1. Introduction 2. Hyades Supercluster

Home , 27 Cancri, NGC 1901

THE AGE RANGE OF HYADES STARS OLIN J. EGGEN Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories,1 Casilla 603, La Serena, Chile; oeggen=noao.edu Received 1997 December 29; revised 1998 March 12 ABSTRACT On the basis of canonical models, the age of Hyades supercluster stars, whether in the Hyades and Praesepe clusters or the noncluster Ðeld, ranges from (5È6) ] 108 to 109 yr. The di†erence between the parallax derived from the supercluster motion and that obtained from Hipparcos observations has a dispersion only twice that of the mean dispersion of the individual Hipparcos values. The supercluster appears not to contain red giants on the Ðrst ascent of the red giant branch, but only asymptotic giant branch (““ clump ÏÏ) stars. The masses obtained for individual components of binary stars in the supercluster show a dispersion of less than 10% when compared with model predictions. Key words: open clusters and associations: individual (Hyades) È stars: evolution

1. INTRODUCTION where (t, q) are the components of the proper motion in the direction of the convergent point (a, d) and perpendicular to The Hyades cluster, because of its depth-to-distance that direction, respectively; and ratio, has become the basis for the universal metric. The lowest mass cluster members form a cluster halo, and the n \ 4.74t/(V sin j) , (3) cluster itself, together with its near-twin the Praesepe clus- clus tot whereV is total space motion of the supercluster relative ter, is part of the Hyades supercluster. This supercluster, to the Suntot and j is the angular distance between the star together with another, the NGC 1901 supercluster, forms and (a, d). The photometric luminosities have been derived the main constituent of star stream I, for which the apex of from the photometric calibrations listed in Eggen (1996). the proper motions is (a,d) \ (6h.4, 6¡.5) (B1950.0). Previous investigations of the cluster and superclusters have shown a 2. HYADES SUPERCLUSTER wider range of agesÈ8 ] 108 to 2 ] 109 yrÈthan can be 2.1. Upper Main Sequence easily explained as one, prolonged star birth event. The present discussion will be divided into two parts, The parameters for upperÈmain-sequence members of the with the upper main sequence of the supercluster discussed Hyades supercluster are listed inTable 1, where the stars in° 2.1 and red giants in° 2.2. The b photometry is mainly are identiÐed by HR, HD, and Hipparcos (ESA 1997) from the compilation byHauck & Mermilliod (1980), and numbers. Only stars not known to have photometrically the RI photometry is on the system deÐned in Eggen unresolved companions from 0.2 to 3.2 mag fainter are con- (1979). The proper motions are on the FK5 system and are sidered. The total space motion is from the references in the notes toTable 1. The observed V \ 43.5 ] 0.045X (4) radial velocities are mainly fromAbt & Biggs (1972) and tot (Eggen 1992b), where X is the distance in parsecs of the star Barbier-Brossat,Petit, & Figon (1994). For the upperÈ from the Sun in the direction opposite that of the Galactic main-sequence stars, the values oflog T are based on b. center. The computed values of the radial velocity are given A previous discussion(Eggen 1995) foundeff that by log T \ 3.881 ] 0.53(b [ 2.800) , (1) eff o \ V cos j . (5) derived from spectrophotometry(Smalley & Dworetsky comp tot The mean di†erence,, omitting the variable- 1993) for a range of Am, ultraÈshort-period Cepheid o [ o velocity stars, is 0.3 obs2.4 (1 compp)kms ,or 0.35 2.50 (USPC; d Scuti), and normal AF stars, as well as fundamen- [ ^ ~1 [ ^ km s if we include those with variable velocity. The dis- tal values ofT (Andersen 1991) derived from eclipsing ~1 persion in the mean peculiar velocity is higher, as expected, binaries. The meaneff dispersion of the di†erence between the from the supercluster members, 0.27 2.50 km s , than spectrophotometric values and those from equation (1) is [ ^ ~1 it is for the members of the Hyades cluster, 0.26 0.66 100 K. The temperatures for the red giants are from ] ^ ^ km s . BessellÏs (1979)calibration of the [(R I) , log T ] rela- ~1 [ The mean modulus for the Hyades cluster members in tion. C eff Table 1 is 3.29 mag from the cluster motion and 3.37 mag The convergent point of the proper motion of stars in from the Hipparcos parallaxes. The motion parallaxes from stream I is at (a,d) (6.4, 6¡.5) (Eggen 1996). The stars \ h the Hipparcos convergent point(Perryman et al. 1998) yield discussed here are mainly of magnitude V \ 7 and peculiar a mean modulus of 3.33 mag, andSchwan (1991) found 3.40 velocityP.V. ¹ 0.1V , with M (clus) M (phot) \ 0.25 V [ V mag. The comparison between the cluster parallaxes in mag. Here tot Table 1 and the Hipparcos results is almost identical to that P.V. \ 4.74qD(pc) , (2) discussed by Perryman et al. The overall comparison for the supercluster stars in Table 1 yields n n 0.13 1.84 mas. Four stars are omitted from ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ [ \ ^ thisclus comparison,Hip listed inTable 2. The convergent point of 1 The National Optical Astronomy Observatories are operated by the Association of Universities for Research in Astronomy, Inc., under co- the proper motions of a critically selected 20 cluster operative agreement with the National Science Foundation. members(Perryman et al. 1998) is (a,d) \ (6h.52, 6¡.66), com- 284 TABLE 1 MEMBERS OF THE HYADES SUPERCLUSTER

o (km s~1) n (mas) k XV P.V. SPECTRAL tot HR (HD) REFERENCEa (pc) (km s~1) Obs. Comp. (km s~1) M log T Cluster Hip. p TYPE NOTES HIP V eff 125...... 1 [15 42.8 [2V [2.9 ]1.2 ]0.79 3.936 16.0 18.97 0.64 A1 E 2472 238...... 2 30 45.1 ]2.3 ]1.4 ]0.8 ]2.15 3.865 14.9 15.00 0.72 F3 IV 1 3865 343...... 2 23 44.55 ]9.4 ]9.1 ]0.5 ]1.28 3.905 24.8 23.73 0.68 A7 V 2 5542 (8391) ...... 2 [5 43.25 ]4.2 ]4.2 ]1.4 ]2.83 3.843 14.4 12.70 0.80 F1 V 2 6418 403...... 1 18 44.3 ]7V ]10.0 ]0.2 ]0.28 3.896 33.1 32.81 0.41 A5 IV 3 6686 520...... 3 [8 43.1 ]8.0 ]4.6 ]2.9 ]0.97 3.934 15.3 17.54 0.62 A1 V 8241 607...... 3 54 45.95 ]15.0 ]18.5 ]4.0 ]0.30 3.902 9.1 11.31 0.85 A5 III 9589 733...... 2 31 44.9 ]24V ]18.4 ]1.3 ]2.27 3.859 10.0 9.39 0.92 F0 III 4 11644 878...... 1 25 44.55 ]28.5 ]27.0 ]0.2 ]3.28 3.820 31.2 31.40 0.84 F5 IV 13834 1036 ...... 3 144 50.0 ]34.5 ]31.3 ]0.9 ]1.06 3.889 5.8 7.78 1.66 A3 Vp 5, 6 16077 1125 ...... 2 30 45.75 ]30.0 ]32.2 [1.0 ]2.06 3.830 12.7 10.98 0.90 F2 V 17214 1201 ...... 1 35 45.1 ]35.0 ]35.1 [0.3 ]2.92 3.836 24.3 24.14 0.90 F4 V 7 18170 1233 ...... 2 37 45.15 ]36: ]34.6 ]0.5 ]3.30 3.812 23.6 25.42 1.05 F5 V 7 18658 1279 ...... 2 38 45.2 ]36.4 ]36.7 [0.1 ]2.84 3.824 23.2 21.27 1.03 F3 V 7 19261 (26345) ...... 2 40 45.3 ]35.0 ]36.8 ]0.1 ]3.44 3.815 22.7 23.22 0.92 F6 V 7 19504 1292 ...... 3 30 44.85 ]36.8 ]37.4 [0.6 ]3.07 3.829 28.5 25.89 0.95 F4 V 7 19554 1319 ...... 2 43 45.45 ]36.4 ]37.5 ]2.2 ]3.06 3.827 22.4 22.51 0.82 F5 V 7 19877 (26737) ...... 2 51 45.8 ]3.75 ]38.4 ]0.8 ]3.42 3.814 18.0 18.12 0.82 F5 V 7 19789 1351 ...... 2 40 45.3 ]42.0 ]38.4 ]0.1 ]2.48 3.864 23.9 22.31 0.92 F0 V 7, 8 20219 1354 ...... 4 41 45.35 ]42.0 ]38.0 [0.8 ]2.97 3.824 22.7 21.12 0.77 F2 V 7 20255 1356 ...... 2 41 45.35 ]36.2 ]38.4 [0.6 ]2.07 3.887 22.4 21.20 0.99 F0 IV 7, 9 20261 (27534) ...... 2 43 45.45 ]3.1 ]37.8 ]0.4 ]3.55 3.815 21.6 19.83 0.89 F5 V 7 20350 1368 ...... 2 40 45.3 ]41.2 ]38.5 [0.6 ]2.54 3.858 22.4 21.87 0.66 Am 7, 10 20400 1380 ...... 2 41 45.35 ]37.5 ]38.1 [0.3 ]1.62 3.910 22.7 22.36 0.88 A8 V 7 20542 (27848) ...... 2 43 45.45 ]37.1 ]37.8 ]0.4 ]3.54 3.804 20.3 18.74 1.17 F6 V 7 20567 1385 ...... 2 41 45.35 ]36.6 ]38.6 ]1.2 ]2.86 3.831 23.0 20.40 0.74 F3 V 7 20614 1387 ...... 2 43 45.45 ]40.1 ]38.9 ]0.5 ]0.96 3.917 21.8 21.27 0.86 A6 V 7 20635 1388 ...... 2 40 45.3 ]33.0 ]38.0 ]0.4 ]2.18 3.871 23.4 22.65 0.84 A5 Vm 7, 11 20641 1389 ...... 2 40 45.3 ]40.2 ]38.9 ]0.6 ]1.14 3.929 23.1 22.05 0.77 A2 IV 7 20648 1391 ...... 2 42 45.4 ]36.4 ]38.9 [0.6 ]4.01 3.795 22.0 21.47 0.97 F7 V 6, 7, 12 20661 1403 ...... 2 46 45.55 ]37.5 ]38.3 ]0.2 ]2.36 3.868 20.7 20.85 0.86 Am 7 20842 1408 ...... 2 40 45.3 ]44.2 ]39.0 ]0.8 ]2.79 3.853 23.0 18.42 1.93 F2 V 7 20873 1412 ...... 2 40 45.3 ]39.5 ]38.9 ]0.4 ]0.61 3.897 22.9 21.89 0.83 A7 IV 7, 13 20894 1414 ...... 4 41 45.35 ]33.4 ]39.5 ]0.4 ]1.85 3.897 22.5 20.33 1.34 A7 V 7 20901 (28394) ...... 2 41 45.35 ]39.8 ]39.0 ]0.1 ]3.79 3.795 22.6 23.24 1.04 F8 V 7, 14 20935 1427 ...... 2 42 45.4 ]37.5 ]39.2 ]0.7 ]1.58 3.910 22.4 22.54 0.77 A7 V 6, 7 21029 1428 ...... 2 42 45.4 ]39.3 ]39.2 ]0.5 ]2.24 3.885 21.9 22.55 1.09 Am 7 21039 1430 ...... 2 40 45.3 ]38.8 ]39.4 ]0.2 ]2.30 3.883 23.2 21.84 0.89 F0 V 7 21036 (28608) ...... 2 40 45.3 ]41.3 ]39.7 [0.1 ]3.89 3.805 22.4 22.96 0.99 F7 V 7 21066 1432 ...... 2 39 45.25 ]36.0 ]39.4 [0.4 ]2.91 3.841 23.9 22.25 1.14 F2 V 7 21137 1436 ...... 2 35 45.0 ]39.8 ]39.6 [0.3 ]3.47 3.812 25.3 25.13 0.90 F5 V 7 21152 1459 ...... 2 39 45.25 ]43.3 ]38.6 ]0.5 ]3.05 3.833 24.5 22.60 0.76 F5 IV 7 21459 1472 ...... 2 43 45.45 ]38.4 ]40.1 [0.3 ]2.50 3.857 21.8 21.96 1.04 F2 V 7 21588 1473 ...... 3 39 45.25 ]45.0 ]40.2 ]1.0 ]1.18 3.918 23.7 21.75 0.79 A6 V 7 21589 1479 ...... 3 50 45.75 ]36.9 ]40.4 ]1.6 ]1.12 3.909 18.7 20.51 0.82 A6 IV 7 21683 1480 ...... 2 42 45.4 ]36.3 ]40.5 [0.6 ]2.09 3.885 21.3 19.44 0.86 A9 III 7 21670 1507 ...... 2 38 45.2 ]39.4 ]41.0 [0.4 ]2.38 3.876 24.2 20.73 0.88 A3 IV 7 22055 1519 ...... 4 56 46.0 ]43.0 ]41.4 ]1.7 ]1.48 3.903 16.4 12.24 0.86 Am 7, 15 22157 1547 ...... 1 47 45.6 ]38.5 ]40.9 ]0.4 ]1.70 3.888 20.4 17.27 0.82 A9 V 6, 7 22565 1554 ...... 2 89 47.5 ]38.0 ]40.7 ]1.0 ]1.26 3.829 11.0 9.27 0.88 F2 IV 22697 1566 ...... 2 59 46.15 ]35.0 ]41.3 ]0.7 ]2.57 3.849 16.5 14.67 0.95 F1 V 7 22850 1620 ...... 1 52 45.85 ]42.2 ]41.5 ]0.5 ]1.05 3.906 18.8 20.01 0.91 A7 V 7 23497 1670 ...... 1 55 46.0 ]45.0 ]40.5 [0.6 ]2.25 3.879 17.7 18.25 1.30 Am 7 24019 1672 ...... 1 47 45.6 ]39.2 ]43.0 ]0.4 ]2.10 3.890 20.0 18.54 0.83 Am 7, 16 23983 1700 ...... 2 29 42.2 ]8.0 ]7.5 ]3.5 ]0.60 3.933 7.3 7.20 0.48 A1 V 23737 1905 ...... 2 46 45.55 ]41.0 ]43.8 ]0.3 ]2.24 3.885 21.2 18.56 0.86 F0 V 7 26382 2566 ...... 2 76 46.9 ]40.9 ]42.0 ]0.2 ]0.80 3.910 7.8 7.12 0.72 Am 33079 2666 ...... 1 28 44.75 ]28: ]29.0 [3.5 ]1.01 3.908 10.0 10.34 0.56 Am 6 34081 2700 ...... 3 97 47.8 ]40V ]43.6 [0.6 ]0.74 3.901 9.8 8.36 0.80 A4 IV 34722 3495 ...... 3 [14 42.9 ]9.0 ]10.1 [2.3 ]1.90 3.887 13.5 16.49 0.46 A4 V 42895 3686 ...... 2 105 48.25 ]32.0 ]31.6 [3.0 ]0.87 3.896 6.7 10.46 2.67 A5 IV 45661 4033 ...... 1 27 44.2 ]17.0 ]20.8 [3.1 ]0.10 3.920 20.9 24.27 0.75 A2 III 50372 4082 ...... 1 45 45.55 ]23.0 ]22.7 ]3.0 [0.20 3.900 20.0 9.28 0.72 A2 Vp 50885 (97840) ...... 2 [10 43.05 ]5.2 ]8.4 [4.5 ]3.24 3.824 17.2 16.10 0.81 F4 IV/V 54938 4453 ...... 2 [29 42.2 ]9.0 ]4.4 [2.8 ]1.11 3.920 9.7 8.86 1.32 A2 IV/V 6 56391 4543 ...... 4 6 43.75 ]7.0 ]7.7 [2.5 ]2.35 3.867 15.2 16.08 0.74 Am 57779 4547 ...... 3 [5 43.3 ]9.1 ]6.2 ]2.3 ]3.55 3.818 26.8 22.25 0.80 F3 IV 57819 4599 ...... 2 [27 42.3 [2.4 [2.3 [1.4 ]1.29 3.838 16.9 14.19 0.54 Ap 6, 17 58758 4694 ...... 2 6 43.75 ]4.0 ]3.2 [1.6 ]2.17 3.851 15.5 16.50 0.72 F0 V 60168 4715 ...... 4 26 44.7 0V ]3.9 [4.0 ]0.75 3.832 8.4 9.75 0.69 F3 IV 18 60467 286 EGGEN Vol. 116

TABLE 1ÈContinued

o (km s~1) n (mas) k XV P.V. SPECTRAL HR (HD) REFERENCEa (pc) (kmtot s~1) Obs. Comp. (km s~1) M log T Cluster Hip. p TYPE NOTES HIP V eff 4866 ...... 2 30 44.85 [1.5 ]1.1 [1.2 ]0.51 3.914 7.9 7.04 0.66 A7 V 62516 (112734) ...... 2 [1 43.45 [6V [3.1 ]4.2 ]2.48 3.885 12.0 13.38 0.85 A5 63320 5084 ...... 1 [48 41.35 [7V [3.6 ]4.5 ]0.77 3.908 10.7 12.71 0.41 Am 66753 5229 ...... 4 [12 42.95 [14.5 [11.5 ]3.3 ]1.74 3.898 14.6 15.46 0.79 A8 IV 67782 (121141) ...... 2 [53 41.1 [16V [13.6 [0.7 ]2.78 3.836 17.3 13.44 0.94 F2 V 5290 ...... 2 [33 42.0 [20V [18.0 ]0.8 ]1.66 3.840 17.5 18.22 0.53 F0 IV 68740 5491 ...... 1 [37 41.85 [9V [5.7 [2.9 ]2.23 3.865 13.6 15.54 0.50 Am 19 75736 6767 ...... 2 [22 42.5 [30V [28.1 ]1.9 ]2.29 3.859 14.8 17.44 0.56 A9 V 88565 6871 ...... 2 [58 40.9 [21.1 [22.6 ]0.5 ]1.95 3.880 14.2 14.02 1.45 A7 V 90384 7124 ...... 1 32 44.95 [8.4 [6.2 ]3.6 ]0.65 3.900 8.0 10.73 0.48 A2 Vp 6, 15 92112 7984 ...... 2 [4 43.3 [24.0 [22.0 [0.2 ]1.90 3.909 22.1 23.67 0.56 A6 V 102843 8278 ...... 1 [26 42.6 [31.0 [28.5 [0.3 ]2.60 3.870 28.7 23.48 1.10 Am 106985 8518 ...... 1 [19 42.65 [20V [22.2 [2.2 ]0.10 3.908 18.2 20.67 1.71 A0 V 110395 8547 ...... 1 [29 42.2 [12.4 [15.0 [0.1 ]2.08 3.888 19.5 22.96 0.60 A4 V 110935 8586 ...... 2 [4 43.3 [18.9 [17.6 [4.5 ]3.04 3.836 20.2 18.90 0.83 F2 V 111278 8786 ...... 2 [43 41.55 [7.0 [7.0 [4.5 ]1.48 3.920 14.6 13.44 0.49 A6 Vm 114257 8977 ...... 3 11 44.0 [18.8 [15.5 [4.5 ]3.35 3.619 25.4 22.63 0.81 G0 V 116824

NOTES.È(1) V526 Cas, USPC (P \ 0.05 days); (2) suspected variable (HR 343 \ CSV 100091); (3) d Cas, unconÐrmed eclipsing binary; (4) TY For, USPC (P \ 0.05 days); (5) CHARA 10; (6) equal components; (7) Hyades cluster star; (8) V696 Tau, USPC (P \ 0.05 days); (9) V696 Tau, USPC (P \ 0.04 days); (10) V773 Tau, USPC (P \ 0.06 days); (11) i2 Tau (period?); (12) P \ 13 yr; (13) h2 Tau (seeEggen 1995), USPC (P \ 0.07 days); (14) spectroscopic binary, P \ 239 days; (15) spectroscopic binary; (16) spectroscopic binary, P \ 156 days; (17) spectroscopic binary, P \ 24 days; (18) AI CVn, USPC (P \ 0.14 days); (19) BP Oct, USPC (P \ 0.08 days). a Proper-motion references: (1) FK5,Fricke et al. 1988; (2) FK5 supplement, Schwan et al. 1993; (3) FK5 Extension, Fricke, Schwan, & Corbin 1991; (4) Hipparcos Catalogue, ESA 1997. pared with (a,d) \ (6h.4,6¡.5) for the stars in stream I (Eggen has been compensated for by subtracting 0.10 mag from the 1996). model values ofMV (seeEggen 1986, Fig. 19). Based on the The (logT , MV) array for the stars in Table 1 is shown arguments byCastellani et al. (1992) against the presence of inFigure 1. eff The Hyades cluster stars are represented by convective overshoot at the core, the canonical models have Ðlled circles, and the noncluster, supercluster members by been adopted here. Use of models with convective over- open circles. The Praesepe cluster stars are mostly fainter in apparent magnitude than the objects inTable 1, but the cluster is almost an identical twin of the Hyades cluster. The Praesepe stars that are not known to have photometrically unresolved companions between 0.2 and 3.0 mag fainter are listed inTable 3. These stars are represented in Figure 1 by crosses. The adopted modulus of Praesepe is 6.35 mag, derived from the 3.0 mag di†erence between the Hyades and Praesepe main sequences and the mean modulus of 3.35 mag for the Hyades. The Praesepe cluster, as a member of the Hyades group, is discussed in Eggen(1992a, 1996). The adopted parallax of 5.4 mas agrees well with the main Hip- parcos value inTable 4 of 5.51 ^ 0.96 mas. The supercluster members withT [ 7500 K are shown inFigure 1a, and the lower temperatureeff objects are in Figure 1b.The isochrones in the Ðgure are from Castellani, Chieffi, & Straniero(1992). The models have Y \ 0.27 and Z \ 0.02, whereas the expected value for the supercluster is probably nearer Z \ 0.025. However, this small di†erence

TABLE 2 STARS OMITTED FROM HYADES PARALLAX COMPARISON

n (mas)

HR Cluster Hip. p

1408a ...... 23.0 18.42 1.98 1519a ...... 16.4 12.24 0.86 4547b ...... 26.8 22.25 0.80 8748b ...... 28.7 23.48 1.10

a Hyades cluster(Perryman et al. 1998). b Supercluster. FIG. 1.È Hyades supercluster members in the (log T , M )-plane eff V No. 1, 1998 AGE RANGE OF HYADES STARS 287

TABLE 3 MEMBERS OF THE PRAESEPE CLUSTER

Spectral Spectral HD/BD M log T Type Notes HD/BD M log T Type Notes V eff V eff 72779 ...... ]0.21 3.779 G0 III 73712 ...... ]0.32 3.858 A9 V 72942 ...... ]1.12 3.908 K9 V 73729 ...... ]2.60 3.850 F0 V 6, 8 73161 ...... ]2.34 3.845 F0 V 73730 ...... ]1.65 3.901 Am 73174 ...... ]1.50 3.904 Am 73731 ...... ]0.69 3.901 A6 III 6 73175 ...... ]1.89 3.876 F0 IV 1 73746 ...... ]2.29 3.853 F0 V 9 73210 ...... ]0.38 3.886 A5 V 73763 ...... ]1.45 3.879 A9 V 10 73345 ...... ]1.80 3.889 F0 V 2 73785 ...... ]0.48 3.889 A9 III 73397 ...... ]2.63 3.844 F2 V 73798 ...... ]2.12 3.862 F0 V 11 73430 ...... ]1.95 3.888 A9 V 73818 ...... ]2.30 3.854 Am 73449 ...... ]0.89 3.859 A9 V 73819 ...... ]0.41 3.890 A6 V 73450 ...... ]2.13 3.865 A9 V 73854 ...... ]2.66 3.832 F5 V 73575 ...... ]0.31 3.869 F0 III 3 73872 ...... ]1.97 3.887 A5 V 73576 ...... ]1.30 3.887 A7 V 4 73993 ...... ]2.18 3.848 F2 V 73597 ...... ]2.98 3.825 F2 V ]20¡2193 ...... ]3.31 3.806 F4 V 73616 ...... ]2.35 3.839 F2 V 74028 ...... ]1.60 3.887 A7 V 12 73618 ...... ]1.70 3.905 Am ]20¡2196 ...... ]3.78 3.800 F6 V 73619 ...... ]1.94 3.894 Am 5, 6 ]19¡2050 ...... ]3.09 3.815 F5 V 73666 ...... ]0.25 3.917 Ap 7 ]19¡2089 ...... ]3.63 3.799 F5 73709 ...... ]0.34 3.904 Am ]20¡2198 ...... ]3.80 3.799 F6 73711 ...... ]1.18 3.192 Am

NOTES.È (1) BR Cnc, USPC (P \ 0.04 days); (2) CY Cnc, USPC (P \ 0.1: days); (3) BT Cnc, USPC (P \ 0.10 days); (4) BU Cnc, USPC (P \ 0.074 days); (5) spectroscopic binary, P \ 12 days; (6) equal components; (7) 40 Cnc (binary?); (8) BQ Cnc, USPC (P \ 0.07 days); (9) BV Cnc, USPC (P \ 0.21: days); (10) BN Cnc, USPC (P \ 0.04 days); (11) BW Cnc, USPC (P \ 0.07 days); (12) BX Cnc, USPC (P \ 0.05 days). shoot at the core (e.g.,Maeder & Meynet 1991) would Ðgure. The symbols are as inFigure 1. Two stars not in increase the ages by a factor near 1.5. Table1 or 3 have been added to Figure 2b: the large- The minimum age of the supercluster stars, including amplitude USPC stars VZ Cnc and d Sct (Table 5). both the Hyades and Praesepe cluster members, appears to be (5È6) ] 108 yr. However, both Figures1a and1b show 1. VZ Cnc is about 10¡, or 30 pc, from the center of the evidence that older stars exist in all three components (two Praesepe cluster. Eleven cluster members in the Hipparcos clusters and noncluster Ðeld) of the supercluster. The Am Catalogue, as well as VZ Cnc, yield the results shown in stars and USPC (d Scuti) variables in the supercluster are Table 4. The variable and the cluster appear to be at the represented in Figures2a and2b, respectively. The compli- same distance with nearly the same proper motion. The cated double star HR 1412 has been omitted from the mean cluster radial velocity is ]34 km s~1, and Abt (1955)

TABLE 4 ASTROMETRY OF PRAESEPE MEMBERS AND VZ CANCRI

a (J2000.0) d (J2000.0) k k p(k , k ) np(n) a d a d HD HIP (hr) (deg) (mas yr~1) (mas yr~1) (mas yr~1) (mas) (mas) 72779 ...... 42133 8.58 ]19.59 [35.66 [12.82 1.06, 0.72 5.57 0.91 72942 ...... 42201 8.60 ]20.34 [35.96 [12.96 1.18, 0.81 7.11 1.13 73175 ...... 42319 8.63 ]19.50 [36.65 [11.37 1.28, 0.99 5.80 1.19 73210 ...... 42327 8.63 ]19.27 [35.55 [12.28 0.99, 0.78 5.10 1.02 73665 ...... 42516 8.67 ]20.04 [35.02 [11.77 1.04, 0.71 5.55 0.89 73666 ...... 42523 8.67 ]19.97 [34.86 [14.92 0.97, 0.65 5.72 0.84 73710 ...... 42549 8.67 ]19.67 [35.22 [13.15 0.97, 0.68 4.31 0.93 73731 ...... 42556 8.67 ]19.54 [33.74 [13.57 0.91, 0.67 5.95 0.91 73785 ...... 42578 8.68 ]19.72 [34.26 [11.96 0.98, 0.65 6.49 0.93 73819 ...... 42600 8.68 ]19.58 [33.61 [10.54 0.95, 0.62 5.46 0.93 73994 ...... 42673 8.70 ]19.87 [34.85 [14.25 0.97, 0.67 3.55 0.90 Mean ...... 8.65 ]19.74 [34.9 [12.7 5.51 p ...... ^0.90 ^1.3 ^0.96 VZCnc...... 42594 8.68 ]9.82 [29.88 [15.55 1.08, 0.87 5.43 0.99

TABLE 5 COMPARISON STARS IN FIGURE 2b

MV P STAR n n n n Mean log T (days) clus phot PvL Hip eff VZCnc...... ]1.30 ]1.51 ]1.45 ]1.25 ]1.39 3.844 0.178 d Sct...... ]1.38 ]1.37 ]1.06 ]1.27 3.850 0.194 288 EGGEN Vol. 116

TABLE 6 SUPERCLUSTER MEMBERS WITH T D 7450 K eff Spectral Age HR (HD) M log T Type d (yr) Notes V eff (73210) ...... ]0.38 3.886 A5 V 1.395 6 ] 105 1 (73819) ...... ]0.41 3.890 A6 V 1.422 1 (73785) ...... ]0.48 3.889 A9 III 1.391 1 3686 ...... ]0.87 3.896 A5 IV . . . 8 ] 108 1036 ...... ]1.06 3.889 A3 Vp 1.361 2, 3 (73756) ...... ]1.30 3.887 A7 V 1.313 1, 4 (74028) ...... ]1.60 3.887 A7 V 1.248 1, 4 1547 ...... ]1.70 3.888 A9 V 1.276 3, 5 5229 ...... ]1.74 3.898 A8 IV . . . 1414 ...... ]1.85 3.897 A7 V 1.266 5 3495 ...... ]1.90 3.887 A4 V 1.238 (73619) ...... ]1.94 3.887 Am . . . 1, 3 6871 ...... ]1.95 3.880 A7 V 1.294 1356 ...... ]2.07 3.887 F0 IV . . . 4, 5 1672 ...... ]2.10 3.890 Am 1.202 2, 5 1905 ...... ]2.24 3.885 F0 V 1.214 5 1430 ...... ]2.30 3.883 F0 V 1.172 5 (112734) ...... ]2.48 3.885 A5 . . . 6 ] 108 NOTES.È(1) Praesepe cluster; (2) spectroscopic binary; (3) equal components; (4) USPC; (5) Hyades cluster.

(B1 [ B2), where the median e†ective wavelengths are 3464 ÓÓfor U, 4015 for B1 and 4476 Ó for B2. It is therefore FIG. 2.ÈRecognized (a) Am and (b) USPC members of the supercluster possible to conclude that these supercluster stars have a in the (log T , MV)-plane. eff range of ages at least from 5È6to8]108 yr. Much of the dispersion in Figure 3 can be accounted for by the tem- found a mean of 30 km s for the variable from 92 ] ~1 perature range adopted inTable 6 and the strong depen- plates.McNamara & Rogers (1962) and Balona & Stobie dence of F on temperature, in the expression M A (1983), from 14 and 103 plates, respectively, found ranges V \ F *d. The same procedure has been applied to the stars from about 0 to 55 km s for the variable. The value of ] ] ~1 inTable 7 withT between 6950 and 7330 K that populate M fromn is derived from the Praesepe modulus of 6.35 V the main-sequenceeff turno† region of models with age near mag andnclus from the parallax in Table 4. The period- 10 yr. Values of the cluster luminosity are correlated with luminosity relationHip (Eggen 1994b) givesM 2.80 log P 9 V \[ the photometric luminosity parameter d inFigure 4, where, [ 0.60 \]1.45 mag. The periods of the fundamental modes(Templeton et al. 1997; Fitch 1976) are listed in Table 5. 2. d Sct, at B1950.0 coordinates(18h.65, [9¡.1), is very near the antapex of the stream I proper motions, so the predicted stream motion in the tangential direction is nearly zero and the star is an FK5 standard with the very small motion of(k , k ) \ (9, 2) mas yr~1. The predicted radial a d velocity is [45.6 km s~1, compared with an observed value of [44 km s~1 from 23 plates, and this agreement, together with that of the luminosities from photometric parallaxes and the period-luminosity relation, is the basis for accepting the star as a member of the Hyades supercluster. This object is labeled in Figure 2b. The stars inTable 6 represent a cross section of the (MV, log T )-planeof Figure 1aT at\ 7450 ^ 85 K, where eff eff the dependence ofMV on d changes very little with temperature change. One main-sequence object and three highly evolved members of the Praesepe cluster give the same age, 6 ] 108 yr, as the other hotter stars, but members of all three supercluster componentsÈPraesepe, Hyades, and nonclusterÈdeÐne a main-sequence turno† with an age of 8 ] 108 yr. The location in Figure 1 of these stars is not inÑuenced by undetected binaries, as shown by Figure 3, where the cluster luminosities are correlated with the luminosity parameter, d, of the Geneva photometric system FIG. 3.ÈCross section inMV of the temperature-luminosity array near (Rufener 1988). The d-parameter is Geneva equivalent T \ 7450 K. The d-index is a luminosity parameter in the Geneva pho- of[c ] in the Stro mgren system; d \ (U[B) [ 1.430 ] tometry.eff 1 No. 1, 1998 AGE RANGE OF HYADES STARS 289

TABLE 7 SUPERCLUSTER MEMBERS WITH TEMPERATURE NEAR 7100 K AND AGE NEAR 109 yr

Spectral Age HR (HD) M log T Type d (yr) Notes V eff VZCnc...... ]1.39 3.844 . . . 1.206 109 USPC (73798) ...... ]2.12 3.862 F0 1.191 Praesepe, USPC 238...... ]2.15 3.865 F2 IV 1.135 4694 ...... ]2.17 3.851 F0 V 1.131 (73993) ...... ]2.27 3.859 F0 IV 1.150 (73746) ...... ]2.29 3.853 F0 V 1.130 Praesepe, USPC 1472 ...... ]2.50 3.857 F2 V 1.109 Hyades 1368 ...... ]2.54 3.859 Am 1.104 Hyades, USPC 1566 ...... ]2.57 3.849 F1 V 1.126 Hyades (73397) ...... ]2.63 3.844 F2 V 1.066 Praesepe 1432 ...... ]2.91 3.841 F2 V 1.043 Hyades again, most of the dispersion can be accounted for by the all of the components of the Hyades supercluster (cluster substantial temperature range included. Figure 3 quantiÐes and noncluster members) show a larger range in age than the dispersion around the isochrones seen in Figure 1. can easily be understood as representing a single, prolonged It is difficult to avoid the conclusion that, like the epoch of star formation. Pleiades supercluster (see, e.g., Herbig 1964; Eggen 1977), 2.2. Red Giants The red giants in the supercluster are listed in Table 8, where the data are of the same type as provided in Tables 1 and2. The temperatures are derived from BessellÏs (1979) calibration of R[I (Eggen 1994a). The Hyades cluster, Praesepe cluster, and noncluster supercluster members of Table 8 are represented inFigure 5, which also contains an isochrone for 6 ] 108 yr (Z \ 0.02, Y \ 0.27). These evolved stars are apparently part of the youngest popu- lation in the supercluster, (5È6) ] 108 yr. Figure 5 seems to conÐrm earlier indications that there are no red stars on the Ðrst-ascent giant branch but that, instead, they populate the asymptotic giant branch, or ““ clump.ÏÏ The mean di†erence ofn [ n \ 0.71 ^ 1.70 mas is very similar to the result obtainedclus fromHip the stars in Table 1. 2.3. Masses Twenty visual binaries, and the double-lined eclipsing variable HD 27130 (V818 Tau), are members of the supercluster and are described inTable 9. The two binaries of lowest luminosity are not in the Hipparcos Catalogue, and the mean, ground-based parallaxes are listed in the table. It is notable that the dispersion in the Hipparcos parallax for most of these binaries is nearly double that of the single FIG. 4.ÈSame asFig. 3, but forT near 7150 K stars inTable 1 but that the mean di†erence is n eff clus TABLE 8 EVOLVED RED STARS IN THE HYADES SUPERCLUSTER

o (km s~1) n (mas) XV P.V. SPECTRAL HR (HD) (pc) (kmtot s~1) Obs. Comp. (km s~1) M Cluster Hip. p log T TYPE HIP NOTES V eff 1346a ...... 37 45.2 ]38.6 ]38.0 ]0.5 ]0.45 22.8 21.7 1.17 3.690 K0 III 20205 1 1373a ...... 36 45.15 ]37.6 ]38.2 ]1.3 ]078 25.3 21.29 0.93 3.695 K0 III 20455 1, 2, 3 1409a ...... 42 45.35 ]38.4 ]39.0 0.0 ]0.38 23.2 21.04 0.82 3.695 G9 III 20889 1 1549b ...... 53 45.9 ]37.3 ]38.5 ]3.0 ]0.48 12.9 13.4 0.68 3.705 K0 III 22479 (73598) ...... ]0.25 5.4 4.50 1.72 3.695 K0 III 42497 4 (73665) ...... ]0.05 5.4 5.55 0.89 3.695 K0 III 42516 4 (73710) ...... ]0.08 5.4 4.31 0.93 3.680 K0 III 42549 4 (73974) ...... ]0.55 5.4 3.55 0.90 3.695 K0 III 42673 4 4171b ...... 9 43.9 ]16.2 ]17.6 [0.2 ]0.27 12.0 14.52 0.89 3.700 G6 III 52085 2 4253b ...... 17 44.25 ]15.8 ]16.6 [1.7 ]0.40 9.8 10.45 0.78 3.690 G8 III 53273 4409b ...... [19 42.65 ]4.3 ]6.1 ]3.6 ]0.75 12.2 11.64 0.78 3.700 K0 III 55786

NOTES.È(1) Hyades cluster; (2) spectroscopic binary; (3) P \ 530 days; (4) Praesepe cluster. a FK5 proper motion(Fricke et al. 1988). b Hipparcos proper motion (ESA 1997). 290 EGGEN Vol. 116

FIG. 5.ÈThe(log T , MV) relation for the evolved red stars in the supercluster. eff

[ n \ 0.79 ^ 1.97 mas, omitting HD 38. The individual componentsHip for 17 systems are listed inTable 10, where the individual magnitudes and colors are based on the results for the combined light and the observed di†erence in visual magnitude(Eggen 1984). The references for the orbital parameters are listed in the last column of the table. The FIG. 6.ÈThe (logT , MV) relation for the individual components of visual binaries in the supercluster.eff (logT , MV) relation for the stars in Table 10 is shown in Figureeff 6, where Hyades cluster members are represented by Ðlled circles and noncluster supercluster members by open circles. The adopted temperatures are from the (B[V , log and Wolf 424AB), together with the C component of HD T )relation of Bessell (1979). The isochrones for 6 ] 108 186602, are listed inTable 11, where the values of M (clus) eff I and 109 yr (Z \ 0.025) are those for Z \ 0.020 with MV are based on the cluster parallax(Table 1) and the orbital decreased by 0.1 mag(Castellani et al. 1992). parameters, with references, are in the rightmost columns of The I magnitudes and R[I colors of components of the the table. Previously(Eggen 1993), it was found that the three systems of lowest luminosity (HD 38AB, UW Cet AB lower main sequence of the Hyades cluster is well repre-

TABLE 9 VISUAL BINARIES IN THE HYADES SUPERCLUSTER

o (km s~1) n (mas) XV P.V. HD (pc) (kmtot s~1) Obs. Comp. Cluster Hip. p ADS HIP (km s~1)NOTES 38...... 4 43.7 ]0.1 ]0.7 96.8 85.10 2.14 48 473 [1.2 6114 ...... 60 46.2 ]5V ]8.7 8.2 9.68 1.01 862 4911 [3.7 BD ]1¡194 ...... 35 44.6 Var. ]12.0 12.5 11.43 1.69 864 4886 [4.5 UV Ceta ...... 1 43.5 Var. ]11.1 358.0 (367) [0.7 23588 ...... 9 43.9 ]32.9 ]28.8 46.9 45.95 1.41 2756 17544 [4.5 27130 ...... 42 45.4 ]38.1 ]38.0 21.9 21.40 1.24 . . . 20019 ]1.5 1, 2 27383 ...... 39 45.25 ]36.8 ]38.4 23.5 23.27 1.34 3135 20215 ]1.7 1 27691 ...... 43 45.45 ]37.9 ]38.6 21.1 21.45 2.96 3169 20440 ]0.2 1, 3 27991 ...... 42 45.4 ]38V ]39.0 22.1 21.47 0.97 . . . 20661 [0.5 1 27989 ...... 40 45.3 ]41.0 ]38.7 23.3 23.08 1.22 3210 20686 ]0.2 1 28363 ...... 41 45.35 ]42V ]39.4 22.5 20.58 1.74 3248 20916 ]1.1 1, 4 28485 ...... 40 45.3 Var. ]39.3 23.0 22.93 1.25 3264 20995 ]0.7 1 30810 ...... 41 45.35 ]39.0 ]41.4 22.5 20.15 1.42 3475 22550 ]1.0 1 46780 ...... 36 45.15 . . . ]42.2 26.9 27.72 1.97 5234 31568 ]3.2 89376 ...... 24 44.6 ]23.1 ]23.9 20.2 16.86 2.13 7721 50524 [0.6 Wolf 424a ...... 0 43.5 [3: [2.0 190.6 210.0 [0.3 177475...... [15 42.8 Var. [36.3 62.0 55.89 1.94 . . . 93825 ]0.2 186602...... [53 41.1 . . . [22.6 14.6 17.24 1.16 . . . 97508 [1.0 213973...... 23 44.55 [2V [2.6 14.7 13.11 0.56 16057 111314 0.0 220278...... [15 42.8 [14V [12.4 13.9 13.75 1.05 16708 215404 ]4.3

NOTES.È(1) Hyades cluster; (2) V818 Tau, double-lined eclipsing binary (P \ 5.61 days); (3) component A is spectroscopic binary, P \ 4 days; (4) component B is spectroscopic binary, P \ 21.25 days. a Proper motions from Hipparcos (ESA 1997) except for UV Cet and Wolf 424, for which proper motion is the mean of results from parallax determinations. No. 1, 1998 AGE RANGE OF HYADES STARS 291

TABLE 10 COMPONENTS OF SUPERCLUSTER BINARIES

Pa HD VB[VMV (yr) (mas) Reference 6114A ...... 6.75 0.23 ]1.32 450.0 816 1 6114B ...... 8.05 0.30 ]2.62 BD ]1¡194A ...... 10.27 0.77 ]5.76 61.1 230 2 BD ]1¡194B ...... 10.27 0.77 ]5.76 23588A ...... 8.30 0.97 ]6.66 425.0 2761 3 23588B ...... 11.00 (1.50) ]9.36 27130A ...... 8.44 0.71 ]5.14 5.61 days . . . 4 27130B ...... 10.74 1.19 ]7.44 27383A ...... 7.13 0.48 ]3.99 89.47 583 5 27383B ...... 8.63 0.71 ]5.49 27691AA@ ...... 7.35 0.50 ]3.97 239.1 1153 6 27691B ...... 8.50 0.65 ]5.12 27991A ...... 7.20 0.50 ]3.92 6.28 98.4 6 27991B ...... 7.20 0.50 ]3.92 27989A ...... 8.06 0.65 ]4.90 27.59 264.1 6 27989B ...... 8.56 0.71 ]5.40 28363A ...... 7.10 0.52 ]3.86 39.93 382.3 6 28363BB@ ...... 7.70 0.54 ]4.46 28485A ...... 5.70 0.29 ]2.51 180.0 1000 7 28485B ...... 7.94 0.60 ]4.75 30810A ...... 7.51 0.56 ]4.27 16.281 191.8 6 30810B ...... 7.51 0.56 ]4.27 46780A ...... 7.14 0.57 ]4.29 118.9 850 8 46780B ...... 8.71 0.85 ]5.86 89376A ...... 9.41 0.80 ]5.94 460.0 1350 9 89376B ...... 10.27 1.06 ]6.80 177475A...... 5.06 0.52 ]4.02 118.55 2000 2 177475B ...... 5.06 0.52 ]4.02 186602A...... 8.05 0.51 ]3.87 13.94 309 10 186602B ...... 8.05 0.51 ]3.87 186602C...... 10.59 0.98 ]6.41 213973A...... 6.84 0.32 ]2.68 215.0 772 11 213973B ...... 6.84 0.32 ]2.68 220278A...... 5.66 0.19 ]1.38 65.0 350 10 220278B ...... 6.36 0.21 ]2.08 REFERENCES.È(1)Heintz 1964; (2) Eggen 1965; (3) Hopmann 1995; (4) Schiller & Milone 1987;(5) McAlister 1990; (6) Peterson & Solensky 1988; (7) Baize 1980; (8) Heintz 1996; (9)Heintz 1960; (10) Eggen 1984; (11) Heintz 1993. sented by The total mass obtained from the orbital elements in Table 10and the cluster parallax in Table 1, MI \ 4.56(R[I) ] 3.95 mag , (6) ; \ a3/P2n3 M_ , (7) and this is the origin of the values ofMI(phot) in Table 11. mass The mean di†erence MI(clus) [MI(phot) \]0.04 ^ 0.06 is listed inTable 12 (““ Obs. ÏÏ). The values obtained from the mag. The orbit for HD 38AB is obviously still indetermi- luminosities of the individual components and the stellar nate, but the well-observed systems UV Cet and Wolf 424 model with t \ 8 ] 108 yr and Z \ 0.025(Castellani et al. give reliable masses for stars that are near the end of the 1992) are labeled ““ Model ÏÏ in the table. Two systems in hydrogen-burning main sequence: UV Cet, 1 ; \ 0.13 which one component is known to be a spectroscopic M ; Wolf 424, 1 ; \ 0.10 M . 2 mass binary, HD 27691AA@B and HD 28363ABB@, indicate that _ 2 mass _

TABLE 11 LOW-LUMINOSITY SUPERCLUSTER BINARIES

MI Pa STAR IR[ICluster Phot. (yr) (mas) REFERENCE HD38A ...... 7.27 0.71 ]7.20 ]7.19 500 6000 1 HD38B ...... 7.31 0.71 ]7.24 ]7.19 BD ]44¡4548 ...... 8.03 0.85 ]7.96 ]7.83 UVCetA ...... 9.05 1.70 ]11.80 ]11.70 26.52 2.06 2 UVCetB...... 9.05 1.70 ]11.80 ]11.70 Wolf 424A ...... 9.73 1.58 ]11.13 ]11.16 16.0 715 3 Wolf 424B ...... 9.73 1.58 ]11.13 ]11.16 HD 186602C ...... 9.71 0.343 ]5.54 ]5.51 REFERENCES.È(1)Heintz 1996; (2) Worley & Behall 1973; (3) Heintz 1993. 292 EGGEN

TABLE 12 TOTAL MASSES

; (M ) ; (M ) mass _ mass _ HD Obs. Model NOTES HD Obs. Model NOTES

BD ]1¡194AB ...... 1.67 1.88 28485AB ...... 2.54 2.76 1 23588AB ...... 1.14 1.23 30810AB ...... 2.34 2.40 1 27130AB ...... 1.85 1.78 1 46780AB ...... 2.23 2.14 27383AB ...... 1.91 2.26 1 89376AB ...... 1.41 1.72 27691AA@B ...... 2.85 2.32 1, 2 177475AB ...... 2.40 2.46 27991AB ...... 2.25 2.57 1 186602AB ...... 2.32 2.60 27989AB ...... 1.91 2.09 1 213973AB ...... 3.13 3.16 4 28363ABB@ ...... 3.08 2.50 1, 3 220278AB ...... 3.78 3.92

NOTES.È (1) Hyades cluster; (2) component A is spectroscopic binary, P \ 4 days; (3) component B is spectroscopic binary, P \ 21.2 days; (4) uP \ 215 yr, orbit uncertain. the unseen companion has approximately 0.5 solar masses. Although the masses are of interest in themselves, they The errors are probably equally distributed between the are included here because the extreme dependence of the components, so the dispersion for the mass of a single com- mass determination on the parallax further conÐrms the ponent is less than 10%. parallaxes adopted here.

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