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מאמרים קשורים
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.
| A Search for Cool Subdwarfs: Stellar Parameters for 134 Candidates
The results of a search for cool subdwarfs are presented. Kinematic (U,V, and W) and stellar parameters (Teff, logg, [Fe/H], andξt) are derived for 134 candidate subdwarfs based onhigh-resolution spectra. The observed stars span 4200K
| 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.
| A search for previously unrecognized metal-poor subdwarfs in the Hipparcos astrometric catalogue
We have identified 317 stars included in the Hipparcos astrometriccatalogue that have parallaxes measured to a precision of better than 15per cent, and the location of which in the(MV,(B-V)T) diagram implies a metallicitycomparable to or less than that of the intermediate-abundance globularcluster M5. We have undertaken an extensive literature search to locateStrömgren, Johnson/Cousins and Walraven photometry for over 120stars. In addition, we present new UBV(RI)C photometry of 201of these candidate halo stars, together with similar data for a further14 known metal-poor subdwarfs. These observations provide the firstextensive data set of RCIC photometry ofmetal-poor, main-sequence stars with well-determined trigonometricparallaxes. Finally, we have obtained intermediate-resolution opticalspectroscopy of 175 stars. 47 stars still lack sufficient supplementaryobservations for population classification; however, we are able toestimate abundances for 270 stars, or over 80 per cent of the sample.The overwhelming majority have near-solar abundance, with theirinclusion in the present sample stemming from errors in the colourslisted in the Hipparcos catalogue. Only 44 stars show consistentevidence of abundances below [Fe/H]=-1.0. Nine are additions to thesmall sample of metal-poor subdwarfs with accurate photometry. Weconsider briefly the implication of these results for clustermain-sequence fitting.
| UBVRI photoelectric photometry of high proper motion stars
UBVRI photoelectric photometry is presented for 269 late spectral type,high proper motion stars belonging to the 'Lowell Proper Motion Survey'and included in the present version of the Hipparcos Input Catalogue.The observations and data reduction are described. The external errorsobtained by comparison of the results with those obtained in otherstudies are presented.
| Spectral classification of high-proper-motion stars
Spectral types have been found for about 900 stars of high proper motioncontained in the Lowell Observatory Northern Hemisphere proper-motionstar survey using all blue-region objective prism plates. The spectralclassification criteria are given. About eighty stars of largetangential velocity have been classified using slit spectrograms takenwith a 36-in. reflector. A new calibration of Luyten's absolutemagnitude vs reduced proper motion relation is made, and its dependenceon spectral type is investigated.
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| קבוצת-כוכבים: | נבל |
| התרוממות ימנית: | 19h16m13.26s |
| סירוב: | +37°04'20.4" |
| גודל גלוי: | 10.972 |
| תנועה נכונה: | -188.6 |
| תנועה נכונה: | 187.9 |
| B-T magnitude: | 11.84 |
| V-T magnitude: | 11.044 |
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