A Hipparcos study of the Hyades open cluster. Improved colour-absolute magnitude and Hertzsprung-Russell diagrams

Hipparcos parallaxes x distances to individual stars in the Hyades cluster with an accuracy of 6p er- cent. We use the Hipparcos proper motions, which have a larger relative precision than the trigonometric paral- laxes, to derive 3 times more precise distance estimates, by assuming that all members share the same space motion. An investigation of the available kinematic data conrms that the Hyades velocity eld does not contain signicant structure in the form of rotation and/or shear, but is fully consistent with a common space motion plus a (one-dimensional) internal velocity dispersion of 0.30 km s 1 . The improved parallaxes as a set are statistically consistent with the Hipparcos parallaxes. The maximum expected systematic error in the proper motion-based parallaxes for stars in the outer regions of the cluster (i.e., beyond 2 tidal radii 20 pc) is < 0.30 mas. The new parallaxes conrm that the Hipparcos measurements are correlated on small angular scales, consistent with the limits specied in the Hipparcos Catalogue, though with signicantly smaller \amplitudes" than claimed by Narayanan & Gould. We use the Tycho{2 long time-baseline astrometric catalogue to derive a set of independent proper motion-based parallaxes for the Hipparcos members. The new parallaxes provide a uniquely sharp view of the three-dimensional structure of the Hyades. The colour-absolute magnitude diagram of the cluster based on the new parallaxes shows a well-dened main sequence with two \gaps"/\turn-os". These features provide the rst direct observational support of Bohm{Vitense's prediction that (the onset of) surface convection in stars signicantly aects their (B V ) colours. We present and discuss the theoretical Hertzsprung{Russell diagram (log L versus log Te) for an objectively dened set of 88 high-delity members of the cluster as well as the Scuti star 2 Tau, the giants 1 , 1 , ,a nd Tau, and the white dwarfs V471 Tau and HD 27483 (all of which are also members). The precision with which the new parallaxes place individual Hyades in the Hertzsprung{Russell diagram is limited by (systematic) uncertainties related to the transformations from observed colours and abso- lute magnitudes to eective temperatures and luminosities. The new parallaxes provide stringent constraints on the calibration of such transformations when combined with detailed theoretical stellar evolutionary modelling, tailored to the chemical composition and age of the Hyades, over the large stellar mass range of the cluster probed by Hipparcos.

[1]  Italy.,et al.  Stellar models and Hyades: the Hipparcos test , 2000, astro-ph/0009019.

[2]  P. T. de Zeeuw,et al.  Two Böhm-Vitense Gaps in the Main Sequence of the Hyades , 2000, astro-ph/0011162.

[3]  Jean Kovalevsky,et al.  Astronomical Applications of Astrometry: The Hipparcos and Tycho Catalogues , 2008 .

[4]  T. Simon,et al.  71 Tauri: Hyades Enigma Resolved? , 2000 .

[5]  G. Meynet,et al.  THE EVOLUTION OF ROTATING STARS , 2000, astro-ph/0004204.

[6]  Y. Lebreton.  Stellar Structure and Evolution: Deductions from Hipparcos , 2000, astro-ph/0003351.

[7]  D. Alves.  K-Band Calibration of the Red Clump Luminosity , 2000, astro-ph/0003329.

[8]  R. Hoogerwerf.  OB association members in the ACT and TRC catalogues , 2000 .

[9]  B. Rachford,et al.  The Relationship Between the Böhm-Vitense Gap and Stellar Activity in Open Clusters , 2000 .

[10]  J. Richer,et al.  The Evolution of AmFm Stars, Abundance Anomalies, and Turbulent Transport , 2000 .

[11]  L. Girardi,et al.  Evolutionary tracks and isochrones for low- and intermediate-mass stars: From 0.15 to 7 , and from to 0.03 , 1999, astro-ph/9910164.

[12]  A. Udalski,et al.  The Optical Gravitational Lensing Experiment: Red Clump Stars as a Distance Indicator , 1999, The Astrophysical journal.

[13]  De Bruijne,et al.  Structure and colour-magnitude diagrams of Scorpius OB2 based on kinematic modelling of Hipparcos data , 1999 .

[14]  Johns Hopkins University,et al.  Improved Color-Temperature Relations and Bolometric Corrections for Cool Stars , 1999, astro-ph/9911367.

[15]  S. Udry,et al.  A catalog of rotational and radial velocities for evolved stars - V. Southern stars , 2013, 1312.3474.

[16]  S. Roser,et al.  Construction of the Tycho Reference Catalogue , 1999 .

[17]  J. Bruijne.  A refurbished convergent-point method for finding moving groups in the Hipparcos Catalogue★ , 1999, astro-ph/9903239.

[18]  Leiden,et al.  Identification of moving groups and member selection using Hipparcos data , 1999, astro-ph/9903240.

[19]  B. J. Taylor.  Catalogs of temperatures and [Fe/H] averages for evolved G and K stars , 1999 .

[20]  V. Narayanan,et al.  Correlated Errors in Hipparcos Parallaxes toward the Pleiades and the Hyades , 1998, astro-ph/9810328.

[21]  Daniel Egret,et al.  Harmonizing Cosmic Distance Scales in a Post‐Hipparcos Era , 1999 .

[22]  W. Voges,et al.  The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars , 1998 .

[23]  B. Rachford.  Chromospheric Activity in the Late A- and Early F-Type Stars of Open Clusters. I. Hyades, Praesepe, and Coma , 1998 .

[24]  V. Narayanan,et al.  A Precision Test of Hipparcos Systematics toward the Hyades , 1998, astro-ph/9808284.

[25]  F. Allard,et al.  The NextGen Model Atmosphere Grid for 3000 ≤ Teff ≤ 10,000 K , 1998, astro-ph/9807286.

[26]  M. Burleigh,et al.  A search for hidden white dwarfs in the ROSAT EUV survey - II. Discovery of a distant DA+F6/7V binary system in a direction of low-density neutral hydrogen , 1998, astro-ph/9806269.

[27]  Cea,et al.  Standard Solar Models in the Light of New Helioseismic Constraints. I. The Solar Core , 1998, astro-ph/9806272.

[28]  Thomas E. Corbin,et al.  The ACT Reference Catalog , 1998 .

[29]  M. Pinsonneault,et al.  The Problem of Hipparcos Distances to Open Clusters. I. Constraints from Multicolor Main-Sequence Fitting , 1998, astro-ph/9803233.

[30]  G. L. Wycoff,et al.  The AC 2000: The Astrographic Catalogue on the System Defined by the Hipparcos Catalogue , 1998 .

[31]  B. Yanny,et al.  An Absence of Gaps in the Main-Sequence Population of Field Stars , 1998, astro-ph/9802204.

[32]  I. Reid,et al.  The Multiplicity of the Hyades and Its Implications for Binary Star Formation and Evolution , 1998, astro-ph/9801216.

[33]  B.E.J. PagelL. Portinari.  Δ Y/Δ Z from fine structure in the main sequence based on Hipparcos parallaxes , 1997, astro-ph/9711332.

[34]  France.,et al.  A standard stellar library for evolutionary synthesis - II. The M dwarf extension , 1997, astro-ph/9710350.

[35]  A. E. Lynas-Gray,et al.  Determination of the temperatures of selected ISO flux calibration stars using the Infrared Flux Method , 1997 .

[36]  Martin A. Barstow,et al.  The mass, temperature and distance of the white dwarf in V471 Tauri , 1997 .

[37]  B. Rachford.  Chromospheric Activity in Dwarf and Evolved Late A- and Early F-Type Stars , 1997 .

[38]  P. Morel.  CESAM: A code for stellar evolution calculations , 1997 .

[39]  D. Latham,et al.  The Hyades Binaries θ1 Tauri and θ2 Tauri: The Distance to the Cluster and the Mass-Luminosity Relation , 1997 .

[40]  H. Eichhorn,et al.  A New and Comprehensive Determination of the Distance to Member Stars of the Hyades , 1997 .

[41]  D. Latham,et al.  The Hyades Binary Finsen 342 (70 Tauri): A Double-lined Spectroscopic Orbit, the Distance to the Cluster, and the Mass-Luminosity Relation , 1997 .

[42]  W. Landsman,et al.  Convection, Thermal Bifurcation, and the Colors of A Stars , 1997, astro-ph/9702112.

[43]  M. Pinsonneault,et al.  Rotational Velocities and Chromospheric Activity of M Dwarfs in the Hyades , 1997 .

[44]  D. Latham,et al.  The Hyades Binary 51 Tauri: Spectroscopic Detection of the Primary, the Distance to the Cluster, and the Mass-Luminosity Relation , 1997 .

[45]  P. Flower,et al.  Transformations from Theoretical Hertzsprung-Russell Diagrams to Color-Magnitude Diagrams: Effective Temperatures, B-V Colors, and Bolometric Corrections , 1996 .

[46]  V. Canuto,et al.  Stellar Turbulent Convection: A Self-consistent Model , 1996, astro-ph/9609001.

[47]  David A. H. Buckley,et al.  An EUV-selected sample of DA white dwarfs from the ROSAT All-Sky Survey — I. Optically derived stellar parameters , 1997 .

[48]  P. Kenneth Seidelmann,et al.  Astronomical and astrophysical objectives of sub-milliarcsecond optical astrometry : proceedings of the 166th Symposium of the International Astronomical Union, held in the Hague, the Netherlands, August 15-19, 1994 , 1995 .

[49]  E. Böhm-Vitense.  White Dwarf Companions to Hyades F Stars , 1995 .

[50]  N. Morrell,et al.  The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars , 1995 .

[51]  S. Balachandran.  The Lithium Dip in M67: Comparison with the Hyades, Praesepe, and NGC 752 Clusters , 1995 .

[52]  J. Nousek,et al.  Photospheric, circumstellar, and interstellar features of HE, C, N. O, and Si in the HST spectra of four hot white dwarf stars , 1995 .

[53]  Xiaopei Pan,et al.  Spectroscopic detection of the secondaries of the Hyades interferometric spectroscopic binary theta(sup 2) Tauri and of the interferometric spectroscopic binary alpha Andromedae , 1995 .

[54]  M. Pinsonneault,et al.  Stellar models with microscopic diffusion and rotational mixing 2.: Application to open clusters , 1994, astro-ph/9408059.

[55]  E. D. Hoffleit,et al.  The general catalogue of trigonometric [stellar] parallaxes , 1995 .

[56]  Y. Lebreton,et al.  Accurate Parallaxes and Stellar Ages Determinations , 1995 .

[57]  D. Koester,et al.  White dwarfs : proceedings of the 9th European Workshop on White Dwarfs held at Kiel, Germany, 29 August - 1 September 1994 , 1995 .

[58]  John R. Stauffer,et al.  Coronal X-ray sources in the Hyades: A 40 kilosecond ROSAT pointing , 1994 .

[59]  F. Rogers,et al.  The Hyades lithium problem revisited , 1994 .

[60]  Neill Reid,et al.  Low-mass stars in the Hyades , 1993 .

[61]  E. Boehm-Vitense.  Detection of a white dwarf companion to the Hyades stars HD 27483 , 1993 .

[62]  O. Eggen.  Degenerate stars in the Hyades supercluster , 1993 .

[63]  D. Peterson,et al.  The spectroscopic orbit of Theta2 Tauri , 1993 .

[64]  Brian D. Mason,et al.  ICCD speckle observations of binary stars. VII: a duplicity survey of the Hyades cluster , 1993 .

[65]  Michel Casse,et al.  Origin and evolution of the elements , 1993 .

[66]  S. Hodgkin,et al.  First Results from ROSAT All-Sky Survey Observations of the Hyades Cluster , 1992 .

[67]  S. Casertano,et al.  White dwarfs in the halo of the Hyades Cluster - The case of the missing white dwarfs , 1992 .

[68]  O. Eggen.  The Hyades supercluster in the FK5 , 1992 .

[69]  G. Gatewood,et al.  Map-based trigonometric parallaxes of open clusters. II - The Hyades: 51 Tauri , 1992 .

[70]  B. N. Ashoka,et al.  WHOLE EARTH TELESCOPE OBSERVATIONS OF V471 TAURI - THE NATURE OF THE WHITE-DWARF VARIATIONS , 1992 .

[71]  I. Mazzitelli,et al.  Further improvements of a new model for turbulent convection in stars , 1992 .

[72]  A. Harris,et al.  Rosat sky survey observations of the eclipsing binary V471 Tauri , 1992 .

[73]  T. Mazeh,et al.  Spectroscopic searches for low-mass companions of stars , 1992 .

[74]  M. Shao,et al.  Sub-Milliarcsecond Binary Star Astrometry , 1992 .

[75]  M. Giampapa,et al.  The Chromospheric Activity of Low-Mass Stars in the Hyades , 1991 .

[76]  I. Mazzitelli,et al.  Stellar Turbulent Convection: A New Model and Applications , 1991 .

[77]  K. Janes.  The formation and evolution of star clusters , 1991 .

[78]  Andrew McWilliam,et al.  High-resolution spectroscopic survey of 671 GK giants. I. Stellar atmosphere parameters and abundances , 1990 .

[79]  E. Friel,et al.  Chemical composition of open clusters. I. Fe/H from high-resolution spectroscopy. II. C/H and C/Fe in F dwarfs from high-resolution spectroscopy , 1990 .

[80]  A. Dobson.  ACTIVITY, METALLICITY, HELIUM, AND THE HYADES ANOMALY , 1990 .

[81]  Achim Weiss,et al.  Stellar Structure and Evolution , 1990 .

[82]  A. Boesgaard.  Metallicity in Galactic Clusters from High Signal-to-Noise Spectroscopy , 1989 .

[83]  L. Motz,et al.  The Structure and Evolution of Stars , 1989 .

[84]  J. Gunn,et al.  A new convergent point and distance modulus for the Hyades from radial velocities , 1988 .

[85]  H. Lanning,et al.  Spectroscopy of V471 Tau. I. Review of basic properties , 1988 .

[86]  A. Renzini,et al.  Tests of evolutionary sequences using color-magnitude diagrams of globular clusters , 1988 .

[87]  J.-C. Mermilliod,et al.  The Hipparcos input catalogue , 1987 .

[88]  D. Peterson,et al.  Finsen 342 and the Hyades distance modulus , 1987 .

[89]  E. Terlevich.  Evolution of N-body open clusters , 1987 .

[90]  L. Hartmann,et al.  Rotation and Magnetic Activity in Main-Sequence Stars , 1987 .

[91]  T. Simon,et al.  Activity in F stars , 1986 .

[92]  E. Guinan,et al.  EXOSAT observations of V471 Tauri - a 9. 25 minute white dwarf pulsation and orbital phase dependent X-ray dips , 1986 .

[93]  A. Boesgaard,et al.  Lithium in the Hyades Cluster , 1986 .

[94]  G. Michaud.  The lithium abundance gap in the Hyades F stars - The signature of diffusion , 1986 .

[95]  H. Abt.  The spectra and ages of blue stragglers , 1985 .

[96]  Robert C. Smith,et al.  The photometric effect of rotation in the A stars , 1985 .

[97]  E. Guinan,et al.  IUE spectroscopy of the degenerate components in the Hyades close binaries V471 Tauri and HZ9 , 1984 .

[98]  B. Campbell.  Color anomalies and starspots in Hyades dwarfs. , 1984 .

[99]  R. Radick,et al.  Radial velocity of the Hyades cluster , 1984 .

[100]  T. Bridges,et al.  Theoretical zero-age main sequences applied to the Pleiades, Praesepe,and Hyades star clusters. , 1984 .

[101]  O. Eggen.  NGC 2423 and the red giants of the Hyades supercluster , 1983 .

[102]  Carlos Jaschek,et al.  The Bright Star Catalogue , 1982 .

[103]  E. Boehm-Vitense.  Effective temperatures of A and F stars. , 1982 .

[104]  R. Mcclure.  The Hyades binary HD 27130 and the mass-luminosity relation and distance of the Hyades cluster , 1982 .

[105]  E. H. Olsen,et al.  EVIDENCE OF HELIUM ABUNDANCE DIFFERENCES BETWEEN THE HYADES STARS AND FIELD STARS, AND BETWEEN HYADES STARS AND COMA CLUSTER STARS , 1982 .

[106]  E. Bohm-Vitense.  The Effective Temperature Scale , 1981 .

[107]  R. Baron,et al.  Lunar occultations of the Hyades. II - August 1980 , 1981 .

[108]  H. Lanning,et al.  HZ 9 : a white-dwarf-red-dwarf spectroscopic binary in the Hyades. , 1981 .

[109]  T. D. Angelov,et al.  On the structure and evolution of stars. I. , 1981 .

[110]  Carlos Jaschek,et al.  The classification of stars , 1987 .

[111]  D. Dearborn,et al.  Magnetic mixing and the Arcturus problem , 1980 .

[112]  F. Wesemael,et al.  Atmospheres for hot, high-gravity stars. I. Pure hydrogen models. , 1980 .

[113]  G. D. Nelson.  Granulation in a main-sequence F-type star , 1980 .

[114]  B. J. Taylor.  An investigation of previously derived Hyades, Coma, and M67 reddenings , 1980 .

[115]  S. T. Ridgway,et al.  Effective temperatures of late-type stars : the field giants from K0 to M6. , 1980 .

[116]  S. Bergh.  The distance to the Hyades Cluster and the extragalactic distance scale. , 1977 .

[117]  J. Gunn,et al.  Hyades giants delta and theta 1 Tauri as spectroscopic binaries. , 1977 .

[118]  A. Young.  Improved spectroscopic orbit for the white dwarf eclipsing binary BD+16degree516 , 1976 .

[119]  Arthur D. Code,et al.  Empirical effective temperatures and bolometric corrections for early-type stars , 1976 .

[120]  A. Gußmann.  B. BASCHEK, W. H. KEGEL, G. TRAVING (eds.) : Problems in Stellar Atmospheres and Envelopes. Springer‐Verlag, Berlin‐Heidelberg‐New‐York, 1975. XIX + 375 Seiten. Preis DM 48.‐ , 1976 .

[121]  D. Crawford.  Empirical calibration of the ubvy,beta systems. I. The F-type stars. , 1975 .

[122]  D. Reimers.  Circumstellar Envelopes and Mass Loss of Red Giant Stars , 1975 .

[123]  R. Hanson.  A study of the motion, membership, and distance of the Hyades cluster. , 1975 .

[124]  E. Bohm-Vitense,et al.  The gap in the two-color diagram of main-sequence stars , 1974 .

[125]  A. Young,et al.  Analysis of the White-Dwarf Eclipsing Binary BD+16°516 , 1972 .

[126]  R. Stothers,et al.  Low-mass white dwarfs and the cooling sequences in the Hyades cluster , 1971 .

[127]  A. Young,et al.  A NEW ECLIPSING BINARY CONTAINING A VERY HOT WHITE DWARF , 1970 .

[128]  E. Upton.  CALIBRATION OF THE HYADES--PRAESEPE MAIN SEQUENCE BY A NEW TREATMENT OF THE STELLAR MOTIONS. , 1970 .

[129]  Richard H. Miller,et al.  ON the Interpretation of the Color-Magnitude Diagrams of M67 and NGC 188 , 1969 .

[130]  John P. Cox,et al.  Principles of stellar structure , 1968 .

[131]  P. Wayman.  THE HYADES CLUSTER PARALLAX , 1967 .

[132]  J. Faulkner.  QUASI-HOMOLOGY RELATIONS AND THE EGGEN--SANDAGE RESIDUE. , 1967 .

[133]  G. Wallerstein,et al.  A SUGGESTED REVISION IN THE DISTANCE TO THE HYADES AND ITS IMPLICATIONS , 1966 .

[134]  R. P. Kraft,et al.  Studies of Stellar Rotation. II. The Effect of Rotation on the Colors and Magnitudes of A-And F-Type Stars in the Hyades. , 1965 .

[135]  Edwin E. Salpeter,et al.  MODELS FOR ZERO-TEMPERATURE STARS , 1961 .

[136]  S. Chandrasekhar.  Hydrodynamic and Hydromagnetic Stability , 1961 .

[137]  L. G. Henyey,et al.  A Method for Automatic Computation of Stellar Evolution. , 1959 .

[138]  F. Bertiau.  Absolute Magnitudes of Stars in the Scorpio-Centaurus Association. , 1958 .

[139]  H. W. Babcock.  Magnetic Fields of the A-Type Stars. , 1958 .

[140]  W. Luyten.  The search for faint blue stars. IV: More blue stars in the Hyades Region , 1956 .

[141]  W. Luyten.  A search for faint blue stars. II. The Hyades and the south galactic polar region , 1954 .

[142]  Archibald H. Brown.  On the Determination of the Convergent Point of a Moving Cluster from Proper Motions. , 1950 .

[143]  B. Strömgren.  Problems of stellar atmospheres. , 1948 .

[144]  F. Zwicky,et al.  A Search for Faint Blue Stars. , 1947 .

[145]  F. H. Seares.  Regression Lines and the Functional Relation. II. Charlier's Formulae for a Moving Cluster. , 1945 .

[146]  W. Smart.  The Scorpio-Centaurus cluster (the southern stream) , 1939 .

[147]  J. O’Connor.  The Taurus cluster , 1914 .

[148]  L. Boss.  Convergent of a moving cluster in Taurus , 1908 .