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Verifying Asteroseismically Determined Parameters of Kepler Stars Using Hipparcos Parallaxes: Self-consistent Stellar Properties and Distances
Accurately determining the properties of stars is of prime importancefor characterizing stellar populations in our Galaxy. The field ofasteroseismology has been thought to be particularly successful in suchan endeavor for stars in different evolutionary stages. However, tofully exploit its potential, robust methods for estimating stellarparameters are required and independent verification of the results ismandatory. With this purpose, we present a new technique to obtainstellar properties by coupling asteroseismic analysis with the InfraRedFlux Method. By using two global seismic observables and multi-bandphotometry, the technique allows us to obtain masses, radii, effectivetemperatures, bolometric fluxes, and hence distances for field stars ina self-consistent manner. We apply our method to 22 solar-likeoscillators in the Kepler short-cadence sample, that have accurateHipparcos parallaxes. Our distance determinations agree to better than5%, while measurements of spectroscopic effective temperatures andinterferometric radii also validate our results. We briefly discuss thepotential of our technique for stellar population analysis and models ofGalactic Chemical Evolution.
| Accurate fundamental parameters and detailed abundance patterns from spectroscopy of 93 solar-type Kepler targets
We present a detailed spectroscopic study of 93 solar-type stars thatare targets of the NASA/Kepler mission and provide detailed chemicalcomposition of each target. We find that the overall metallicity is wellrepresented by Fe lines. Relative abundances of light elements (CNO) andα elements are generally higher for low-metallicity stars. Ourspectroscopic analysis benefits from the accurately measured surfacegravity from the asteroseismic analysis of the Kepler light curves. Theaccuracy on the log g parameter is better than 0.03 dex and is heldfixed in the analysis. We compare our Teff determination witha recent colour calibration of VT-KS [TYCHO Vmagnitude minus Two Micron All Sky Survey (2MASS) KSmagnitude] and find very good agreement and a scatter of only 80 K,showing that for other nearby Kepler targets, this index can be used.The asteroseismic log g values agree very well with the classicaldetermination using Fe I-Fe II balance, although we find a smallsystematic offset of 0.08 dex (asteroseismic log g values are lower).The abundance patterns of metals, α elements and the lightelements (CNO) show that a simple scaling by [Fe/H] is adequate torepresent the metallicity of the stars, except for the stars withmetallicity below -0.3, where α-enhancement becomes important.However, this is only important for a very small fraction of the Keplersample. We therefore recommend that a simple scaling with [Fe/H] beemployed in the asteroseismic analyses of large ensembles of solar-typestars.
| A Uniform Asteroseismic Analysis of 22 Solar-type Stars Observed by Kepler
Asteroseismology with the Kepler space telescope is providing not onlyan improved characterization of exoplanets and their host stars, butalso a new window on stellar structure and evolution for the largesample of solar-type stars in the field. We perform a uniform analysisof 22 of the brightest asteroseismic targets with the highestsignal-to-noise ratio observed for 1 month each during the first year ofthe mission, and we quantify the precision and relative accuracy ofasteroseismic determinations of the stellar radius, mass, and age thatare possible using various methods. We present the properties of eachstar in the sample derived from an automated analysis of the individualoscillation frequencies and other observational constraints using theAsteroseismic Modeling Portal (AMP), and we compare them to the resultsof model-grid-based methods that fit the global oscillation properties.We find that fitting the individual frequencies typically yieldsasteroseismic radii and masses to ~1% precision, and ages to ~2.5%precision (respectively, 2, 5, and 8 times better than fitting theglobal oscillation properties). The absolute level of agreement betweenthe results from different approaches is also encouraging, withmodel-grid-based methods yielding slightly smaller estimates of theradius and mass and slightly older values for the stellar age relativeto AMP, which computes a large number of dedicated models for each star.The sample of targets for which this type of analysis is possible willgrow as longer data sets are obtained during the remainder of themission.
| Photometric Study of Kepler Asteroseismic Targets
Reported are UBV and uvby? observations of 15 candidates for Keplerprimary asteroseismic targets and 14 other stars in the Kepler field,carried out at the M.G. Fracastoro station of the Catania AstrophysicalObservatory. These data serve to plot the 29 stars in two-parameterdiagrams with the photometric indices (such as B-V or?m1) and the atmospheric parameters (such as the MKtype or [Fe/H]) as coordinates. The two-parameter diagrams show noevidence of interstellar reddening. The photometric indices B-V and? are then used to derive photometric effective temperatures,Teff(B-V) and Teff(?). ForTeff(B-V)>6400 K, the photometric effective temperaturesturn out to be systematically higher than spectroscopic effectivetemperatures by 311±34 K and 346±91 K forTeff(B-V) and Teff(?), respectively. ForTeff(B-V)<6250 K, the agreement betweenTeff(B-V) and the spectroscopic effective temperatures isvery good. The photometric surface gravities, derived from c1and ?, show a range of about a factor of two greater than theirspectroscopic counterparts do.
| Kepler primary asteroseismic targets - ground-based study .
Reported are results of ground-based spectroscopic and photometricobservations of Kepler primary asteroseismic targets. We determine log T_eff, log g, [Fe/H], vsin i and the mean radial velocity, v_r, forall these stars. For new spectroscopic binaries, we provide orbitalsolutions. Finally, we compute evolutionary models using Monte Carlosimulations.
| Spectroscopic Study of Kepler Asteroseismic Targets
Reported are spectroscopic observations of 15 candidates for Keplerprimary asteroseismic targets and 14 other stars in the Kepler field,carried out at three observatories. For all these stars, the radialvelocities, effective temperature, surface gravity, metallicity, and theprojected rotational velocity are derived from two separate sets of databy means of two independent methods. In addition, MK type is estimatedfrom one of these sets of data.Three stars, HIP94335, HIP94734, and HIP94743, are found to havevariable radial-velocity. For HIP94335 = FLLyr, a well-known Algol-typeeclipsing variable and a double-lined spectroscopic binary, the orbitalelements computed from our data agree closely with those of Popper etal. For HIP94734 and HIP94743 = V2077 Cyg, which we discover to besingle-lined systems, orbital elements are derived. In addition, fromour value of the orbital period and the Hipparcos epoch photometry,HIP94743 is demonstrated to be a detached eclipsing binary.
| The new space telescope Kepler and its asteroseismological targets .
We present primary and secondary asteroseismological targets for Kepler,the new NASA space mission. We derive log T_eff and logL/Lȯ values for the selected stars and we put the starsin the log L/Lȯ - log T_eff diagram. Then, we presentour program of ground-based spectroscopic and photometric observationsof the selected targets and we show first results obtained from theseobservations.
| A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)
The LSPM catalog is a comprehensive list of 61,977 stars north of theJ2000 celestial equator that have proper motions larger than 0.15"yr-1 (local-background-stars frame). The catalog has beengenerated primarily as a result of our systematic search for high propermotion stars in the Digitized Sky Surveys using our SUPERBLINK software.At brighter magnitudes, the catalog incorporates stars and data from theTycho-2 Catalogue and also, to a lesser extent, from the All-SkyCompiled Catalogue of 2.5 million stars. The LSPM catalog considerablyexpands over the old Luyten (Luyten Half-Second [LHS] and New LuytenTwo-Tenths [NLTT]) catalogs, superseding them for northern declinations.Positions are given with an accuracy of <~100 mas at the 2000.0epoch, and absolute proper motions are given with an accuracy of ~8 masyr-1. Corrections to the local-background-stars propermotions have been calculated, and absolute proper motions in theextragalactic frame are given. Whenever available, we also give opticalBT and VT magnitudes (from Tycho-2, ASCC-2.5),photographic BJ, RF, and IN magnitudes(from USNO-B1 catalog), and infrared J, H, and Ks magnitudes(from 2MASS). We also provide an estimated V magnitude and V-J color fornearly all catalog entries, useful for initial classification of thestars. The catalog is estimated to be over 99% complete at high Galacticlatitudes (|b|>15deg) and over 90% complete at lowGalactic latitudes (|b|>15deg), down to a magnitudeV=19.0, and has a limiting magnitude V=21.0. All the northern starslisted in the LHS and NLTT catalogs have been reidentified, and theirpositions, proper motions, and magnitudes reevaluated. The catalog alsolists a large number of completely new objects, which promise to expandvery significantly the census of red dwarfs, subdwarfs, and white dwarfsin the vicinity of the Sun.Based on data mining of the Digitized Sky Surveys (DSSs), developed andoperated by the Catalogs and Surveys Branch of the Space TelescopeScience Institute (STScI), Baltimore.Developed with support from the National Science Foundation (NSF), aspart of the NASA/NSF NStars program.
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
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Observation and Astrometry data
| Constellation: | こと座 |
| Right ascension: | 19h16m34.90s |
| Declination: | +40°02'50.4" |
| Apparent magnitude: | 9.512 |
| Proper motion RA: | 11.4 |
| Proper motion Dec: | 175.5 |
| B-T magnitude: | 10.223 |
| V-T magnitude: | 9.571 |
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