109 research outputs found

    Impact of microphysics on tropical precipitation extremes in a global storm-resolving model

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    The impact of microphysics on tropical precipitation extremes is explored with a global storm-resolving model by modifying the terminal velocity of raindrops. Depending on the time scales, precipitation extremes respond differently. Hourly extremes are influenced dynamically through the microphysical modulation on the convective updraft speed, as a faster terminal velocity of raindrops increases the updraft speed by reducing the total condensates in the atmosphere which increases the updraft buoyancy. However, the response of daily precipitation extremes is more sensitive to the microphysical impact on convective organization. By being more organized with decreasing terminal velocity, daily precipitation extremes are enhanced due to increased precipitation efficiency and intensified updrafts. Thus, the results suggest that microphysics, despite often occurring at small spatial scales, can influence the circulation at larger scales, and the microphysical imprint across different time scales plays an important role in regulating tropical precipitation extreme

    Kepler-47: A Transiting Circumbinary Multi-Planet System

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    We report the detection of Kepler-47, a system consisting of two planets orbiting around an eclipsing pair of stars. The inner and outer planets have radii 3.0 and 4.6 times that of the Earth, respectively. The binary star consists of a Sun-like star and a companion roughly one-third its size, orbiting each other every 7.45 days. With an orbital period of 49.5 days, eighteen transits of the inner planet have been observed, allowing a detailed characterization of its orbit and those of the stars. The outer planet's orbital period is 303.2 days, and although the planet is not Earth-like, it resides within the classical "habitable zone", where liquid water could exist on an Earth-like planet. With its two known planets, Kepler-47 establishes that close binary stars can host complete planetary systems.Comment: To appear on Science Express August 28, 11 pages, 3 figures, one table (main text), 56 pages, 28 figures, 10 table

    The architecture of the hierarchical triple star KOI 928 from eclipse timing variations seen in Kepler photometry

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    We present a hierarchical triple star system (KIC 9140402) where a low mass eclipsing binary orbits a more massive third star. The orbital period of the binary (4.98829 Days) is determined by the eclipse times seen in photometry from NASA's Kepler spacecraft. The periodically changing tidal field, due to the eccentric orbit of the binary about the tertiary, causes a change in the orbital period of the binary. The resulting eclipse timing variations provide insight into the dynamics and architecture of this system and allow the inference of the total mass of the binary (0.424±0.017M0.424 \pm 0.017 \text{M}_\odot) and the orbital parameters of the binary about the central star.Comment: Submitted to MNRAS Letters. Additional tables with eclipse times are included here. The Kepler data that was used for the analysis of this system (Q1 through Q6) will be available on MAST after June 27, 201

    Discovery of a Third Transiting Planet in the Kepler-47 Circumbinary System

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    Of the nine confirmed transiting circumbinary planet systems, only Kepler-47 is known to contain more than one planet. Kepler-47 b (the "inner planet") has an orbital period of 49.5 days and a radius of about 3 R⊕. Kepler-47 c (the "outer planet") has an orbital period of 303.2 days and a radius of about 4.7 R⊕. Here we report the discovery of a third planet, Kepler-47 d (the "middle planet"), which has an orbital period of 187.4 days and a radius of about 7 R⊕. The presence of the middle planet allows us to place much better constraints on the masses of all three planets, where the 1σranges are less than 26 M⊕, between 7–43 M⊕, and between 2–5 M⊕ for the inner, middle, and outer planets, respectively. The middle and outer planets have low bulk densities, with ρ_(middle) < 0.68 g cm^(−3) and ρ_(outer) < 0.26 g cm^(−3) at the 1σ level. The two outer planets are "tightly packed," assuming the nominal masses, meaning no other planet could stably orbit between them. All of the orbits have low eccentricities and are nearly coplanar, disfavoring violent scattering scenarios and suggesting gentle migration in the protoplanetary disk

    Biomolecular Filters for Improved Separation of Output Signals in Enzyme Logic Systems Applied to Biomedical Analysis

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    Biomolecular logic systems processing biochemical input signals and producing "digital" outputs in the form of YES/NO were developed for analysis of physiological conditions characteristic of liver injury, soft tissue injury and abdominal trauma. Injury biomarkers were used as input signals for activating the logic systems. Their normal physiological concentrations were defined as logic-0 level, while their pathologically elevated concentrations were defined as logic-1 values. Since the input concentrations applied as logic 0 and 1 values were not sufficiently different, the output signals being at low and high values (0, 1 outputs) were separated with a short gap making their discrimination difficult. Coupled enzymatic reactions functioning as a biomolecular signal processing system with a built-in filter property were developed. The filter process involves a partial back-conversion of the optical-output-signal-yielding product, but only at its low concentrations, thus allowing the proper discrimination between 0 and 1 output values

    Transiting circumbinary planets Kepler-34 b and Kepler-35 b

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    Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated the existence of a ‘circumbinary planet’ orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289 days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun’s mass) every 131 days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million

    The Updated BaSTI Stellar Evolution Models and Isochrones: I. Solar Scaled Calculations

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    We present an updated release of the BaSTI (a Bag of Stellar Tracks and Isochrones) stellar model and isochrone library for a solar scaled heavy element distribution. The main input physics changed from the previous BaSTI release include the solar metal mixture, electron conduction opacities, a few nuclear reaction rates, bolometric corrections, and the treatment of the overshooting efficiency for shrinking convective cores. The new model calculations cover a mass range between 0.1 and 15 Msun, 22 initial chemical compositions between [Fe/H]=-3.20 and +0.45, with helium to metal enrichment ratio dY /dZ=1.31. The isochrones cover an age range between 20 Myr and 14.5 Gyr, take consistently into account the pre-main sequence phase, and have been translated to a large number of popular photometric systems. Asteroseismic properties of the theoretical models have also been calculated. We compare our isochrones with results from independent databases and with several sets of observations, to test the accuracy of the calculations. All stellar evolution tracks, asteroseismic properties and isochrones are made available through a dedicated Web site

    Discovery of a Third Transiting Planet in the Kepler-47 Circumbinary System

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    Of the nine confirmed transiting circumbinary planet systems, only Kepler-47 is known to contain more than one planet. Kepler-47 b (the "inner planet") has an orbital period of 49.5 days and a radius of about 3 R⊕. Kepler-47 c (the "outer planet") has an orbital period of 303.2 days and a radius of about 4.7 R⊕. Here we report the discovery of a third planet, Kepler-47 d (the "middle planet"), which has an orbital period of 187.4 days and a radius of about 7 R⊕. The presence of the middle planet allows us to place much better constraints on the masses of all three planets, where the 1σranges are less than 26 M⊕, between 7–43 M⊕, and between 2–5 M⊕ for the inner, middle, and outer planets, respectively. The middle and outer planets have low bulk densities, with ρ_(middle) < 0.68 g cm^(−3) and ρ_(outer) < 0.26 g cm^(−3) at the 1σ level. The two outer planets are "tightly packed," assuming the nominal masses, meaning no other planet could stably orbit between them. All of the orbits have low eccentricities and are nearly coplanar, disfavoring violent scattering scenarios and suggesting gentle migration in the protoplanetary disk
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