目录
图像
上传图像
DSS Images Other Images
相关文章
Characterizing the Variability of Stars with Early-release Kepler Data
We present a variability analysis of the early-release first quarter ofdata publicly released by the Kepler project. Using the stellarparameters from the Kepler Input Catalog, we have separated the sampleinto 129,000 dwarfs and 17,000 giants and further sub-divided theluminosity classes into temperature bins corresponding approximately tothe spectral classes A, F, G, K, and M. Utilizing the inherent samplingand time baseline of the public data set (30 minute sampling and 33.5day baseline), we have explored the variability of the stellar sample.The overall variability rate of the dwarfs is 25% for the entire sample,but can reach 100% for the brightest groups of stars in the sample. Gdwarfs are found to be the most stable with a dispersion floor of? ~ 0.04 mmag. At the precision of Kepler, >95% of the giantstars are variable with a noise floor of ~0.1 mmag, 0.3 mmag, and 10mmag for the G giants, K giants, and M giants, respectively. Thephotometric dispersion of the giants is consistent with acousticvariations of the photosphere; the photometrically derived predictedradial velocity distribution for the K giants is in agreement with themeasured radial velocity distribution. We have also briefly explored thevariability fraction as a function of data set baseline (1-33 days), atthe native 30 minute sampling of the public Kepler data. To within thelimitations of the data, we find that the overall variability fractionsincrease as the data set baseline is increased from 1 day to 33 days, inparticular for the most variable stars. The lower mass M dwarf, K dwarf,and G dwarf stars increase their variability more significantly than thehigher mass F dwarf and A dwarf stars as the time baseline is increased,indicating that the variability of the lower mass stars is mostlycharacterized by timescales of weeks while the variability of the highermass stars is mostly characterized by timescales of days. A study of thedistribution of the variability as a function of galactic latitudesuggests that sources closer to the galactic plane are more variable.This may be the result of sampling differing populations (i.e., ages) asa function of latitude or may be the result of higher backgroundcontamination that is inflating the variability fractions at lowerlatitudes. A comparison of the M dwarf statistics to the variability of29 known bright M dwarfs indicates that the M dwarfs are primarilyvariable on timescales of weeks or longer presumably dominated by spotsand binarity. On shorter timescales of hours, which are relevant forplanetary transit detection, the stars are significantly less variable,with ~80% having 12 hr dispersions of 0.5 mmag or less.
| 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.
| 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.
| Photometry of dwarf K and M stars
An observational program using UBVRI photometry is presented for 688stars from among the dwarf K and M stars already found spectroscopicallyby Vyssotsky (1958). Of these, 211 have not been observedphotometrically. These observations were obtained over a period ofseveral years at the Kitt Peak National Observatory using a GaAsphotomultiplier with an 0.9 m reflector. Based on night-to-nightvariations in the measures of individual stars, the internal errors maybe estimated to be roughly 0.01 mag for the colors and 0.015 for the Vmagnitudes. The photometric parallaxes reported for each star werecomputed in the manner discussed by Weis (1986).
| Spectral types for proper motion stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80..239B&db_key=AST
| Dwarf M stars found spectrophotometrically .
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..201V&db_key=AST
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
INHABITED SKY
