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Astrometry with the Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator δ Cephei
We present an absolute parallax and relative proper motion for thefundamental distance scale calibrator δ Cep. We obtain these withastrometric data from FGS 3, a white-light interferometer on the HubbleSpace Telescope (HST). Utilizing spectrophotometric estimates of theabsolute parallaxes of our astrometric reference stars and constrainingδ Cep and reference star HD 213307 to belong to the sameassociation (Cep OB6), we find πabs=3.66+/-0.15 mas. Thelarger than typical astrometric residuals for the nearby astrometricreference star HD 213307 are found to satisfy Keplerian motion withP=1.07 +/- 0.02 yr, a perturbation and period that could be due to an F0V companion ~7 mas distant from and ~4 mag fainter than the primary.Spectral classifications and VRIJHKT2M and DDO51 photometryof the astrometric reference frame surrounding δ Cep indicate thatfield extinction is high and variable along this line of sight. Howeverthe extinction suffered by the reference star nearest (in angularseparation and distance) to δ Cep, HD 213307, is lower and nearlythe same as for δ Cep. Correcting for color differences, we find=0.23+/-0.03 for δ Cep and hence an absolutemagnitude MV=-3.47+/-0.10. Adopting an average V magnitude,=15.03+/-0.03, for Cepheids with logP=0.73 in the largeMagellanic Cloud (LMC) from Udalski et al., we find a V-band distancemodulus for the LMC, m-M=18.50+/-0.13, or 18.58+/-0.15, where the lattervalue results from a highly uncertain metallicity correction. Theseagree with our previous RR Lyr HST parallax-based determination of thedistance modulus of the LMC. Based on observations made with theNASA/ESA Hubble Space Telescope, obtained at the Space Telescope ScienceInstitute, which is operated by the Association of Universities forResearch in Astronomy, Inc., under NASA contract NAS 5-26555.
| A Second Catalog of Orbiting Astronomical Observatory 2 Filter Photometry: Ultraviolet Photometry of 614 Stars
Ultraviolet photometry from the Wisconsin Experiment Package on theOrbiting Astronomical Observatory 2 (OAO 2) is presented for 614 stars.Previously unpublished magnitudes from 12 filter bandpasses withwavelengths ranging from 1330 to 4250 Å have been placed on thewhite dwarf model atmosphere absolute flux scale. The fluxes wereconverted to magnitudes using V=0 for F(V)=3.46x10^-9 ergs cm^-2 s^-1Å^-1, or m_lambda=-2.5logF_lambda-21.15. This second catalogeffectively doubles the amount of OAO 2 photometry available in theliterature and includes many objects too bright to be observed withmodern space observatories.
| A HIPPARCOS Census of the Nearby OB Associations
A comprehensive census of the stellar content of the OB associationswithin 1 kpc from the Sun is presented, based on Hipparcos positions,proper motions, and parallaxes. It is a key part of a long-term projectto study the formation, structure, and evolution of nearby young stellargroups and related star-forming regions. OB associations are unbound``moving groups,'' which can be detected kinematically because of theirsmall internal velocity dispersion. The nearby associations have a largeextent on the sky, which traditionally has limited astrometricmembership determination to bright stars (V<~6 mag), with spectraltypes earlier than ~B5. The Hipparcos measurements allow a majorimprovement in this situation. Moving groups are identified in theHipparcos Catalog by combining de Bruijne's refurbished convergent pointmethod with the ``Spaghetti method'' of Hoogerwerf & Aguilar.Astrometric members are listed for 12 young stellar groups, out to adistance of ~650 pc. These are the three subgroups Upper Scorpius, UpperCentaurus Lupus, and Lower Centaurus Crux of Sco OB2, as well as VelOB2, Tr 10, Col 121, Per OB2, alpha Persei (Per OB3), Cas-Tau, Lac OB1,Cep OB2, and a new group in Cepheus, designated as Cep OB6. Theselection procedure corrects the list of previously known astrometricand photometric B- and A-type members in these groups and identifiesmany new members, including a significant number of F stars, as well asevolved stars, e.g., the Wolf-Rayet stars gamma^2 Vel (WR 11) in Vel OB2and EZ CMa (WR 6) in Col 121, and the classical Cepheid delta Cep in CepOB6. Membership probabilities are given for all selected stars. MonteCarlo simulations are used to estimate the expected number of interloperfield stars. In the nearest associations, notably in Sco OB2, thelater-type members include T Tauri objects and other stars in the finalpre-main-sequence phase. This provides a firm link between the classicalhigh-mass stellar content and ongoing low-mass star formation. Detailedstudies of these 12 groups, and their relation to the surroundinginterstellar medium, will be presented elsewhere. Astrometric evidencefor moving groups in the fields of R CrA, CMa OB1, Mon OB1, Ori OB1, CamOB1, Cep OB3, Cep OB4, Cyg OB4, Cyg OB7, and Sct OB2, is inconclusive.OB associations do exist in many of these regions, but they are eitherat distances beyond ~500 pc where the Hipparcos parallaxes are oflimited use, or they have unfavorable kinematics, so that the groupproper motion does not distinguish it from the field stars in theGalactic disk. The mean distances of the well-established groups aresystematically smaller than the pre-Hipparcos photometric estimates.While part of this may be caused by the improved membership lists, arecalibration of the upper main sequence in the Hertzsprung-Russelldiagram may be called for. The mean motions display a systematicpattern, which is discussed in relation to the Gould Belt. Six of the 12detected moving groups do not appear in the classical list of nearby OBassociations. This is sometimes caused by the absence of O stars, but inother cases a previously known open cluster turns out to be (part of) anextended OB association. The number of unbound young stellar groups inthe solar neighborhood may be significantly larger than thoughtpreviously.
| A Search for Star Clusters from the HIPPARCOS Data
We present results of a search for nearby star clusters and associationsusing Hipparcos Catalogue data, restricting the sample to stars withparallaxes above 2 mas (d <~ 500 pc). Two new OB associations havebeen identified in the Carina-Vela and Cepheus-Cygnus-Lyra-Vulpecularegions. A very probable new open cluster has been discovered in Carina.The cluster, a Car, named after its brightest member, is young (60 Myr)and nearby (d = 132 pc). However, only seven bona fide members can bedrawn from the Hipparcos data. We report a detection of nine opencluster candidates in the distance range of 150 to 400 pc, and sixpossible associations almost all located within the Gould belt, althoughslightly older than the known nearby associations. In all cases, wepresent Yale theoretical isochrone fits to the color-magnitude diagrams,which indicate a moderate spread of ages between 60 to 200 Myr.Evidently, these young open cluster and association candidates arerelated to the overall distribution of young OB and A-type stars in thesolar neighborhood.
| 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
| 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.
| Atmospheric Motions in Classical Cepheid Stars - Part One - the Star of Reference - Delta-Cephei
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...277..524B&db_key=AST
| 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.
| A catalog of ultraviolet interstellar extinction excesses for 1415 stars
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
| 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.
| Erratum - Errors or Omissions in Star-Identifications in the General Catalogue of Trigonometric Stellar Parallaxes
Not Available
| Outer atmospheres of cool stars. II - MG II flux profiles and chromospheric radiative loss rates
International Ultraviolet Explorer high-resolution spectra of the Mg IIlines at 2796, 2803 A in 15 stars of spectral type G2-M2 including awide range of luminosities are presented. These spectra are calibratedin absolute flux units at earth and at the stellar surface, and thechromospheric radiative loss rates in the Mg II lines are compared withcorresponding rates in the Ca II H, K, and 8542 lines. The ratio of MgII surface flux to total surface flux is found to be independent ofstellar luminosity and thus gravity; may decrease slowly with decreasingeffective temperature, and increases with decreasing period among RSCanum Venaticorum binaries. The factor of 10 range in this ratio at eacheffective temperature may be due to differences in the fractionalsurface area covered by plages and may indicate that stars of allluminosity classes have chromospheric plages. In this small data sampleno evidence is found that the Mg II line surface fluxes indicate whethera star possesses a transition region and hot corona.
| A Copernicus survey of MG II emission in late-type stars
The behavior of Mg II emission in late-type stars is examined using scandata obtained with the Copernicus satellite. The luminosity in the Mg IIk emission line was found to be closely related to stellar absolutemagnitude, leading to the suggestion that such correlation may be veryuseful for future UV observations. The stellar surface flux in the kline was observed to be roughly constant or to decrease slowly withlater spectral type, a finding which is then used to show that thepressure at the top of the chromosphere decreases with later spectraltype, in agreement with the conclusions by McClintock et al. (1975). Anasymmetry in the Mg II k line was noticed to be present in the availabledata for the stars later than K2-K5.
| Interstellar reddening of del Cep.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976PASP...88..709F&db_key=AST
| Estimation of the parameters of galactic rotation and solar motion with respect to population I cepheids.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&A.....9..410C&db_key=AST
| A simple model for cepheid variability.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&A.....6..193R&db_key=AST
| On the distance scale of the nearby classical cepheids.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&A.....6..130J&db_key=AST
| The Zero-Point of the Period-Luminosity-Relation of Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&A.....5..116G&db_key=AST
| Intermediate and narrow band photometry of cepheids.
Not Available
| Interstellar Matter in the Region of the Perseus II Association
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969PASP...81..496L&db_key=AST
| The Blue Companion of Delta Cephei (δ Cep C).
Not Available
| Classification de cepheides. I. Determination de rougissements.
Not Available
| A catalogue of fundamental data for classical cepheids in the galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..492F&db_key=AST
| Atmospheric Parameters for RU Cam during its Recent Quiescent Phase
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...151.1011W&db_key=AST
| A Composite Period-Luminosity Relation for Cepheids at Mean and Maximum Light
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...151..531S&db_key=AST
| Photoelectric K-line spectral classification.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73...14L&db_key=AST
| Observational Evidence for Overtone Pulsations in Classical Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...151..197F&db_key=AST
| The frequency of Cepheid binaries
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968MNRAS.141..109L&db_key=AST
| The atmosphere of the long period cepheid 1 Carinae-I. Curve of growth analysis and hydrogen line profiles
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968MNRAS.138...23R&db_key=AST
| Observational studies relating to star formation. I.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967AJ.....72.1019A&db_key=AST
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Miembro de los siguientes grupos:
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Datos observacionales y astrométricos
| Constelación: | Cefeo |
| Ascensión Recta: | 22h29m09.24s |
| Declinación: | +58°24'14.8" |
| Magnitud Aparente: | 6.108 |
| Distancia: | 291.545 parsecs |
| Movimiento Propio en Ascensión Recta: | 16.9 |
| Movimiento Propio en Declinación: | 4.2 |
| B-T magnitude: | 6.177 |
| V-T magnitude: | 6.114 |
Catálogos y designaciones:
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