J/A+A/331/81 J/A+A/331/81 Hyades membership M A C Perryman A G A Brown Y Lebreton A Gomez C Turon G Cayrel de Strobel J C Mermilliod N Robichon J Kovalevsky F Crifo Astron. Astrophys. 331 81 1998 1998A&A...331...81P I/239 : The Hipparcos and Tycho Catalogues (ESA 1997) Clusters, open Parallaxes, trigonometric Radial velocities Stars, distances astrometry distance scale Hertzsprung-Russell (HR diagram) open clusters and associations: individual (Hyades) parallaxes We use absolute trigonometric parallaxes from the Hipparcos Catalogue (Cat. <I/239>) to determine individual distances to members of the Hyades cluster, from which the 3-dimensional structure of the cluster can be derived. Inertially-referenced proper motions are used to rediscuss distance determinations based on convergent-point analyses. A combination of parallaxes and proper motions from Hipparcos, and radial velocities from ground-based observations, are used to determine the position and velocity components of candidate members with respect to the cluster centre, providing new information on cluster membership: 13 new candidate members within 20pc of the cluster centre have been identified. Farther from the cluster centre there is a gradual merging between certain cluster members and field stars, both spatially and kinematically. Within the cluster, the kinematical structure is fully consistent with parallel space motion of the component stars with an internal velocity dispersion of about 0.3km/s. The spatial structure and mass segregation are consistent with N-body simulation results, without the need to invoke expansion, contraction, rotation, or other significant perturbations of the cluster. The quality of the individual distance determinations permits the cluster zero-age main sequence to be accurately modelled. The helium abundance for the cluster is determined to be Y=0.26+/-0.02 which, combined with isochrone modelling including convective overshooting, yields a cluster age of 625+/-50Myr. The distance to the observed centre of mass (a concept meaningful only in the restricted context of the cluster members contained in the Hipparcos Catalogue) is 46.34+/-0.27pc, corresponding to a distance modulus m-M=3.33+/-0.01mag for the objects within 10pc of the cluster centre (roughly corresponding to the tidal radius). This distance 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 trigonometric parallax determinations, and smaller than those found from recent studies of the cluster convergent point. These discrepancies are investigated and explained.

HIP Hipparcos Catalogue (HIP, Cat. <I/239>) number --- vB van Bueren number (1952BAN....11..385V) --- n_vB n: new candidate proposed in this paper --- MembvB Membership according to van Bueren number=1 Data on the membership of the Hyades for the 282 stars in our sample, listed by various authors. Membership or non-membership inferred by the relevant authors are indicated by `1' or `0' in the corresponding column respectively (see paper for details). --- vA van Altena number (1969AJ.....74....2V) --- n_vA n: new candidate proposed in this paper --- MembvA Membership according to van Altena number=1 Data on the membership of the Hyades for the 282 stars in our sample, listed by various authors. Membership or non-membership inferred by the relevant authors are indicated by `1' or `0' in the corresponding column respectively (see paper for details). --- Han Hanson number (1975, Cat. <J/AJ/80/379>) --- n_Han n: new candidate proposed in this paper --- MembHan Membership according to Hanson number=1 Data on the membership of the Hyades for the 282 stars in our sample, listed by various authors. Membership or non-membership inferred by the relevant authors are indicated by `1' or `0' in the corresponding column respectively (see paper for details). --- Pel Pels et al. (1975A&A....43..423P) (Leiden) number, van Bueren stars have the vB number + 1000 --- n_Pel n: new candidate proposed in this paper --- MembPel Membership according to Pels et al. number=1 Data on the membership of the Hyades for the 282 stars in our sample, listed by various authors. Membership or non-membership inferred by the relevant authors are indicated by `1' or `0' in the corresponding column respectively (see paper for details). --- Grif Sequential number in Table4 of Griffin et al. (1988AJ.....96..172G) --- n_Grif n: new candidate proposed in this paper --- MembGrif Membership according to Griffin et al. number=1 Data on the membership of the Hyades for the 282 stars in our sample, listed by various authors. Membership or non-membership inferred by the relevant authors are indicated by `1' or `0' in the corresponding column respectively (see paper for details). --- Scha Schwan number (1991A&A...243..386S) --- n_Scha n: new candidate proposed in this paper --- MembScha Membership according to Schwan number=1 Data on the membership of the Hyades for the 282 stars in our sample, listed by various authors. Membership or non-membership inferred by the relevant authors are indicated by `1' or `0' in the corresponding column respectively (see paper for details). --- plx Hipparcos parallax (milliarcsec=mas) mas e_plx Hipparcos parallax standard error mas RV Radial velocity km/s u_RV Uncertainty flag on RV --- n_RV # indicates SB/RV with undetermined gamma velocity --- e_RV Error in radial velocity km/s r_RV Source of radial velocity number=2 Sources of radial velocities: (0) Radial velocity unknown; (1) Griffin et al., 1988AJ.....96..172G 1985AJ.....90..609G 1981AJ.....86..588G 1978AJ.....83.1114G 1977AJ.....82..176G 1982A&A...106..221G (2) Hipparcos Input Catalogue, Cat. <I/196> (mainly from R.E. Wilson, 1953, Cat. <III/21>) (3) Weighted mean of ref. 2 (39.6+/-1.2) and Kraft, 1965ApJ...142..681K (38.4+/-1.5) (4) Kraft, 1965ApJ...142..681K (37.4+/-0.4 and 36.5+/-0.5) Cheriguene, 1971A&A....13..447C (37.3+/-0.7) (5) McClure, 1982ApJ...254..606M (6) Torres et al., 1997ApJ...474..256T (7) Mayor & Mazeh, 1987A&A...171..157M (8) Kraft, 1965ApJ...142..681K (9) Margoni et al., 1992A&AS...93..545M (10) Lucy & Sweeney, 1971AJ.....76..544L (11) Abt & Levy, 1985ApJS...59..229A (12) Griffin, 1971MNRAS.155....1G (13) Andersen & Nordstrom, 1983A&A...122...23A (14) Morse et al., 1991AJ....101.1495M (15) Detweiler et al., 1984AJ.....89.1038D (16) Weighted mean of data from Palmer et al., 1968RGOB..135..385P and Stillwell, 1948PDAO....7..337S (17) Tomkin et al., 1995AJ....109..780T (18) Heintz, 1981ApJS...46..247H (19) Abt, 1965ApJS...11..429A (20) Fekel, 1980PASP...92..785F (21) Perraud, 1962JO.....45..361P (22) Fouts & Sandage, 1986AJ.....91.1189F, Cat. <III/144> (star G83-18) (23) Strassmeier et al., 1988A&AS...72..291S, See Cat. <V/76> (24) New Coravel observations provided by J.C. Mermilliod (25) Woolley et al., 1971ROAn...14....1W (26) Hanson & Vasilevskis, 1983AJ.....88..844H (27) Evans, 1978BICDS..15..121E (28) Orbit recomputed by Mermilliod with period=490+/-1d (from Batten) --- Note SB: spectroscopic binary, RV: radial velocity (possibly) variable --- Note2 Historical status flag number=3 Star was previously known, or classified by Hipparcos, to have resolved components (from Field H56, Cat. <I/239>); this may overlap with the flag in the next column, but may also indicate visual or wide binary (see paper for details) H : determined multiple by Hipparcos, previously unknown I : system previously identified as multiple in HIC <I/196> (annex1) M : miscellaneous (system identified after publication of HIC) --- Note3 Double/Multiple Systems flag number=4 C, G, O, V, or X = relevant part of the Hipparcos Double and Multiple Systems Annex, from Field H59 (Cat. <I/239>), C: solutions for the components G: acceleration or higher order terms O: orbital solutions V: variability-induced movers (apparent motion arises from variability) X: stochastic solution (probably astrometric binaries with short period) supplemented by S = suspected binary in Hipparcos Catalogue, from Field H61, Cat. <I/239>, (see paper for details) --- Dist Distance from the cluster centre defined by the 134 stars within r<10 pc (see Table 3) pc Stat Kinematic statistic number=5 A value of 14.16 corresponding to 3{sigma}, see paper for details. --- Memb Final membership assigned in this paper `?' indicates possible new members unclassifiable due to unknown radial velocities --- Patricia Bauer CDS 1997Jul24Anthony Brown <brown@strw.LeidenUniv.nl> J_A+A_331_81.xml