Browsing by Subject "planets and"

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Asteroseismic Determination Of Obliquities Of The Exoplanet Systems Kepler-50 And Kepler-65
(2013-04) Chaplin, W. J.; Sanchis-Ojeda, R.; Campante, T. L.; Handberg, R.; Stello, D.; Winn, Joshua N.; Basu, S.; Christensen-Dalsgaard, J.; Davies, G. R.; Metcalfe, T. S.; Buchhave, Lars A.; Fischer, Debra A.; Bedding, T. R.; Cochran, William D.; Elsworth, Y.; Gilliland, R. L.; Hekker, S.; Huber, Daniel; Isaacson, Howard; Karoff, C.; Kawaler, Steven D.; Kjeldsen, H.; Latham, D. W.; Lund, M. N.; Lundkvist, M.; Marcy, Geoffrey W.; Miglio, A.; Barclay, Thomas; Lissauer, J. J.; Cochran, William D.
Results on the obliquity of exoplanet host stars-the angle between the stellar spin axis and the planetary orbital axis-provide important diagnostic information for theories describing planetary formation. Here we present the first application of asteroseismology to the problem of stellar obliquity determination in systems with transiting planets and Sun-like host stars. We consider two systems observed by the NASA Kepler mission which have multiple transiting small (super-Earth sized) planets: the previously reported Kepler-50 and a new system, Kepler-65, whose planets we validate in this paper. Both stars show rich spectra of solar-like oscillations. From the asteroseismic analysis we find that each host has its rotation axis nearly perpendicular to the line of sight with the sines of the angles constrained at the 1 sigma level to lie above 0.97 and 0.91, respectively. We use statistical arguments to show that coplanar orbits are favored in both systems, and that the orientations of the planetary orbits and the stellar rotation axis are correlated.
Circumbinary Planet Formation In The Kepler-16 System. II. A Toy Model For In Situ Planet Formation Within A Debris Belt
(2014-07) Meschiari, Stefano; Meschiari, Stefano
Recent simulations have shown that the formation of planets in circumbinary configurations (such as those recently discovered by Kepler) is dramatically hindered at the planetesimal accretion stage. The combined action of the binary and the protoplanetary disk acts to raise impact velocities between kilometer-sized planetesimals beyond their destruction threshold, halting planet formation within at least 10 AU from the binary. It has been proposed that a primordial population of "large" planetesimals (100 km or more in size), as produced by turbulent concentration mechanisms, would be able to bypass this bottleneck; however, it is not clear whether these processes are viable in the highly perturbed circumbinary environments. We perform two-dimensional hydrodynamical and N-body simulations to show that kilometer-sized planetesimals and collisional debris can drift and be trapped in a belt close to the central binary. Within this belt, planetesimals could initially grow by accreting debris, ultimately becoming "indestructible" seeds that can accrete other planetesimals in situ despite the large impact speeds. We find that large, indestructible planetesimals can be formed close to the central binary within 10(5) yr, therefore showing that even a primordial population of "small" planetesimals can feasibly form a planet.
A Correlation Between The Eclipse Depths Of Kepler Gas Giant Candidates And The Metallicities Of Their Parent Stars
(2012-06) Dodson-Robinson, Sarah E.; Dodson-Robinson, Sarah E.
Previous studies of the interior structure of transiting exoplanets have shown that the heavy-element content of gas giants increases with host star metallicity. Since metal-poor planets are less dense and have larger radii than metal-rich planets of the same mass, one might expect that metal-poor stars host a higher proportion of gas giants with large radii than metal-rich stars. Here I present evidence for a negative correlation at the 2.3 sigma level between eclipse depth and stellar metallicity in the Kepler gas giant candidates. Based on Kendall's tau statistics, the probability that eclipse depth depends on star metallicity is 0.981. The correlation is consistent with planets orbiting low-metallicity stars being, on average, larger in comparison with their host stars than planets orbiting metal-rich stars. Furthermore, since metal-rich stars have smaller radii than metal-poor stars of the same mass and age, a uniform population of planets should show a rise in median eclipse depth with [M/H]. The fact that I find the opposite trend indicates that substantial changes in the gas giant interior structure must accompany increasing [M/H]. I investigate whether the known scarcity of giant planets orbiting low-mass stars could masquerade as an eclipse depth-metallicity correlation, given the degeneracy between metallicity and temperature for cool stars in the Kepler Input Catalog. While the eclipse depth-metallicity correlation is not yet on firm statistical footing and will require spectroscopic [Fe/H] measurements for validation, it is an intriguing window into how the interior structure of planets and even the planet formation mechanism may be changing with Galactic chemical evolution.
Measurement of the Nodal Precession of WASP-33 B via Doppler Tomography
(2015-09) Johnson, Marshall C.; Cochran, William D.; Cameron, Andrew Collier; Bayliss, Daniel; Johnson, Marshall C.; Cochran, William D.
We have analyzed new and archival time series spectra taken six years apart during transits of the hot Jupiter WASP-33 b, and spectroscopically resolved the line profile perturbation caused by the Rossiter-McLaughlin effect. The motion of this line profile perturbation is determined by the path of the planet across the stellar disk, which we show to have changed between the two epochs due to nodal precession of the planetary orbit. We measured rates of change of the impact parameter and the sky-projected spin-orbit misalignment of db/dt = -0.0228(-0.0018)(+0.0050) yr(-1) and d lambda/dt = -0 degrees.487(-0.076)(+0.089) yr(-1) respectively corresponding to a rate of nodal precession of d Omega/dt = 0 degrees.373(-0.083)(+0.031) yr(-1) This is only the second measurement of nodal precession for a confirmed exoplanet transiting a single star. Finally, we used the rate of precession to set limits on the stellar gravitational quadrupole moment of 0.0054 <= J(2) <= 0.035.
Multi-Epoch Observations Of Hd 69830: High-Resolution Spectroscopy And Limits To Variability
(2011-12) Beichman, Charles A.; Lisse, C. M.; Tanner, A. M.; Bryden, G.; Akeson, R. L.; Ciardi, David R.; Boden, Andrew F.; Dodson-Robinson, Sarah E.; Salyk, Colette; Wyatt, M. C.; Dodson-Robinson, Sarah E.; Salyk, Colette
The main-sequence solar-type star HD 69830 has an unusually large amount of dusty debris orbiting close to three planets found via the radial velocity technique. In order to explore the dynamical interaction between the dust and planets, we have performed multi-epoch photometry and spectroscopy of the system over several orbits of the outer dust. We find no evidence for changes in either the dust amount or its composition, with upper limits of 5%-7% (1 sigma per spectral element) on the variability of the dust spectrum over 1 year, 3.3% (1 sigma) on the broadband disk emission over 4 years, and 33% (1 sigma) on the broadband disk emission over 24 years. Detailed modeling of the spectrum of the emitting dust indicates that the dust is located outside of the orbits of the three planets and has a composition similar to main-belt, C-type asteroids in our solar system. Additionally, we find no evidence for a wide variety of gas species associated with the dust. Our new higher signal-to-noise spectra do not confirm our previously claimed detection of H(2)O ice leading to a firm conclusion that the debris can be associated with the break-up of one or more C-type asteroids formed in the dry, inner regions of the protoplanetary disk of the HD 69830 system. The modeling of the spectral energy distribution and high spatial resolution observations in the mid-infrared are consistent with a similar to 1 AU location for the emitting material.
The Neptune-Sized Circumbinary Planet Kepler-38B
(2012-10) Orosz, Jerome A.; Welsh, William F.; Carter, Joshua A.; Brugamyer, Erik; Buchhave, Lars A.; Cochran, William D.; Endl, Michael; Ford, Eric B.; MacQueen, Phillip; Short, Donald R.; Torres, Guillermo; Windmiller, Gur; Agol, Eric; Barclay, Thomas; Caldwell, Douglas A.; Clarke, Bruce D.; Doyle, Laurance R.; Fabrycky, Daniel C.; Geary, John C.; Haghighipour, Nader; Holman, Matthew J.; Ibrahim, Khadeejah A.; Jenkins, Jon M.; Kinemuchi, Karen; Li, Jie; Lissauer, Jack J.; Prsa, Andrej; Ragozzine, Darin; Shporer, Avi; Still, Martin; Wade, Richard A.; Brugamyer, Erik; Cochran, William D.; Endl, Michael; MacQueen, Phillip
We discuss the discovery and characterization of the circumbinary planet Kepler-38b. The stellar binary is single-lined, with a period of 18.8 days, and consists of a moderately evolved main-sequence star (M-A = 0.949+/-0.059 M-circle dot and R-A = 1.757+/-0.034 R-circle dot) paired with a low-mass star (M-B = 0.249+/-0.010 M-circle dot and R-B = 0.2724+/-0.0053 R-circle dot) in a mildly eccentric (e = 0.103) orbit. A total of eight transits due to a circumbinary planet crossing the primary star were identified in the Kepler light curve (using Kepler Quarters 1-11), from which a planetary period of 105.595+/-0.053 days can be established. A photometric dynamical model fit to the radial velocity curve and Kepler light curve yields a planetary radius of 4.35+/-0.11 R-circle plus, or equivalently 1.12+/-0.03 R-Nep. Since the planet is not sufficiently massive to observably alter the orbit of the binary from Keplerian motion, we can only place an upper limit on the mass of the planet of 122 M-circle dot(7.11 M-Nep or equivalently 0.384 M-Jup) at 95% confidence. This upper limit should decrease as more Kepler data become available.
Planet Formation in Circumbinary Configurations: Turbulence Inhibits Planetesimal Accretion
(2012-12) Meschiari, Stefano; Meschiari, Stefano
The existence of planets born in environments highly perturbed by a stellar companion represents a major challenge to the paradigm of planet Formation. In numerical simulations, the presence of a close binary companion stirs up the relative velocity between planetesimals, which is fundamental in determining the balance between accretion and erosion. However, the recent discovery of circumbinary planets by Kepler establishes that planet Formation in binary systems is clearly viable. We perform N-body simulations of planetesimals embedded in a protoplanetary disk, where planetesimal phasing is frustrated by the presence of stochastic torques, modeling the expected perturbations of turbulence driven by the magnetorotational instability. We examine perturbation amplitudes relevant to dead zones in the midplane (conducive to planet Formation in single stars), and find that planetesimal accretion can be inhibited even in the outer disk (4-10 AU) far from the central binary, a location previously thought to be a plausible starting point for the Formation of circumbinary planets.
Transit Timing Observations From Kepler. II. Confirmation Of Two Multiplanet Systems Via A Non-Parametric Correlation Analysis
(2012-05) Ford, Eric B.; Fabrycky, Daniel C.; Steffen, Jason H.; Carter, Joshua A.; Fressin, Francois; Holman, Matthew J.; Lissauer, Jack J.; Moorhead, Althea V.; Morehead, Robert C.; Ragozzine, Darin; Rowe, Jason F.; Welsh, William F.; Allen, Christopher; Batalha, Natalie M.; Borucki, William J.; Bryson, Stephen T.; Buchhave, Lars A.; Burke, Christopher J.; Caldwell, Douglas A.; Charbonneau, David; Clarke, Bruce D.; Cochran, William D.; Desert, Jean-Michel; Endl, Michael; Everett, Mark E.; Fischer, Debra A.; Gautier, Thomas N, III; Gilliland, Ron L.; Jenkins, Jon M.; Haas, Michael R.; Horch, Elliott; Howell, Steve B.; Ibrahim, Khadeejah A; Isaacson, Howard; Koch, David G; Latham, David W; Li, Jie; Lucas, Philip; MacQueen, Phillip J; Marcy, Geoffrey W; McCauliff, Sean; Mullally, Fergal R; Quinn, Samuel N; Quintana, Elisa; Shporer, Avi; Still, Martin; Tenenbaum, Peter; Thompson, Susan E; Torres, Guillermo; Twicken, Joseph D; Wohler, Bill; Kepler Sci, Team; Cochran, William D.; Endl, Michael; MacQueen, Phillip J.
We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies is in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the TTVs of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple-planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.
Variability in A Young, L/T Transition Planetary-Mass Object
(2015-11) Biller, Beth A.; Vos, Johanna; Bonavita, Mariangela; Buenzli, Esther; Baxter, Claire; Crossfield, Ian J. M.; Allers, Katelyn; Liu, Michael C.; Bonnefoy, Mickael; Deacon, Niall; Brandner, Wolfgang; Schlieder, Joshua E.; Dupuy, Trent; Kopytova, Taisiya; Manjavacas, Elena; Allard, France; Homeier, Derek; Henning, Thomas; Dupuy, Trent
As part of our ongoing NTT SoFI survey for variability in young free-floating planets and low-mass brown dwarfs, we detect significant variability in the young, free-floating planetary-mass object PSO J318.5-22, likely due to rotational modulation of inhomogeneous cloud cover. A member of the 23 +/- 3 Myr beta Pic moving group, PSO J318.5-22 has T-eff = 1160(-40)(+30) K and a mass estimate of 8.3 +/- 0.5 M-Jup for a 23 +/- 3 Myr age. PSO J318.5-22 is intermediate in mass between 51 Eri b and beta Pic b, the two known exoplanet companions in the beta Pic moving group. With variability amplitudes from 7% to 10% in J(S) at two separate epochs over 3-5 hr observations, we constrain the rotational period of this object to >5 hr. In K-S, we marginally detect a variability trend of up to 3% over a 3 hr observation. This is the first detection of weather on an extrasolar planetary-mass object. Among L dwarfs surveyed at high photometric precision (<3%), this is the highest amplitude variability detection. Given the low surface gravity of this object, the high amplitude preliminarily suggests that such objects may be more variable than their high-mass counterparts, although observations of a larger sample are necessary to confirm this. Measuring similar variability for directly imaged planetary companions is possible with instruments such as SPHERE and GPI and will provide important constraints on Formation. Measuring variability at multiple wavelengths can help constrain cloud structure.