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2013-05-28T14:00
Exoplanets
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1400 |
Doyon, Rene |
Discovery of a planetary mass companion around a young low-mass star |
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We present the discovery a planetary-mass companion located 2000 AU from a M3 star, member of the young (50-120 Myr) AB Doradus moving group. It was identified through an ongoing survey with GMOS at Gemini-South, via its distinctively red i-z color (>3.5). The comoving status of this object was confirmed by 2 epochs of WIRCam/CFHT J-band images. The NIR photometry and WISE colors suggest an early-to-mid T bound companion. A NIR spectrum, taken with GNIRS at Gemini-North, confirms a mid-T spectral type. With an estimated temperature between 900K and 1200 K, models predict a mass between 7 and 12 MJup for this object. The benchmark character of this planetary mass object lies in its relatively well-constrained age and in its very wide separation, that allows in-depth studies that can help validating models and understanding similar but closer-in companions such as the ones that will be uncovered by forthcoming planet finder such as GPI and SPHERE. |
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1415 |
Dragomir, Diana |
New results from the MOST super-Earth transit search |
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We present results from our ongoing search for transits of radial velocity-detected super-Earth candidates using the MOST space telescope. The program aims to populate the area of exoplanet parameter space that encompasses these small exoplanets, and in particular to find such transiting super-Earths in orbit around bright stars. This aspect of the search is essential to facilitating follow-up studies of those systems. For 55 Cnc e, a super-Earth transiting a naked-eye star and the first positive detection of the transit search, we combine MOST photometry from 2011, 2012 and 2013 to improve the planetary parameters and search for phase variations and the planet's secondary eclipse. In addition, we also report new findings on our other transit search candidates. |
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1430 |
Van Laerhoven, Christa |
Tides Among Planets: In-fall, Damping, and Habitability |
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In a multi-planet system planets can share angular momentum, complicating how imposed orbital changes (e.g. eccentricity damping) actually manifest. Eccentricities are composed of a sum of several eigenmodes and thus can have a heterogeneous response as the eigenmodes' structure and amplitude change. I will elucidate this by showing time evolution due to various imposed changes using analytic expressions rooted in classical secular theory. In the case of tidal evolution, each eigenmode will damp at its own rate set by the structure of the system. In addition, that underlying structure will change as the inner planet's semi-major axis changes. As a result, the orbital evolution of a coupled multi-planet system is qualitatively different from that of a single-planet system. This has several implications: The lifetimes of inner planets are shortened compared to that of their single brethren; Planets that are too far from their star to experience direct tidal evolution can have their obits significantly changed via secular interaction with a tidally evolving inner companion; Planets in the (insolation) habitable zones of low mass stars can have tidal heating histories that would make life difficult. Thus, when considering the orbital evolution of a planet it is very important to include the effects of its companions. |
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1445 |
Esteves, Lisa |
Kepler Phasecurves: Pushing the Limits of Kepler's Photometric Precision |
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Kepler photometry is primarily used to measure the change in brightness, of a star, during a planetary transit. However, there is a lot more to be learned from the out-of-transit light-curve variations, otherwise known as the phasecurve. It's only recently, with the use of over 4 years of Kepler data, that we've been able to get down to the precision needed to measure these variations. I present results of a recently submitted paper, describing the observations of 8 Kepler phasecurves including 5 new phasecurves and re-examining 3 previously published results. |
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1500 |
Huber, Daniel |
Asteroseismology of Kepler Exoplanet Host Stars |
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The measurement of stellar oscillations is among the most powerful observational tools to determine fundamental properties of stars. The high precision photometry by the Kepler space telescope has enabled for the first time to systematically detect stellar oscillations and transits of extrasolar planets, providing the possibility to combine both methods to characterize exoplanet systems. I will present results of asteroseismic studies of ~80 exoplanet host stars to accurately determine radii of over 100 planet candidates discovered by Kepler, and to investigate correlations between host-star and planet properties. I will also discuss first results of applying asteroseismology to determine the spin-orbit inclination of exoplanet systems and their implications for theories of hot-Jupiter formation. |
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1515 |
Rogers, Leslie |
Characterizing the Demographics of Exoplanet Bulk Compositions |
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The Kepler Space Telescope has discovered thousands of sub-Saturn-sized transiting planet candidates. To determine the planet mass, the gravitational influence of the planet candidate must be observed, either through radial velocities (RVs) or transit timing variations (TTVs). Constraints on the planet interior structure are possible for the valuable subset of exoplanets with measurements for both the planet mass and the planet radius. The resulting planet average densities can be used for both a compositional interpretation of individual planets and a statistical interpretation of the ensemble properties. Using planet interior structure models, we constrain the bulk compositions of the more than 50 known sub-Saturn-sized transiting planets with measured masses. Our model considers fully differentiated planets comprised of up to four layers: an iron core, a silicate mantle, a water mantle, and a gas envelope. We calculate the planet interior structure by integrating the coupled differential equations describing an evolving self-gravitating body, employing modern equations of state for the iron, silicates, water, and gas. For any individual planet, a wide range of compositions is consistent with the measured mass and radius. We consider the planets as an ensemble, and discuss how thermal evolution, mass loss, and observational biases sculpt the observed planet mass-radius-insolation distribution. Understanding these effects is crucial for constraining the demographics of small planet bulk compositions and for extracting signatures of the planet formation process from the accumulating census of transiting planets with dynamical confirmation. |
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