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A Catalog of Temperatures and Red Cousins Photometry for the Hyades
Using Hyades photometry published by Mendoza and other authors,Pinsonneault et al. have recently concluded that Cousins V-I photometrypublished by Taylor & Joner is not on the Cousins system. Extensivetests of the Taylor-Joner photometry and other pertinent results aretherefore performed in this paper. It is found that in part, thePinsonneault et al. conclusion rests on (1) a systematic error inMendoza's (R-I)J photometry and (2) a small error in anapproximate Johnson-to-Cousins transformation published by Bessell. Forthe Taylor-Joner values of (V-R)C, it is found that there arepossible (though not definite) differences of several mmag with otherresults. However, the Taylor-Joner values of (R-I)C data aresupported at the 1 mmag level. Using the (R-I)C data andother published results, an (R-I)C catalog is assembled for146 Hyades stars with spectral types earlier than about K5. For singlestars with multiple contributing data, the rms errors of the catalogentries are less than 4.4 mmag. Temperatures on the Di Benedettoangular-diameter scale are also given in the catalog and are used tohelp update published analyses of high-dispersion values of [Fe/H] forthe Hyades. The best current mean Hyades value of [Fe/H] is found to be+0.103+/-0.008 dex and is essentially unchanged from its previous value.In addition to these numerical results, recommendations are made aboutimproving attitudes and practices that are pertinent to issues likethose raised by Pinsonneault et al.
| Lithium evolution in intermediate age and old open clusters: NGC 752 revisited
We present new high resolution spectroscopic observations of theintermediate age (2 Gyr) open cluster NGC 752.We investigate the Li vs. Teff distribution and we obtain anew accurate determination of the cluster metallicity. We compare theresults for NGC 752 with other intermediate age and old clustersspanning the age range from the Hyades (0.6 Gyr)to NGC 188 (6-8 Gyr). We find that NGC 752 has asolar iron content ([Fe/H]=+0.01±0.04), at variance with earlyreports of sub-solar metallicity. We find that NGC 752 is only slightlymore Li depleted than the younger Hyades and has a Li pattern almostidentical to that observed in the 2 Gyr old IC4651 and NGC 3680. As for the latterclusters, we find that NGC 752 is characterized by a tight Li vs.Teff distribution for solar-type stars, with no evidence fora Li spread as large as the one observed in the solar age solarmetallicity M 67. We discuss these results in theframework of mixing mechanisms and Li depletion on the main sequence(MS). We conclude that the development of a large scatter in Liabundances in old open clusters might be an exception rather than therule (additional observations of old clusters are required), and thatmetallicity variations of the order of ±0.2 dex do notaffect Li depletion after the age of the Hyades.Based on observations collected at Telescopio Nazionale Galileo, LaPalma, Canary Islands.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Membership, rotation, and lithium abundances in the open clusters NGC 2451 A and B
High-resolution spectra of 30 late-type and 9 early-type candidatemembers of the young (50-80 Myr) open clusters NGC 2451 A and Bhave been analyzed in order to complement our previous photometric andX-ray study. Cluster membership of these X-ray selected stars has beenconfirmed or rejected on the basis of radial velocity and Hαchromospheric emission. The metallicity of both clusters seems to beabout solar - contrary to previous investigations. Lithium abundanceshave been determined by two different methods, namely curve-of-growthtechniques and spectrum synthesis, yielding quite consistent results.The pattern of Li abundances versus effective temperature resembles thatof the equally-old Alpha Per cluster, i.e., little Li depletion is seenfor solar-type and earlier-type stars, while towards cooler stars Li ismore and more depleted, possibly showing a star-to-star scatter below 5200 K. The hottest star in our sample shows a Li abundance0.5 dex higher than the meteoritic value. Rotational velocitieshave been determined in order to investigate the supposed dependence ofactivity and Li depletion on rotation.Based on observations performed at the European Southern Observatory, LaSilla/Chile.
| The Second Extreme Ultraviolet Explorer Right Angle Program Catalog
We present the detection of 235 extreme ultraviolet sources, of which169 are new detections, using the Extreme Ultraviolet Explorer's (EUVE)Right Angle Program (RAP) data. This catalog includes observations sincethe first EUVE RAP catalog (1994 January) and covers 17% of the sky. TheEUVE RAP uses the all-sky survey telescopes (also known as``scanners''), mounted at right angles to the Deep Survey andspectrometer instruments, to obtain photometric data in four wavelengthbands centered at ~100 Å (Lexan/B), ~200 Å (Al/Ti/C), ~400Å (Ti/Sb/Al), and ~550 Å (Sn/SiO). This allows the RAP toaccumulate data serendipitously during pointed spectroscopicobservations. The long exposure times possible with RAP observationsprovide much greater sensitivity than the all-sky survey. We presentEUVE source count rates and probable source identifications from theavailable catalogs and literature. The source distribution is similar toprevious extreme ultraviolet (EUV) catalogs with 2% early-type stars,45% late-type stars, 8% white dwarfs, 6% extragalactic, 24% with no firmclassification, and 15% with no optical identification. We also present36 detections of early-type stars that are probably the result ofnon-EUV radiation. We have detected stellar flares from approximately 12sources, including: EUVE J0008+208, M4 star G32-6 (EUVE J0016+198), anew source EUVE J0202+105, EUVE J0213+368, RS CVn V711 Tau (EUVEJ0336+005), BY Draconis type variable V837 Tau (EUVE J0336+259), the newK5 binary EUVE J0725-004, EUVE J1147+050, EUVE J1148-374, EUVE J1334-083(EQ Vir), EUVE J1438-432 (WT 486/487), EUVE J1808+297, and the M5.5estar G208-45 (EUVE J1953+444). We present sample light curves for thebrighter sources.
| Parallaxes and Proper Motions. XX.
Parallaxes and proper motions are listed for 48 stars in 14 fields inthe course of the ongoing astrometric program at Wesleyan and YaleUniversities. A number of resolved binary stars are included in thelist.
| Initial Results of a Comprehensive Ultrasoft Survey of the Einstein IPC Database: Source List and Confirmation of the Selection Procedure
We have carried out a survey of the entire Einstein IPC database (atotal of 5934 sources) to select objects with strong components ofultrasoft X-ray emission (i.e., emission below 0.5 keV). The selectioncriteria are based on ratios of counts within three broad energy bands(i.e., X-ray ``colors''). A total of 516 objects have been selected,with 202 (39%) having been identified through correlations with otherdatabases. Of the currently identified objects, 45% are active galacticnuclei, 28% are stellar objects, 6% are ``normal'' galaxies and galaxyclusters, and the remaining 21% are ``nonstellar'' Galactic objects suchas cataclysmic variables, pulsars, and white dwarfs. We present adiscussion of the survey selection procedure, the list of selectedsources, and discussions of interesting objects from the aforementionedgroups. We discuss the remarkable success of our rather ``lowresolution'' method of estimating spectral shape and present plans forfollow-up studies of the as yet unidentified sources.
| The Multiplicity of the Hyades and Its Implications for Binary Star Formation and Evolution
A 2.2 μm speckle imaging survey of 167 bright (K < 8.5 mag) Hyadesmembers reveals a total of 33 binaries with separations spanning 0.044"to 1.34" and magnitude differences as large as 5.5 mag. Of thesebinaries, 9 are new detections and an additional 20 are now spatiallyresolved spectroscopic binaries, providing a sample from which dynamicalmasses and distances can be obtained. The closest three systems,marginally resolved at Palomar Observatory, were reobserved with the 10m Keck Telescope in order to determine accurate binary star parameters.Combining the results of this survey with previous radial velocity,optical speckle, and direct-imaging Hyades surveys, the detectedmultiplicity of the sample is 98 singles, 59 binaries, and 10 triples. Astatistical analysis of this sample investigates a variety of multiplestar formation and evolution theories. Over the binary separation range0.1"-1.07" (5-50 AU), the sensitivity to companion stars is relativelyuniform, with = 4 mag, equivalent to a mass ratio = 0.23. Accounting for the inability to detect high fluxratio binaries results in an implied companion star fraction (CSF) of0.30 +/- 0.06 in this separation range. The Hyades CSF is intermediatebetween the values derived from observations of T Tauri stars (CSF_TTS =0.40 +/- 0.08) and solar neighborhood G dwarfs (CSF_SN = 0.14 +/- 0.03).This result allows for an evolution of the CSF from an initially highvalue for the pre-main sequence to that found for main-sequence stars.Within the Hyades, the CSF and the mass ratio distribution provideobservational tests of binary formation mechanisms. The CSF isindependent of the radial distance from the cluster center and theprimary star mass. The distribution of mass ratios is best fitted by apower law q^-1.3+/-0.3 and shows no dependence on the primary mass,binary separation, or radial distance from the cluster center. Overall,the Hyades data are consistent with scale-free fragmentation, butinconsistent with capture and disk-assisted capture in small clusters.Without testable predictions, scale-dependent fragmentation and diskfragmentation cannot be assessed with the Hyades data.
| A New and Comprehensive Determination of the Distance to Member Stars of the Hyades
This paper critiques the methods used in the past for estimating thedistances to the stars that make up the Hyades moving cluster, anddevelops one which is new and comprehensive. We develop a formalism forthe application of stochastic restrictions to the adjustment parameters(velocity components and distances) and test it on constructed clustermodels. We perform model calculations with fictitious model starclusters in which the `true' values of the input parameters (ie.positions, distances and velocity components) are therefore known. Thecomparison of the distances recovered by different methods with the trueinput distances shows our approach to be very superior to thetraditional ones that estimate distances by the method of streamparallaxes without restricting the adjustment parameters. Applying ouralgorithm to the Hyades, we assume a dispersion of 0.25 kps in eachcoordinate about a common value for the velocity components of thecluster members and a dispersion of 5pc about the distance to thecluster's centre for the distances to the stars in the cluster. Underthese stochastic restrictions, we analyse the known estimates (ie.measurements) of trigonometric parallaxes, sets of high-precision propermotion pairs and high-precision radial velocities subject to theabove-stated stochastic constraints, and as a result estimate thecluster's centre to be at a distance of 45.8+/-1.25 (standard error) pc.
| Lithium abundance in binaries of the Hyades open cluster.
We have derived accurate and homogeneous lithium abundances in 49 MainSequence binary systems belonging to the Hyades open cluster by using adeconvolution method to determine individual magnitudes and colors forthe primary and secondary components of the binary. The input parametersof the model are the observed Li equivalent width, the actual distanceto the binary, the integrated apparent magnitude and the integratedcolors of the binaries -BV(RI)_K_. We show that the general behavior isthe same in binaries and in single stars (Li is depleted faster in Kstars than in G stars and there is a deep dip for mid-F stars). However,there is a larger scatter in the abundances of binary systems than insingle stars. Moreover, in general, binary systems have anoverabundance, which is more conspicuous in close binaries. In fact,there is a cut-off period, which can be estimated as P_orb_~9d. Thisvalue is in excellent agreement with the theoretical prediction of Zahn(1994).
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Determination of atmospheric parameters of T Tauri stars.
The inferred effective temperatures (T_eff_) and surface gravities(logg) of T Tauri stars (TTS) are usually contaminated by the presenceof a non stellar continuum emission (veiling) and the strongchromospheric activity characteristic of these objects. In this work, wedevelop a method to determine T_eff_'s and surface gravities of a groupof TTS. This method is based on the comparison between observed andtheoretical molecular and atomic line depth ratios being thereforeinsensitive to the influence of veiling. We show the strong dependenceof our line depth ratios upon gravity and temperature. The resultinggravities, as expected for TTS, average between the values of dwarf andgiant stars. Previously published gravities for each of our stars varywidely due in part to the differences in the adopted visual extinction,veiling (if ever considered) and methods of assessing the stellarluminosity. Our values of T_eff_ and logg have the uniqueness of beingentirely derived from high resolution data and are not affected bycircumstellar extinction or veiling. They therefore serve as morereliable input parameters for future spectral synthesis analyses of TTauri stars requiring model atmospheres. We provide a table relatingtheoretical line depth ratios with T_eff_ and log g for easy assessmentof TTS fundamental parameters.
| ROSAT All-Sky Survey Observations of the Hyades Cluster
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...448..683S&db_key=AST
| The Lithium Dip in M67: Comparison with the Hyades, Praesepe, and NGC 752 Clusters
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...446..203B&db_key=AST
| Photometric Survey Near the Main Galactic Meridian - Part One - Photoelectric Stellar Magnitudes and Colours in the UBVR System
Not Available
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| ROSAT X-ray luminosity functions of the Hyades dK and dM stars
Long-duration ROSAT PSPC pointed observations of the Hyades open starcluster are performed. The Hyades dK and XLFs from the presentobservations are compared with published Einstein dK/dM XLFs. The HyadesdK binaries have significantly higher L(X) than the Hyades dK stars.However, all these binaries have relatively long periods (greater thanabout 1 yr), and hence the L(X) levels cannot be attributed to theenhanced activity expected in short-period, 'BY Dra-type' systems. It isalso shown that the effect cannot be due simply to the summedluminosities of the component stars.
| Low-Mass Stars in the Hyades
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993MNRAS.265..785R&db_key=AST
| Lithium in the Hyades. I - New observations
Results are presented of new observations, carried out at Li 6707 A, on68 main-sequence members of the Hyades cluster with spectral typesranging from late F to and early K, and their surface lithium abundanceLi/H is related to their mass, age, and initial composition. It is foundthat, for the sample as a whole, the observed distribution of lithiumabundances is inconsistent with the hypothesis of a unique relationshipbetween lithium abundance and mass. Moreover, is strong observationalevidence for main-sequence lithium depletion when the data are comparedwith observations in younger clusters, even for masses that are notpredicted to experience such depletion in standard stellar models.
| ICCD speckle observations of binary stars. VII - A duplicity survey of the Hyades cluster
The Hyades cluster is the nearest open cluster to the solar system, andits distance has long been a contentious issue. In order to expand thesample of Hyades binaries with potentially short-period visual orbits, aspeckle survey of 153 bright Hyades stars for possible multiplicity wasconducted at the KPNO 4 m Mayall telescope on November 23-27, 1991. Ofthese, one is graded as a suspected new binary, three are graded aspossible new binaries, and three are graded as definite new binaries,one of which has been confirmed from examination of an archivalobservation from 1989. Of these seven new visual resolutions, six havepossible spectroscopic components, two of which are probably the objectsobserved here, three certainly are not, and one may or may not be thecomponent observed.
| Proper motions from Schmidt plates. II - The Hyades
COSMOS scans of photographic plates taken by the Palomar Oschin Schmidttelescope and by the UK Schmidt telescope are used to obtain propermotions for about 450,000 stars within a 112-sq-deg region covering partof the Hyades luster. With epoch differences of 33 to 37 yr, propermotions accurate to 6-12 milliarcsec/yr are obtained, and 393 candidateHyades to a limiting magnitude of about 15.5, including at least two newwhite dwarf candidates, are identified. The main-sequence luminosityfunction determined from this sample is similar to that defined by localfield stars, with a broad maximum at about +12. Both the line-of-sightand surface density distributions show evidence for significant masssegregation; the overall proper motion distribution suggests a tightcore centered within a much broader distribution. A total mass of410-480 solar masses and a gravitational binding radius of about 10.5 pcare derived.
| 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
| Hamilton echelle spectra of young stars. I - Optical veiling
An extensive set of veiling measurements of T Tauri stars coveringalmost the entire optical spectrum is presented. These are based onHamilton echelle spectra obtained during 1987-1989. A full range of TTauri stars, from 'weak' to 'continuum' stars is studied; in some cases,several spectra of a given target are seen in which the veiling haschanged, occasionally dramatically. Veilings are determined using twonew methods: one which concentrates on the residual intensities ofselected spectral lines, and the other which compares theautocorrelation functions for a T Tauri star and a veiled standard. Thegeneral shape of the veiling is often as predicted by accretion diskmodels: almost flat in the red and increasing in the blue. Cooler starshave generally higher veiling, implying that the veiling power isrelatively independent of stellar mass. The relation between veiling andthe narrow and broad emission lines supports a nonstellar origin for theveiling and broad line components, and a stellar origin for the narrowlines.
| Parallaxes of stars in the Hyades Cluster region - A comparison of hand and automatic measures
Parallaxes and proper motions are presented for 30 members of the HyadesCluster and 223 field stars in 13 fields located near the center of thecluster. The series of photographic plates are extensive and they weremeasured twice; first, by hand, using a conventional two-screw measuringmachine, and also with a PDS microdensitometer. A comparison of the twosets of measures reveals that the internal and external errors inparallax average about + or - 0.005 arcsec for the central stars fromautomatic PDS measures and about twice this amount for the data measuredby hand. The parallaxes of the member stars yield a distance modulus of3.30, in excellent agreement with the average of many prior distancedeterminations for the cluster. The parallaxes of the field starsconfirm a small amount of coma or higher-order terms in the opticalsystem of the Van Vleck refractor. They also confirm that, within afield of one half degree radius centered on the optical axis and over arange in visual magnitude from 8.5 to 13, the errors in parallax varyonly slightly over the most optimum conditions.
| Very active chromosphere stars and the age, chromosphere activity relation
The wide range of objects in stellar superclusters and groups near thesun is used in an attempt to define normal stellar chromosphericbehavior, with which 'very active chromosphere' (VAC) stars can beisolated. Two chromosphere signatures, soft X-ray flux, and Mg II h andk line flux, are discussed. The X-ray flux is of limited use in thisregard because of a wide range of variation with time, although themaximum values are well defined for stars of a given age. The VAC stars,which have an excessive X-ray flux, also have an excessive bolometricflux. The ratio of the Mg II h and k (and Ca II H and K) line emissionand the total bolometric emission, R(hk) decreases with bolometricluminosity. The rate of decrease in log R(hk), 0.175 (35.00 - logLBOL), is not very dependent on stellar age, but the zeropoint at log LBOL = 35.00 decades varies from log R(hk) =-4.45 decades for main-sequence stars in the Pleiades supercluster(200-300 million yr) to - 4.91 decades for those in the HR 1614 group (8billion yr). The age dependence of R(hk) is clearly demonstrated notonly by the supercluster and group stars but by the 'Mount Wilsonsample' of objects that have been observed in Ca II H and K for over 15years (e.g., Noyes et al., 1984). Several determinations (e.g.,Soderblom and Clements, 1987) have established a linear relation betweenR(hk) and R(HK). Some 50 stars in the Mount Wilson sample havewell-established luminosities and space motions (e.g., Eggen, 1989) thatallow the separation of young and old disk stars in velocity space(Eggen, 1989). The young disk stars all have values of R(hk) thatidentify them as having ages less than the youngest Hyades superclustermembers (about 600 million yr).
| Determining the temperatures of solar-type stars - Do star spots produce color anomalies?
The available evidence pertaining to color 'anomalies' in Hyades dwarfsare examined in detail in order to understand how the determine thetemperatures of solar-type stars. The evidence indicates that thetemperatures of these stars are not seriously skewed by their spots.Simpler explanations which can produce the observed effects arediscussed.
| 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.
| The Einstein Observatory survey of stars in the Hyades cluster region
The paper reports the results of an extensive X-ray study of the Hyadesregion and improves on previous studies by using refined X-ray sourcedetection algorithms and the complete set of Einstein Observatory IPCexposures covering the Hyades cluster region (a total of 63 1 x 1 degimages). Maximum likelihood integral X-ray luminosity functions werecomputed for the Hyades stars for given color index (B-V) ranges. Thepresent results agree substantially with a previous survey about theubiquity of the stellar activity in the Hyades cluster, especially amongsolar-type stars. The result of Stern et al. (1981) that stellar X-rayemission is dependent on stellar age is confrimed.
| Trigonometric parallaxes determined with the Yerkes Observatory 40 inch refractor. VII
Parallaxes and proper motions based on observations with the 40 in.refractor of the Yerkes Observatory are presented for 21 stars. Plateswere measured on the MADRAF PDS microdensitometer in Madison, WI,yielding an increase in precision of a factor larger than 2 overprevious parallaxes measured on the Yerkes measuring machine. Theaverage standard error of these parallaxes is + or - 0.0023 arcsec.Several of these stars are subdwarfs.
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Наблюдательные данные и астрометрия
| Созвездие: | Телец |
| Прямое восхождение: | 04h30m34.88s |
| Склонение: | +15°44'02.3" |
| Видимая звёздная величина: | 8.847 |
| Собственное движение RA: | 99.6 |
| Собственное движение Dec: | -21.7 |
| B-T magnitude: | 9.93 |
| V-T magnitude: | 8.937 |
Каталоги и обозначения:
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