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מאמרים קשורים
Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Starspot photometry with robotic telescopes. UBV(RI)_C and by light curves of 47 active stars in 1996/97
We present continuous multicolor photometry for 47 stars from October1996 through June 1997. Altogether, 7073 V(RI)_c, UBV, and by datapoints, each the average of three individual readings, were acquiredwith three automatic photoelectric telescopes (APTs) at FairbornObservatory in southern Arizona. Most of our targets arechromospherically active single and binary stars of spectral type G to Kbut there are also four pre-main-sequence objects and three pulsatingstars in our sample. The light variability is generally due torotational modulation of an asymmetrically spotted stellar surface andtherefore precise rotational periods and their seasonal variations aredetermined from Fourier analysis. We also report on photometricvariations of gamma CrB (A0V) with a period of 0.44534 days. All dataare available in numerical form. All data are available from CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Color indices of the Sun and Hyades stars in the WBVR system
Using an original setup at high altitudes, we measured the color indicesof the Sun in the WBVR photometric system relative to standard stars: (W- B)_solar = -0.05, (B - V)_solar = +0.67, and (V - R)_solar = +0.53. Wepresent the WBVR photometry for the Hyades members selected by vanBueren by their space velocities. The solar position is shown intwo-color diagrams relative to Hyades stars and bright G2 V stars. Acomparison of our results with Kurucz's models reveals a discrepancybetween the metallicities of the models and the Hyades members.
| Doppler imaging of stellar surface structure. IX. A high-resolution image of the weak-lined T Tauri star HDE 283572 = V987 Tauri
We present a Doppler image of the T Tauri star HDE 283572 from a set ofhigh-quality spectroscopic line profiles and simultaneous multicolorphotometry from October 1997. Additional photometry throughout theentire observing season was obtained with a robotic telescope and isused to determine the precise photometric period of 1.5495+/-0.0002 daysthat we interpret to be the stellar rotation period. Further relevantastrophysical parameters like mass, luminosity, radius, effectivetemperature, gravity, and elemental abundances are obtained anddiscussed. HDE 283572 shows one of the largest and coolest polar spotsever observed and confirms an earlier map by Joncour et al. fromPic-du-Midi data. We also compare our map with predicted magneticflux-tube distributions from MHD simulations and suggest that the polarspot on HDE 283572 was possibly created by a strong poleward meridionalflow.
| The Hyades: distance, structure, dynamics, and age
{We use absolute trigonometric parallaxes from the Hipparcos Catalogueto determine individual distances to members of the Hyades cluster, fromwhich the 3-dimensional structure of the cluster can be derived.Inertially-referenced proper motions are used to rediscuss distancedeterminations based on convergent-point analyses. A combination ofparallaxes and proper motions from Hipparcos, and radial velocities fromground-based observations, are used to determine the position andvelocity components of candidate members with respect to the clustercentre, providing new information on cluster membership: 13 newcandidate members within 20 pc of the cluster centre have beenidentified. Farther from the cluster centre there is a gradual mergingbetween certain cluster members and field stars, both spatially andkinematically. Within the cluster, the kinematical structure is fullyconsistent with parallel space motion of the component stars with aninternal velocity dispersion of about 0.3 km s(-1) . The spatialstructure and mass segregation are consistent with N-body simulationresults, without the need to invoke expansion, contraction, rotation, orother significant perturbations of the cluster. The quality of theindividual distance determinations permits the cluster zero-age mainsequence to be accurately modelled. The helium abundance for the clusteris determined to be Y =3D 0.26+/-0.02 which, combined with isochronemodelling including convective overshooting, yields a cluster age of625+/-50 Myr. The distance to the observed centre of mass (a conceptmeaningful only in the restricted context of the cluster memberscontained in the Hipparcos Catalogue) is 46.34+/-0.27 pc, correspondingto a distance modulus m-M=3D3.33+/-0.01 mag for the objects within 10 pcof the cluster centre (roughly corresponding to the tidal radius). Thisdistance modulus is close to, but significantly better determined than,that derived from recent high-precision radial velocity studies,somewhat larger than that indicated by recent ground-based trigonometricparallax determinations, and smaller than those found from recentstudies of the cluster convergent point. These discrepancies areinvestigated and explained. } Based on observations made with the ESAHipparcos astrometry satellite. Table~2 is also available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/Abstract.html
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Photometric and spectroscopic monitoring of AA Tau, DN Tau, UX Tau A, T Tau, RY Tau, LK CA 4, and LK CA 7
We report the results of a UBVRI photometric monitoring campaign forthree classical T Tauri stars (AA Tau, DN Tau, and UX Tau A) and twoweak emission line T Tauri stars (Lk Ca 4 and Lk Ca 7). Observationswere obtained at three sites during a core observing period spanning UT1985 October 14 through UT 1985 December 25, with additionalobservations continuing until UT 1986 April 6. Concurrentspectrophotometric observations were obtained for all main program starsexcept Lk Ca 7 and additionally for T Tau, RW Aur, and RY Tau. Periodicphotometric variability, assumed to be the stars' rotation periods, werefound for AA Tau, DN Tau, Lk Ca 4, and Lk Ca 7, respectively, as 8.2,6.3, 3.4, and 5.7 days. Several U-filter flares were observed for Lk Ca4 and Lk Ca 7, which are strongly concentrated toward phases of minimumlight. Correlations are found between H-alpha line strengths and Vmagnitudes for AA Tau and RY Tau. An analysis of absolute colorvariations of classical T Tauri stars confirms that hot spots are thepredominant cause of these stars' variability. Our overall results areconsistent with earlier findings that long-lived cool spots areresponsible for most of the variability found for weak-emission T Tauristars, while temporal hot spots are primarily responsible for theobserved variability found in classical T Tauri stars.
| A catalogue of Fe/H determinations - 1991 edition
A revised version of the catalog of Fe/H determinations published by G.Cayrel et al. (1985) is presented. The catalog contains 3252 Fe/Hdeterminations for 1676 stars. The literature is complete up to December1990. The catalog includes only Fe/H determinations obtained from highresolution spectroscopic observations based on detailed spectroscopicanalyses, most of them carried out with model atmospheres. The catalogcontains a good number of Fe/H determinations for stars from open andglobular clusters and for some supergiants in the Magellanic Clouds.
| The distance and main sequence of the Hyades cluster based on 145 stars with highly accurate proper motions obtained from work on the catalogues FK 5 and PPM
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1991A&A...243..386S&db_key=AST
| A radial-velocity survey of the Hyades
Photoelectric radial-velocity measurements, obtained with external erroras small as 0.1 km/s using the 200-inch Hale telescope at PalomarObservatory during the period 1971-1986, are reported for over 400candidate members (with V magnitude between 6 and 14) of the Hyadescluster. The history of Hyades observations is recalled; the Palomarinstrumentation and observing program are described; the data-reductionand standardization procedures are discussed in detail; and the data arepresented in extensive tables and graphs. About 200 of the stars areclassified as cluster members, including 60 spectroscopic binaries.
| Solar colors on the 13-color system
New photometry for an additional 63 solar-like stars is given. Usingthese new data, three independent methods for defining the solar colorson the 13-color system of photometry give unbiased color estimates forthe sun. The independent color determinations are compared to each otherand to previously selected solar analogs. We suggest that the two starsHR 1662 and HR 3309 deserve additional study as possible solar analogs.An improved absolute calibration of relative colors is also derived forthe 13-color system.
| A catalogue of Fe/H determinations, 1984 edition
The present version of the Cayrel de Strobel et al. (1981) catalog ofFe/H abundance ratio determinations contains 1921 values for 1035 stars,which represents an augmentation over the previous publication of 48 and47 percent, respectively. In addition, the literature search conductedis complete up to December, 1983. Stellar metal abundance, effectivetemperature, spectroscopic gravity, spectral type, and photometricindices are covered.
| UBVRI monitoring of five late-type pre-main-sequence stars
Two T Tauri stars (DF Tau and DK Tau) and three pre-main-sequence Kstars with weak line emission (WK X-Ray 1, WK X-Ray 2, and FK X-Ray 3)were monitored with UBVRI photometry over a 14-night period duringOctober 1982. Neither T Tauri star shows an obvious rotationalmodulation in the light curve, but DF Tau did experience a multi-dayflare-like brightening similar to the events seen in this star byZajtseva and Lyutyi (1976). The light variations of the threeweak-emission stars are well described by sine curves with periods of5.6, 2.8, and 7.0 days, respectively; these values presumably representthe axial rotation periods of these stars. The results provide furtherevidence for K-type pre-main-sequence stars which rotate at least asfast as T Tauri stars but lack strong line and continuum emission.
| Periodic light variations in four pre-main-sequence K stars
Four pre-main-sequence K stars with weak line emission (HD 283447, V410Tau, and two of the X-ray stars studied by Feigelson and Kriss, 1981)have been monitored with UBVRI photometry during seven consecutivenights in 1981 October. All four stars show quasi-sinusoidal lightvariations, apparently due to the presence of large starspots. The lightvariations have amplitudes of from 0.06 to 0.23 mag in yellow light andperiods ranging from 1.9 to 4.1 days. Several significant UV flares werealso observed. The observations indicate that these young stars possessmagnetic surface activity similar to that seen in the RS CVn and BY Drastars. The observed stars fall within rather than below the T Tauri bandin the H-R diagram and have deduced rotational velocities comparable tothose of typical T Tauri stars. Relatively rapid rotation in a late-typepre-main-sequence star is apparently not a sufficient condition forproducing the strong line and continuum emission which characterizestrue T Tauri stars.
| Subluminous late-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...153..195E&db_key=AST
| The Color-Magnitude Diagram of the Hyades Cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962ApJ...136...75J&db_key=AST
| The Hyades and Coma Berenices Star Clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955ApJ...122..209J&db_key=AST
| On the structure of the Hyades cluster
Not Available
| Photoelectric Studies.IV. Color-Luminosity Array for Stars in the Region of the Sun.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1950ApJ...112..141E&db_key=AST
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משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | שור |
| התרוממות ימנית: | 04h22m20.70s |
| סירוב: | +30°25'25.9" |
| גודל גלוי: | 9.109 |
| תנועה נכונה: | 105.7 |
| תנועה נכונה: | -49.1 |
| B-T magnitude: | 9.9 |
| V-T magnitude: | 9.175 |
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