolo Piotto, Eric Lopez, Andrew Vanderburg, Pedro Figueira, Annelies Mortier, Valerio Nascimbeni, Laura Affer, Aldo S. Bonomo, Francois Bouchy, Lars A. Buchhave, David Charbonneau, Andrew Collier Cameron, Rosario Cosentino, Courtney D. Dressing, Xavier Dumusque, Aldo F. M. Fiorenzano, Avet Harutyunyan, Raphaëlle D. Haywood, John Asher Johnson, David W. Latham, Mercedes Lopez-Morales, Christophe Lovis, Michel Mayor, Giusi Micela, Emilio Molinari, Fatemeh Motalebi, Francesco Pepe, David F. Phillips, Don Pollacco, Didier Queloz, Ken Rice, Dimitar Sasselov, Damien Ségransan, Alessandro Sozzetti, Stéphane Udry, Chris Watson

We report a detailed characterization of the Kepler-19 system. This star was previously known to host a transiting planet with a period of 9.29 days, a radius of 2.2 earth radii and an upper limit on the mass of 20 earth masses. The presence of a second, non-transiting planet was inferred from the transit time variations (TTVs) of Kepler-19b, over 8 quarters of Kepler photometry, although neither mass nor period could be determined. By combining new TTVs measurements from all the Kepler quarters and 91 high-precision radial velocities obtained with the HARPS-N spectrograph, we measured through dynamical simulations a mass of 8.4±1.6 earth masses for Kepler-19b. From the same data, assuming system coplanarity, we determined an orbital period of 28.7 days and a mass of 13.1±2.7 earth masses for Kepler-19c and discovered a Neptune-like planet with a mass of 20.3±3.4 earth masses on a 63 days orbit. By comparing dynamical simulations with non-interacting Keplerian orbits, we concluded that neglecting interactions between planets may lead to systematic errors that could hamper the precision in the orbital parameters when the dataset spans several years. With a density of 4.32±0.87 g cm^-3 (0.78±0.16 earth density) Kepler-19b belongs to the group of planets with a rocky core and a significant fraction of volatiles, in opposition to low-density planets characterized by transit-time variations only and the increasing number of rocky planets with Earth-like density. Kepler-19 joins the small number of systems that reconcile transit timing variation and radial velocity measurements.

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Posts: 131433
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RE: Kepler-19c
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Transit planet search reveals doubly-tilted solar system

Some 650 light years away, Kepler 19 possesses one world, Kepler 19b, revealed by NASA's Kepler space telescope. The space telescope unblinkingly looks at more than 100,000 stars out to roughly 3,000 light years from Earth (one light year is about 5.9 trillion miles), looking for dips in starlight caused by "transits" of planets orbiting around them. Kepler 19b orbits its star once about every 9 days and appears twice as big as Earth, making it a "mini-Neptune" class planet.
However the planet's orbit possesses one oddity, a five-minute glitch in the timing of its transit's repetition that suggests a companion world must be slowing it down. The companion, Kepler 19c, doesn't turn up in the transit survey, suggesting it must orbit on a different inclination than the first planet.

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Posts: 131433
Date:
Kepler-19 System
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Title: The Kepler-19 System: A Transiting 2.2 R_Earth Planet and a Second Planet Detected via Transit Timing Variations
Authors: Sarah Ballard, Daniel Fabrycky, Francois Fressin, David Charbonneau, Jean-Michel Desert, Guillermo Torres, Geoffrey Marcy, Christopher J. Burke, Howard Isaacson, Christopher Henze, Jason H. Steffen, David R. Ciardi, Steven B. Howell, William D. Cochran, Michael Endl, Stephen T. Bryson, Jason F. Rowe, Matthew J. Holman, Jack J. Lissauer, Jon M. Jenkins, Martin Still, Eric B. Ford, Jessie L. Christiansen, Christopher K. Middour, Michael R. Haas, Jie Li, Jennifer R. Hall, Sean McCauliff, Natalie M. Batalha, David G. Koch, William J. Borucki

We present the discovery of the Kepler-19 planetary system, which we first identified from a 9.3-day periodic transit signal in the Kepler photometry. From high-resolution spectroscopy of the star, we find a stellar effective temperature Teff=5541 ±60 K, a metallicity [Fe/H]=-0.13 ±0.06, and a surface gravity log(g)=4.59 ±0.10. We combine the estimate of Teff and [Fe/H] with an estimate of the stellar density derived from the photometric light curve to deduce a stellar mass of M_star = 0.936 ±0.040 M_Sun and a stellar radius of R_star = 0.850 ±0.018 R_Sun. We rule out the possibility that the transits result from an astrophysical false positive by first identifying the subset of stellar blends that reproduce the precise shape of the light curve. We conclude that the planetary scenario is more than three orders of magnitude more likely than a blend. The blend scenario is independently disfavoured by the achromaticity of the transit: we measure a transit depth with Spitzer at 4.5 {\mu}m of 547+113-110 ppm, consistent with the depth measured in the Kepler optical bandpass of 567 ±6 ppm. We determine a physical radius of the planet Kepler-19b of R_p = 2.209 ±0.048 R_Earth. From radial-velocity observations of the star, we find an upper limit on the planet mass of 20.3 M_Earth, corresponding to a maximum density of 10.4 g cm^-3. We report a significant sinusoidal deviation of the transit times from a predicted linear ephemeris, which we conclude is due to an additional perturbing body in the system. We cannot uniquely determine the orbital parameters of the perturber, as various dynamical mechanisms match the amplitude, period, and shape of the transit timing signal and satisfy the host star's radial velocity limits. However, the perturber in these mechanisms has period <160 days and mass <6 M_Jup, confirming its planetary nature as Kepler-19c.

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Posts: 131433
Date:
RE: Kepler-19b
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Invisible World Discovered

The first planet, Kepler-19b, transits its star every 9 days and 7 hours. It orbits the star at a distance of 8.4 million miles, where it is heated to a temperature of about 900 degrees Fahrenheit. Kepler-19b has a diameter of 18,000 miles, making it slightly more than twice the size of Earth.
If Kepler-19b were alone, each transit would follow the next like clockwork. Instead, the transits come up to five minutes early or five minutes late. Such transit timing variations show that another world's gravity is pulling on Kepler-19b, alternately speeding it up or slowing it down.

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Posts: 131433
Date:
Kepler-19c
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Invisible World Discovered

Usually, running five minutes late is a bad thing since you might lose your dinner reservation or miss out on tickets to the latest show. But when a planet runs five minutes late, astronomers get excited because it suggests that another world is nearby.
NASA's Kepler spacecraft has spotted a planet that alternately runs late and early in its orbit because a second, "invisible" world is tugging on it. This is the first definite detection of a previously unknown planet using this method. No other technique could have found the unseen companion.

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