Asteroseismology with the Kepler space telescope is providing not only an improved characterization of exoplanets and their host stars, but also a new window on stellar structure and evolution for the large sample of solar-type stars in the field. We perform a uniform analysis of 22 of the brightest asteroseismic targets with the highest signal-to-noise ratio observed for 1 month each during the first year of the mission, and we quantify the precision and relative accuracy of asteroseismic determinations of the stellar radius, mass, and age that are possible using various methods. We present the properties of each star in the sample derived from an automated analysis of the individual oscillation frequencies and other observational constraints using the Asteroseismic Modeling Portal (AMP), and we compare them to the results of model-grid-based methods that fit the global oscillation properties. We find that fitting the individual frequencies typically yields asteroseismic radii and masses to ∼1% precision, and ages to ∼2.5% precision (respectively 2, 5, and 8 times better than fitting the global oscillation properties). The absolute level of agreement between the results from different approaches is also encouraging, with model-grid-based methods yielding slightly smaller estimates of the radius and mass and slightly older values for the stellar age relative to AMP, which computes a large number of dedicated models for each star. The sample of targets for which this type of analysis is possible will grow as longer data sets are obtained during the remainder of the mission. 15 Remaining affiliations removed due to arXiv error 16 Kepler data are collected by quarters that lasted three months except for the first quarter, which lasted one month (referred as Q1). One month of the other quarters are denoted as Q2.1 for example to refer to the first month of the second quarter.

We present results of a long-baseline interferometry campaign using the PAVO beam combiner at the CHARA Array to measure the angular sizes of five main-sequence stars, one subgiant and four red giant stars for which solarlike oscillations have been detected by either Kepler or CoRoT. By combining interferometric angular diameters, Hipparcos parallaxes, asteroseismic densities, bolometric fluxes, and high-resolution spectroscopy, we derive a full set of near-model-independent fundamental properties for the sample. We first use these properties to test asteroseismic scaling relations for the frequency of maximum power (ν max ) and the large frequency separation (Δν). We find excellent agreement within the observational uncertainties, and empirically show that simple estimates of asteroseismic radii for main-sequence stars are accurate to 4%. We furthermore find good agreement of our measured effective temperatures with spectroscopic and photometric estimates with mean deviations for stars between T eff = 4600-6200 K of −22 ± 32 K (with a scatter of 97 K) and −58 ± 31 K (with a scatter of 93 K), respectively. Finally, we present a first comparison with evolutionary models, and find differences between observed and theoretical properties for the metal-rich main-sequence star HD 173701. We conclude that the constraints presented in this study will have strong potential for testing stellar model physics, in particular when combined with detailed modeling of individual oscillation frequencies.

Since the pioneering observations of Spite & Spite in 1982, the constant lithium abundance of metal-poor (½Fe/H < À1:3) halo stars near the turnoff has been attributed to a cosmological origin. Closer analysis, however, revealed that the observed abundance lies at Á 7 Li $ 0:4 dex below the predictions of big bang nucleosynthesis (BBN). The measurements of deuterium abundances along the lines of sight toward quasars, and the recent data from the Wilkinson Microwave Anisotropy Probe (WMAP), have independently confirmed this gap. We suggest here that part of the discrepancy (from 0.2 to 0.3 dex) is explained by a first generation of stars that efficiently depleted lithium. Assuming that the models for lithium evolution in halo turnoff stars, as well as the Á 7 Li, estimates are correct, we infer that between one-third and one-half of the baryonic matter of the early halo (i.e., $10 9 M ) was processed through Population III stars. This new paradigm proposes a very economical solution to the lingering difficulty of understanding the properties of the Spite plateau and its lack of star-to-star scatter down to ½Fe/H ¼ À2:5. It is moreover in agreement both with the absence of lithium in the most iron-poor turnoff star currently known (HE 1327À2326) and also with new trends of the plateau suggesting its lowmetallicity edge may be reached around ½Fe/H ¼ À2:5. We discuss the role of turbulent mixing associated with enhanced supernovae explosions in the early interstellar medium in this picture. We suggest how it may explain the small scatter and also other recent observational features of the lithium plateau. Finally, we show that other chemical properties of the extremely metal-poor stars (such as carbon enrichment) are also in agreement with significant Population III processing in the halo, provided these models include mass loss and rotationally induced mixing.

Important revisions of the solar model ingredients have appeared recently. We first show that the updated CNO composition suppresses the anomalous position of the Sun in the known galactic enrichment. The following law, He/H = 0.075 + 44.6 O/H in number fraction, is now compatible with all the indicators. We then suggest some directions of investigation to solve the discrepancies between the standard model and solar seismic observations. We finally update our predicted neutrino fluxes using a seismic model and all the recent progress. We get 5.31 +/- 0.6 x 10(6)/cm2/s for the total 8B neutrinos, 66.5 +/- 4.4 SNU and 2.76 +/- 0.4 SNU for the gallium and chlorine detectors, all in remarkable agreement with the detected values including neutrino oscillations for the last two. So, the acoustic modes and detected neutrinos see the same Sun, but the standard model fails to reproduce them.

We examine the internal structure of solar-like stars in detail between 0.8 and 1. 4 and during M _ preÈmain-sequence phase. Recent opacity computations of OPAL along with a new hydrodynamical mixing process have been considered. We also introduce up-to-date nuclear reaction rates and explore the impact of accretion, mixing length parameter, nonsolar distributions among metals, and realistic rotation history. Models predict lithium depletion that we compare to the 7Li content observations of the Sun and four young clusters of di †erent metallicities and age. We show that we can distinguish two phases in lithium depletion : (1) a rapid nuclear destruction in the T Tauri phase before 20 Myr whatever the mass in our range and largely dependent on the extension and temperature of the convective zone, and (2) a second phase where the destruction is slow and moderate and which is largely dependent on the (magneto)hydrodynamic instability located at the base of the convective zone. Regarding composition we show the interest that takes on helium and above all the mixture of heavy elements : carbon, oxygen, silicium, and iron. We outline the importance of the O/Fe ratio. We note a reasonable agreement on lithium depletion for the two best-known cases, the Sun and the Hyades, for solar-like stars. Other clusters suggest that processes which may partly inhibit the predicted preÈmain-sequence depletion cannot be excluded, in particular for stars below D0.9We Ðnally propose di †erent research areas M _ . such as initial stellar models and more realistic atmospheres which could contribute to understanding better this early phase of evolution and which will be the object of subsequent works.

The primary science goal of the Kepler Mission is to provide a census of exoplanets in the solar neighborhood, including the identification and characterization of habitable Earth-like planets. The asteroseismic capabilities of the mission are being used to determine precise radii and ages for the target stars from their solar-like oscillations. Chaplin et al. (2010) published observations of three bright G-type stars, which were monitored during the first 33.5 d of science operations. One of these stars, the subgiant KIC 11026764, exhibits a characteristic pattern of oscillation frequencies suggesting that it has evolved significantly. We have derived asteroseismic estimates of the properties of KIC 11026764 from Kepler photometry combined with ground-based spectroscopic data. We present the results of detailed modeling for this star, employing a variety of independent codes and analyses that attempt to match the asteroseismic and spectroscopic constraints simultaneously. We determine both the radius and the age of KIC 11026764 with a precision near 1%, and an accuracy near 2% for the radius and 15% for the age. Continued observations of this star promise to reveal additional oscillation frequencies that will further improve the determination of its fundamental properties.

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Context. The CoRoT mission is in its third year of observation and the data from the second long run in the galactic centre direction are being analysed. The solar-like oscillating stars that have been observed up to now have given some interesting results, specially concerning the amplitudes that are lower than predicted. We present here the results from the analysis of the star HD 170987. Aims. The goal of this research work is to characterise the global parameters of HD 170987. We look for global seismic parameters such as the mean large separation, maximum amplitude of the modes, and surface rotation because the signal-to-noise ratio in the observations does not allow us to measure individual modes. We also aim to retrieve the parameters of the star and its chemical composition.Methods. We studied the chemical composition of the star through ground-based observations performed with the NARVAL spectrograph. We used several methods to calculate the global parameters from the acoustic oscillations based on CoRoT data. The light curve of the star has been interpolated with inpainting algorithms to reduce the effect of data gaps. Results. We found the power excess related to p modes in the range [400-1200] μHz with a mean large separation of 55.2 ± 0.8 μHz with a probability above 95 % that increases to 55.9 ± 0.2 μHz in a higher frequency range μHz and a rejection level of 1%. A hint of the variation of this quantity with frequency was also found. The rotation period of the star is estimated to be around 4.3 days with an inclination axis of i = 50 • +20 −13 . We measured a bolometric amplitude per radial mode in a range [2.4-2.9] ppm around 1000 μHz. Finally we estimate the stellar mass with a grid of models, M = 1.43 ± 0.05 M , the radius, R = 1.96 ± 0.046 R , and the age ∼2.4 Gyr.