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uvby - β Photoelectric Photometry of the Open Cluster α Per
Absolute photoelectric photometry of stars in the direction of the OpenCluster α Per has been secured and is presented along with ananalysis reinforced with all the available data in Strömgrenuvby-β photometry compiled from the literature. Cluster membershipis analyzed and the physical characteristics of the stars have beendeduced. The membership determined in this paper is compared with thatof proper motion studies and Hipparcos.
| Precision Kinematics and Related Parameters of the α Persei Open Cluster
A kinematical study of the nearby open cluster α Persei ispresented based on the astrometric proper motions and positions in theTycho-2 catalog and Second USNO CCD Astrographic Catalog (UCAC2). Usingthe astrometric data and photometry from the Tycho-2 and ground-basedcatalogs, 139 probable members of the cluster are selected, 18 of themnew. By the classical convergent point method, systematic motions ofstars inside the cluster and velocity dispersions are estimated. Asdirectly observed, the upper limit on the internal velocity dispersionper coordinate is 1.1 km s-1. The actual velocity dispersionis much smaller than that value, since all of it appears to come fromthe expected errors of the astrometric proper motions. The relativeposition of the convergent point with respect to the cluster starsyields the ``astrometric'' radial velocity, which turns out larger by afew km s-1 than the mean observed spectroscopic radialvelocity. This implies an overall contraction of the cluster. Kinematicparallaxes are computed for each member, and an improved H-R diagram isconstructed. An age of 52 Myr is determined by isochrone fitting. Thestar α Per itself fits an isochrone of this age computed withovershooting from the boundary of the convective zone. The theoreticalmass of the star α Per is 6.65 Msolar. With respect tothe common center of mass, half of the higher mass members (earlier thanG) are located within a radius of 10.3 pc. The cluster appears to beroughly twice as large, or as sparse, as the Pleiades, retainingnonetheless a similar dynamical coherence. The low rate of binaries isanother feature of this cluster, where we find only about 20% of membersto be known or suspected spectroscopic, astrometric, or visual binariesor multiple systems. X-ray emitters in the cluster appear to have thesame dispersion of internal velocities as the rest of the membership.The cluster is surrounded by an extended, sparse halo of comovingdwarfs, which are found by combining the proper-motion data from UCAC2with Two Micron All-Sky Survey infrared photometry. Since many of theseexternal stars are outside the tidal radius, the cluster being in anactive stage of disintegration or evaporation could be considered. Thishypothesis is not supported by the weak compression and thenonmeasurable velocity dispersion found in the kinematic analysis. Asearch for stars ejected from the α Persei cluster is carried outby tracking a large number of nearby stars 70 Myr back in time andmatching their positions with the past location of the cluster. Only oneplausible ejection is found prior to 10 Myr ago. The nearby star GJ 82,an active M dwarf with a strong Hα emission, is likely a formermember ejected 47 Myr ago at 5 km s-1.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
| Spectrophotometry of 237 Stars in 7 Open Clusters
Spectrophotometry is presented for 237 stars in 7 nearby open clusters:Hyades, Pleiades, Alpha Persei, Praesepe, Coma Berenices, IC 4665, andM39. The observations were taken by Lee McDonald and David Bursteinusing the Wampler single-channel scanner on the Crossley 0.9m telescopeat Lick Observatory from July 1973 through December 1974. Sixteenbandpasses spanning the spectral range 3500 Angstroms to 7780 Angstromswere observed for each star, with bandwidths 32Angstroms, 48 Angstromsor 64 Angstroms. Data are standardized to the Hayes-Latham system tomutual accuracy of 0.016 mag per passband. The accuracy of thespectrophotometry is assessed in three ways on a star-by-star basis.First, comparisons are made with previously published spectrophotometryfor 19 stars observed in common. Second, (B-V) colors and uvby colorsare compared for 236 stars and 221 stars, respectively. Finally,comparsions are made for 200 main sequence stars to the spectralsynthesis models of Kurucz, fixing log g = 4.0 and [Fe/H] = 0.0, andonly varying effective temperature. The accuracy of tests using uvbycolors and the Kurucz models are shown to track each other closely,yielding an accuracy estimate (1 sigma ) of 0.01 mag for the 13 colorsformed from bandpasses longward of the Balmer jump, and 0.02 mag for the3 colors formed from the three bandpasses below the Balmer jump. Incontrast, larger scatter is found relative to the previously publishedspectrophotometry of Bohm-Vitense & Johnson (16 stars in common) andGunn & Stryker (3 stars). We also show that the scatter in the fitsof the spectrophotometric colors and the uvby filter colors is areasonable way to identify the observations of which specific stars areaccurate to 1 sigma , 2 sigma , .... As such, the residuals from boththe filter color fits and the Kurucz model fits are tabulated for eachstar where it was possible to make a comparison, so users of these datacan choose stars according to the accuracy of the data that isappropriate to their needs. The very good agreement between the modelsand these data verifies the accuracy of these data, and also verifiesthe usefulness of the Kurucz models to define spectrophotometry forstars in this temperature range (>5000 K). These data define accuratespectrophotometry of bright, open cluster stars that can be used as asecondary flux calibration for CCD-based spectrophotometric surveys.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| The X-ray properties of the young open cluster around α Persei.
We present ROSAT PSPC pointed observations of the 50Myr old α Peropen cluster. The X-ray observations, which were carried out as a rasterscan, cover an area of about 10deg^2^. In total, we detect about 160X-ray sources, 88 of which have an optical counterpart (within 30arcsec)associated with α Per cluster candidates. Within the centralregion of our field of view, which is characterized by a limitingsensitivity L_X_~10^28.8-29^erg/sec, we detect basically all late-F, Gand K stars, while the detection rate among the M dwarfs is on the orderof 60%. Given the sensitivity of our X-ray observations, the lowerdetection rate among the very low mass objects is consistent with theROSAT results obtained for the Pleiades cluster. Although stars in eachcolor range show a large spread in X-ray luminosity, the maximal X-rayluminosities appear to decrease from the range of late-F - G type starsto the M-type dwarfs. We interpret this as due to the fact that themaximum X-ray luminosity cannot exceed the saturation levelL_X_/L_bol_~10^-3^, and is hence a function of the bolometricluminosity. The availability of rotational velocities for many of theX-ray detected objects permits us to study correlations between rotationand X-ray activity. For B-V_o_>0.6, at a given mass, the weakestX-ray sources are slow rotators, while the strongest X-ray sources arerapid rotators. The relation between L_X_/L_bol_ and rotation we findfor the α Per low mass stars is the same as previously determinedfor low mass stars in the Pleiades, and a similar relation is found oncorrelating L_X_/L_bol_ with rotation period. Using directly measuredperiods as well as periods estimated from rotational velocities, wederive Rossby numbers (R_0_) for stars with B-V_o_>0.3 finding that awell-defined relationship between L_X_/L_bol_ and R_0_ is present bothfor early (i.e., F) and late-type stars. A comparison of the X-rayluminosity distribution functions (XLDF) for our α Per sample andthe Pleiades indicates that F and G-type stars in α Per are, as awhole, more X-ray luminous than their older counterparts in thePleiades. On the other hand, no significant difference is found betweenthe distributions of the K and M-type dwarfs in the two clusters. Weargue that this finding is a consequence of the longer spin-downtimescales of later-type objects, and hence of the fact that there aremore rapid rotators among G stars in α Per than in the Pleiades,while this is not the case for K and M dwarfs.
| 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.
| Seven-Color Photoelectric Photometry of Stars in the Alpha-Persei Open Cluster
Not Available
| Spectroscopic binaries in the Alpha Persei cluster
An average of 16 radial velocity measures for each of the 28 brightest(B3-A2) cluster members and found four binaries was obtained. Theresulting binary frequency of 14 percent is, like the previous 20percent for the B6-A1 stars in the Pleiades, unusually low compared witha typical 30 percent for early-type field stars or with 30 percent ormore in other open clusters. These two clusters are the only known oneswith unusually high mean rotational velocities. It is suspected that themean rotational velocities are high either because these clusters lackshort-period binaries or are not old enough for synchronization ofrotational and orbital velocities to have occurred. The four AlphaPersei binaries are all relatively wide ones (greater than 20 d) andwith small mass ratios (0.1-0.5). The same results apply to the youngOrion Nebula cluster. These results can be explained in terms of theformation of binaries by capture in that during the first free-falltime, capture will produce wide binaries with small mass ratios, as inthe Orion Nebula and Alpha Persei clusters, but repeated captures anddisruptions will produce more closely spaced binaries with many massratios near 1.0, as in IC 4665.
| Membership of low-mass stars in the open cluster Alpha Persei
The results of a combined astrometric, photometric, and spectroscopicsearch for low-mass members in the intermediate-age open cluster AlphaPersei are presented. Over 130 low-mass new members have been identifiedto M(v) about 12.5, almost doubling the previous number of knownmembers. The new membership information suggests a slight upwardrevision of Alpha Per's age to about 8 x 10 exp 7 yr. Alpha Per isnoticeably spatially elongated in a direction parallel to the Galacticplane, most likely due to tidal deformation. Analysis of thedistribution of relative H-alpha emission strengths among Alpha Permembers confirms the view that the mean H-alpha strength decreases inincreasingly older systems. Allowing for survey incompleteness, onecannot reject the idea that the luminosity function is consistent withthe field luminosity function to M(v) about 9 or 10.
| The measurement of precise radial velocities of early type stars
Methods are discussed which have made it possible to measure radialvelocities to within 1-3 km/s for O, B, and A spectral-type stars of allv sin i. The methods are based on the premise that neither the spectraltype nor the rotation velocity of a star need be well known prior to thevelocity measurement. This makes them particularly suitable for surveystudies or programs dealing with very heterogeneous samples of earlystars. Observations of early type members of the Pleiades and AlphaPersei open clusters at 3787 A shown that the radial-velocity zero pointused here for the early type stars is consistent with that for late-typestars to about 1 km/s for all spectral types and projected rotationvelocities.
| Starbursts, binary stars, and blue stragglers in local superclusters and groups. I - The very young disk and young disk populations
The distributions in the HR diagram with theoretical time-constant locifor stars in several young clusters and superclusters are compared todemonstrate that 'blue stragglers' in these aggregates are mostfrequently simply single massive (mode B) stars formed in bursts of starformation that occur at discrete intervals in time following theformation of the bulk of the low-mass (mode A) stars in the aggregate.The characteristics of the close binary systems in these aggregates areexamined to show that, in several cases, mass transfer by Roche lobeoverflow has or will occur and that, in some instances, the system wouldhave appeared as a blue straggler prior to the mass-transfer event, and,in other instances, mass transfer will lead to the identification of thesystem as a blue straggler. Thus, it is concluded that the bluestraggler phenomenon has at least two distinct physical origins: it mayoriginate from delayed formation (starbursts) or from 'delayedevolution' in some close binaries (mass transfer from an evolvedprimary).
| Effects of rotation on the colours and line indices of stars. I - The Alpha Persei Cluster
Analysis of the available observational data for the Alpha-Perseicluster members shows that rotation effects on the intermediate-bandindices c1 and (u-b) are considerable. In c1, rotation produces areddening of 0.040 magnitudes per 100 km/s. In (u-b), the effect for Bstars is found to be 0.06 magnitudes per 100 km/s of V sin i. Thebinaries and peculiar stars are found to behave differently in the colorexcess (due to rotation) versus V sin i diagrams. These empiricaleffects can be utilized to recalibrate these color indices and also toseparate members that are either chemically peculiar or in binarysystems.
| Photoelectric search for CP2-stars in open clusters. XII - Alpha Persei, Praesepe and NGC 7243
Observations of 95 stars in the open clusters Alpha Persei, Praesepe,and NGC 7243 have been performed by Delta-a photometry in order tosearch for the presence of the 5200-A feature of CP2 (or CP4) stars.Although peculiarity has been claimed for half a dozen stars in AlphaPersei, the photometry detects only the CP4 star (= He-weak) HL 985among the cluster members. The behavior of 3 Be/shell stars (HL 861,1164, 904) concerning the 5200-A feature is discussed. Praesepe, by farthe oldest cluster in the survey program, presents a very new andspecial case: 3 stars, previously classified as Am have Delta-a valuesaround 0.020 mag, i.e., they exhibit photometric peculiarity likeCP2-stars. Such values are incompatible with preceding results for fieldand cluster Am-stars (= CP3). These objects deserve further attentionboth photometrically and spectroscopically. NGC 7243 exhibits anoutstanding high frequency of CP2-stars; two certain Delta a-peculiarstars have been found: L 370, already known as peculiar, and the newlyidentified L 114. Two stars are near the detection level: L 58 and 121.According to Geneva photometry, L 487 is markedly peculiar.
| Radial velocity measurements. II - Ground-based observations of the program stars for the HIPPARCOS satellite
New radial velocities for 446 stars of magnitude 9.0 or brighter in 1616-sq-deg fields of the Northern Hemisphere are determined by automaticPDS measurement of 80-A/mm-dispersion spectra obtained at theObservatoire de Haute Provence using a 17-cm-diameter objective prism.The fields were selected to provide data for the input catalog of theESA Hipparcos astrometric satellite. The measurement techniques andprecision are discussed, and the results are presented in extensivetables and graphs.
| Picture gallery - A structured presentation of OAO-2 photometric data supported by OAO-2 spectrophotometric data and UBV, ANS and TD1 observations
Graphs are presented for the stellar fluxes of 531 stars in the5500-1330 A wavelength range, which have been divided into 52 categorieson the basis of spectral types. The merging of medium band interferencefilter photometry, UBV photometry, ANS photometry and TD1 fluxes, aswell as the ordering of the objects, should prove helpful in studies ofinterstellar reddening, luminosity effects, bandwidth effects, andcomparisons with model stellar atmospheres. The agreement between thevarious UV photometric systems for early-type stars is generally betterthan 0.10 mag. A list of stars whose photometric properties indicatestellar or interstellar anomalies is also provided.
| Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXIV - Filter photometry of 531 stars of diverse types
Ultraviolet magnitudes for 531 stars observed with the WisconsinExperiment Package on OAO 2 are tabulated. It is noted that these dataconstitute a subset of the OAO 2 data on file at the National SpaceScience Data Center. The tabulation contains previously published dataall reduced to a uniform magnitude system. It is pointed out that theobservations were obtained with the medium band interference filterphotometers. Eleven magnitudes are given designated by their centroidwavelengths.
| Apparent radii and other parameters for 416 B5 V-F5 V stars of the catalogue of the Geneva Observatory
Apparent radius, visual brightness, effective temperature and absoluteradius for 416 B5 v-F5 v stars of the catalogue of the GenevaObservatory (Rufener, 1976) have been determined. Twenty-eight stars,anomalous in log a" versus (m~)o diagrams, have been singled out. A goodcorrelation for seven stars, in common with the list of Hanbury Brown etal. (1974), has been found. Similar parameters determined for 279 B5v-F5 v stars of two preceding papers (Fracassini et al., 1973, 1975)have allowed us to determine the averaged diagrams , and versus (B -V)0 for 695 B5 v-F5 v stars. Moreover, in the present paper a goodcorrelation versus and carefulrelation = -7.40 + 3.31 for B5v-F5 V stars have been determined. Plain correlations between log R/R0and blanketing parameter m2 for some spectral types seem to point outthat there are real differences in the absolute radii of stars of thesame spectral type, in agreement with recent researches on the HRdiagram (Houck and Fesen, 1978). Systematic differences between double(spectroscopic and visual) and single stars are found. In particular,the averaged relation versus shows that A2v-F5 v double stars may have a higher metallicity index m2 and smallerabsolute radii than single stars. Finally, the diagram log v sin iversus log R/R0 confirms some properties of binary systems found byother researchers (Huang, 1966; Plavec, 1970; Levato, 1974; Kitamura andKondo, 1978)
| Spectral types in the alf Per cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90..692A&db_key=AST
| OAO 2 observations of the Alpha Persei cluster
UV photometry of the Alpha Persei cluster obtained with the OAO 2satellite is analyzed. The data are used together with ground-basedcoude spectra to examine 20 stars ranging in spectral type from B3 to A3for rotation effects as predicted by the models of Collins (1974) and ofCollins and Sonneborn (1977). Values of v sin i are estimated on therecalibrated system of Slettebak et al. (1975), and an H-R diagram isplotted for the program stars. The distribution of the stars on thediagram is compared with the ZAMS for a chemical composition of X = 0.7and Y = 0.02 as well as with two isochrones for logarithmic nuclear ages(in years) of 7.5 and 7.7. It is found that there is a seemingly narrowband of early-type stars lying a magnitude or so above the ZAMS on theplot, while the later types form a looser collection straddling theZAMS. The data for Alpha Persei itself yield an upper limit of 7.4 tothe logarithmic age. The analysis for rotation effects reveals onelate-type star that does not conform to the model predictions and one'weak helium' star. Evidence is discussed that these stars are notpole-on rapid rotators. It is concluded that there is a photometriceffect for stars earlier than about B6 whereby these stars are displacedredward in color-magnitude diagrams.
| Emission-line effects in H alpha, H beta, H gamma and UVBY photometry for B-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87..115C&db_key=AST
| Rotational velocities in the ORI association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79.1073S&db_key=AST
| Four-color and H beta photometry for open clusters. 10. The alf Per cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..687C&db_key=AST
| Blue CN-absorption measurements of close binary stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79...34K&db_key=AST
| La classification stellaire BCD : parametre caracteristique DU type spectral calibration EN magnitudes absolues.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&A....23...69C&db_key=AST
| NGC 2516 and the Pleiades Group
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...173...63E&db_key=AST
| The H-R diagram of the alf Per cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..242M&db_key=AST
| The radial velocities., luminosities of 77 stars in the field of the alf Per cluster.
Not Available
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