Publications of the Astronomical Society of the Pacific 87: 17-36, 1975 February

DDO INTERMEDIATE-BAND PHOTOMETRY OF MOVING-GROUP STARS

ROBERT J. BOYLE AND ROBERT D. McCLURE* Yale University Observatory Received 1974 October 2

G and Κ giant stars in several of Eggen's moving groups have been observed on the DDO system. The cyanogen strength and absolute magnitude calibrations of the system are used to discuss the assignments of the observed stars to moving groups. We are able to confirm the assignment of some 50% of the members of the Hyades moving group and thus to segregate out a more homogeneous sample of Hyades group stars. These stars can be used to recalibrate intrinsic Hyades giant sequences. Less firm conclusions are reached concerning the other, older, groups discussed. Key words: moving groups — abundances — late-type stars

I. Introduction yrs), contain many groups, among them the Wolf During the past 16 years, Eggen has presented 630, 61 Cygni, ζ Herculis, σ Puppis, e Indi, and an extensive and impressive body of evidence for η Cephei moving groups. The old-disk stars the existence of moving stellar groups. These share the velocity distribution of the evolved F streams of stars possessing similar space motions and G stars lying between the Hyades and are thought to result from the breakup of clusters NGC 188 sequences in the {Mv,B—V) plane and associations of stars sharing a common origin (Eggen 1973c). Near the boundary between the in space and time (Eggen 1958). Eggen has iso- old-disk stars and the halo population lies the lated moving groups in four stellar kinematic Arcturus moving group with an age comparable populations labeled as very young, young, old- to NGC 188, whose stars travel in galactic orbits disk, and halo. The youngest of these popula- of mean eccentricity e = 0.45 (Eggen 1971α, tions, that of the very young-disk stars, is defined 1974α). The halo population stars are those by the velocity distribution of the early Β stars which travel in orbits with e > 0.5. Among the (Eggen 1973ö) and contains two groups, the halo population, the Groombrige 1830 group of Pleiades group of stars that share V = — 25 km high-velocity stars, whose galactic orbits have a sec-1 with the Pleiades cluster, and a group with mean e = 0.83, has been isolated by Eggen and V = —18 km sec-1 (here U, V, W are the usual Sandage (1959). components of space motion with respect to the To the extent that the group assignments can sun, V being the velocity component in the direc- be made reliably, the concept of moving groups tion of galactic rotation). Stars of this very young- is one of great utility, yielding distance moduli, disk population are thought to be from 2 to space motions, and population information for 7 X 107 years old. The young-disk stars are large numbers of "field" stars. For example, those with ages between that of the very young- Eggen has used the red giants of the Hyades disk population and that of the Hyades cluster moving group to define intrinsic sequences in 8 (5 to 8 X 10 yrs, Eggen 1973b). Among the the (Mbol, R—I) plane and the {U~B, B— V) and moving groups of this population are the Hyades ((7—B, R—l) two-color diagrams (Eggen 1966, and Sirius moving groups. The old-disk-popula- 1972α, 1974&). The (Mbol,R—I) calibrations for tion stars, with ages between that of the Hyades the Hyades and old-disk groups have been used cluster and that of NGC 188 (some ~10 X 109 by Eggen {1973b,c) to obtain distances in discussions of the kinematics of the immediate solar ♦Visiting Astronomer, Cerro Tololo Inter-American Observatory and Kitt Peak National Observatory, which neighborhood, while the (C7—Β,Β—V) relation are operated by the Association of Universities for Re- has been employed to obtain ultraviolet excesses search in Astronomy, Inc., under contract with the Na- for giant stars (e.g., Eggen 1972b; McClure 1970, tional Science Foundation. 1974). Group membership has been used to dis-

© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 18 BOYLE AND McCLURE cuss the absolute magnitudes of variable and II. Observational Data and peculiar stars such as δ Scuti, RR Lyrae and R Reduction Techniques Coronae Borealis variables (Eggen 1969α, 1970α; Eggen and Sandage 1959; Bessel 1967), Am and For G and Κ giants, observations through the Fp stars (Eggen 1970a), and Bau and R-type 48, 45, 42 and 41 filters of the original DDO stars (Eggen 1972c). Eggen has also made use intermediate-band system (McClure and van of moving groups in a discussion of the empirical den Bergh 1968) yield information on tempera- mass-luminosity relationship (Eggen 1963α). ture, luminosity, and cyanogen abundance (Mc- It is the aim of this paper to investigate the Clure 1973). The original cyanogen index, δ Cm, reliability of group assignments for G and Κ was found to have a residual dependence on giants through the use of the metallicity and abso- luminosity by Janes (1972,1974a) and was re- lute magnitude calibrations of the David Dunlap calibrated by him, yielding a new index δ CN, Observatory (DDO) photometric system (Mc- used here, δ CN is defined as the difference be- Clure 1973). Breger (1968) has used Strömgren tween the observed cyanogen band strangth, four-color photometry to conclude that from C(41-42) and the mean value for solar neighbor- 40% to 60% of the main-sequence A and F stars of hood stars of similar C(42-45) and C(45-48) the Hyades moving group may be incorrectly indices (that is, similar surface temperatures and assigned to the group. Eggen (1970α), however, gravities). Janes (1974a) has also been able to disputes this result, attributing the large spread use the colors C(45-48) and C(42-45) to cali- in πΐγ found by Breger to the presence of Am and brate DDO photometry in terms of absolute Fp stars in the group and to a luminosity effect visual magnitude, Mv. In the process of the in ml for some stars. Williams (1971) has also δ CN and Mv calibrations, the Copenhagen inter- uséd narrow-band spectrophotometer indices to mediate-band indices of Dickow et al. (1970) investigate the homogeneity and metal abun- were transformed to DDO indices (Janes 1972, dance in moving groups. He found that a major- 1974a) for a large number of stars, and we shall ity of Hyades stars studied had [Fe/H] values use these transformed indices to supplement similar to the Hyades cluster, but that other directly observed DDO data. groups were less homogeneous. We believe The new DDO observations obtained for this DDO photometry is well suited to a reinvestiga- investigation were made with the Yale 40-inch tion of this question for Hyades and perhaps (102-cm) reflector at Bethany, Conneticut, with a other group giants. two-channel pulse-counting photometer, and at In the discussion of the metallicity of the group either Kitt Peak National Observatory with 16- red giants we will implicitly assume a chemical inch and 36-inch reflectors and a one-channel homogeneity comparable to that found in clus- current-integrating photometer, or at Cerro ters as a requisite for group membership. It Tololo Inter-American Observatory with a 36- should be bom in mind, however, that the G and inch reflector and a one-channel pulse-counting Κ giants of some clusters may show evidence of photometer. Standard stars from McClure and a significant spread in metallicities through spec- van den Bergh (1968) (for Kitt Peak and Bethany tral peculiarities (e.g., Ban stars in NGG 2420 observations) or from a new list of equatorial (McClure, Forrester, and Gibson 1974), carbon standards being prepared by McClure (for Cerro stars in ω Centauri (Wing and Stock 1973)) and Tololo observations) were also observed each perhaps through a scatter shown by the color- night so that transformations to the original magnitude diagram of the giant branch. For DDO system were obtained. Mean extinction example, see discussions of NGC 188 (McClure coefficients were applied. In averaging observa- 1974) and ω Gen (Cannon and Stobie 1973). tions of the same star, a few results on nights of Also see the discussion of variations in G-band poor quality at Bethany were given half weight. strengths among giant stars in M 92 by Zinn Table I lists the sources of the data and standard (1973). With this reservation in mind, the range errors of the mean for the three colors of the of the DDO metallicity parameter, δ CN, to be DDO system for a star observed on three nights, expected in the general field, in clusters, and in both for new observations and observations from moving groups will be discussed in section III. previous investigations.

TABLE I SUMMARY OF DDO PHOTOMETRY

Standard Errors (3 Observations)

Rpf Reference ^ 0(45-48) 0(42-45) 0(41-42)

McOlure and van den Bergh (1968) 1 0^007 0^006 0^007

McOlure (1970) 2 0.004 0.005 0.005

Janes and McClure (1971) 3 0.006 0.005 0.005

Goodenough (1969) 4 0.012 0.016 0.013

Janes and McClure (unpublished) 5 0.007 0.005 0.005

Janes (1972) 6 0.005 0.005 0.005

Bethany (this paper) Β 0.008 0.009 0.007

Kitt Peak (this paper) KP 0.005 0.00M- O.OOM-

Cerro Tololo (this paper) CT 0.002 0.002 0.002

Dickow, et al. (1970)-Transformed C 0.007 0.012 0.011

Average of above 0^007 0^007 θΤθ07

III. DDO Photometry of Field and Cluster Stars Praesepe clusters (McClure and van den Bergh (1968), Osborn (1971), Janes (1972), Janes and The distribution of δ CN for a random sample McClure (1971), and Janes and McClure (un- of G and Κ giants that have directly observed published)), NGC 2477 (Hartwick, Hesser, and DDO indices and that lie within a 200 pc radius McClure 1972), NGC 752 (Goodenough 1969), of the sun is shown in Figure 1. Data have been NGC 7789 (Janes 1972), NGC 2420 (McClure, taken from a compilation by Janes (1972), but Forrester, and Gibson 1974), and M 67 (Janes any original sources where stars were selected in 1974b) are shown in Figure 3 arranged approxi- a nonrandom fashion have not been used in mately according to age. If we ignore the low Figure 1. The width of this distribution as mea- δ CN stars in NGC 2477 (Eggen and Stoy (1961), sured by the standard deviation is ± 0^43. nos. 201, 882, and 959), which are very likely In order to compare the photometric index field stars as judged from their position in the δ CN with the spectroscopic description "strong cluster and in the cluster C-M diagram and keep CN" and to thereby place the δ CN distributions in mind the effect of large and possibly variable of clusters and groups in better perspective, the reddening on the NGC 7789 and NGC 2477 δ CN distribution of a sample of spectroscop- indices, we may conclude that the intrinsic spread ically selected strong CN stars (Schmitt 1971) is of δ CN in most clusters is no larger than about shown in Figure 2. DDO photometry for these ±0^02 (standard deviation). Note, however, in stars has been taken from McClure (1970). the most extreme case, that of NGC 188 (McClure The δ CN distribution for the Hyades and 1974), the spread of δ CN values is ±4 0^04.

-0.10 -0.05 0.0 +0.05 +0.10

SCN

Fig. 1 — Histogram of number of stars per 0ηΌ1 interval of the DDO metallicity index δ CN for a random sample of 190 field G and Κ giants within 200 pc of the sun.

0.0 +0.05 +0.10 +0.15

SCN

Fig. 2 — δ CN distribution for a sample of 128 spectroscopically selected "strong CN" stars.

IV. The Hyades Moving Group with this value of V with the local standard of rest (Eggen 1969α, 1973c). In fact, a focusing Eggen,s Hyades moving group (V = —16.8 effect noted by King (1961) and Wolley (1961, km sec-1, [7 = -f 30 to +50 km sec-1; Eggen 1965) brings stars with the same V motion as the 1972α) is located in a well-populated region of local standard of rest back to the solar neighbor- the U,V velocity plane, where stars ranging in hood each ~2 X 108 yrs. Thus the Hyades age from the very young-disk population through moving-group stars have made some two cir- the Hyades-group stars themselves to stars of the cuits of the galaxy (Eggen 1969α). It should be old-disk population, are found (Eggen 1973a,fo,c). noted further that this focusing mechanism tends Eggen attributes this clumping of velocities near to clump stars at particular values of V regard- —17 km sec-1 to the isoperiodicity of stars less of the spread in their initial U vectors.

SCN Fig. 3— 8 CN distribution for giant stars in several galactic clusters. Clusters are arranged approximately in order of increasing age. Means and standard deviations of the distributions of SCN are Hyades-Praesepe: -fOnO7 ± O^Ol; NGC 2477: +(Γ08 ± (TOS; NGC 752; -(TOI ± 0ηΌ1; NGC 7789: +0ηΌ0 ± 0ηΌ2; NGC 2420: -0^06 ± 0ηΌ2; Μ67: +0ηΌ3 ± 0^02.

Using all available luminosity estimates, 82 were selected as group members on the basis Eggen (1972α) has derived space motions of of luminosities derived by forcing V = —16.8 2860 red giants in the Catalogue of Bright Stars km sec-1 (Eggen 1972α) and are listed in Table I (Hoffleit 1964). From the 114 stars whose U,V of that paper. The available DDO observations values were thus found near that of the Hyades, for the G and Κ stars in Eggens list, together

© Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 22 BOYLE AND McCLURE with data for the group member HD 12402 assume that the 25 stars with δ CN ^ 0^03 are (Eggen 1970¾) are presented in Table Ha, while most likely spurious members of the Hyades Table lib contains data for stars listed as pos- group. The spread of δ CN values for the 25 re- sible members either by Eggen {1970b) or maining stars is ±0,ΐΌ2, and hence they show Eggen (1972«). The first four columns contain the degree of chemical homogeneity to be ex- the HD number (followed by an asterisk if the pected in a true group as judged from experi- star is a member of the Hyades or Praesepe clus- ence with cluster δ CN distributions (§ III, ters) and the three DDO indices of the star. above). Hereafter these 25 stars with δ CN > The number of observations and the source of 0^03 will be referred to as true Hyades group the observations are listed in the fifth column. stars. (Note that if the field-star distribution in Numbered references are to prior investigations Fig. 4b is renormalized to the 25 spurious mem- (see Table I), while new observations are bers, it appears likely that at most 1 or 2 of the labeled Β (Bethany, Conn.), KP (Kitt Peak), or true group stars remain incorrectly assigned.) CT (Cerro Tololo). Indices transformed from the To demonstrate that the separation of group Copenhagen Catalogues (Dickow et al. 1970; stars into the two subsets mentioned above at Janes 1972) are referenced C. The sixth and δ CN = 0^3 is not caused by any peculiarity of seventh columns of Table II contain the derived the DDO cyanogen index for these stars, but quantities δ CN and Mv (DDO) obtained from rather is a manifestation of a genuine difference the calibrations of Janes (1972, 1974a). The last in element abundance, ultraviolet excesses were four columns of Table II contain UBV data from computed for the stars in Table Ha using the Eggen (1970α), Eggen (1972α), or Eggen (1974b), mean two-color relation for the Hyades group and the values of Μυ derived by Eggen assuming giants (Eggen 1966) V = —16.8 km sec~1 for each star. As the DDO indices are little effected by red- {U — Β) = 2.0(8-V) - in6 . (1) dening (McClure and Racine 1969; McClure 1973) and sls most of the group stars treated Reddenings found by Eggen (1972α) from UBV here have £(5-^^)^0^05 (Eggen 1972α; see photometry of nearby early-type stars were em- also Eggen 1963b; FitzGerald 1968), reddening ployed, reduced by a factor of 0.9 (see Femie corrections have not been applied to the DDO 1963; Hartwick and McClure 1972). A redden- data for moving group stars. ing slope of E{U—B)IE{B—V) = 0.9 was as- The δ CN distribution of the Hyades group sumed for stars with (B— V) = 1^2 and this value stars in Table lia is shown in Figure 4a where was increased to 1.0 for the reddest stars (again the Hyades and Praesepe cluster giants with see Fernie 1963; Hartwick and McClure 1972). DDO indices are indicated by hatched areas. The true group stars with Hyades cluster-like In Figure 4b the δ CN distribution of the moving δ CN values show no mean ultraviolet excesses group stars is compared with the field-star dis- over relation (1) having a mean 8{U — B) = tribution of Figure 1. Both distributions have 0^00 ± 0^03 (s.d. one star) while the spurious been smoothed by averaging adjacent bins and group members with δ CN = 0^3 show an ex- the field-star distribution has been normalized cess of δ ((7-β) = +0n)4± 0m05 (see Fig. 5). by the ratio of the number of group stars (50) to Furthermore, the stars having negative cyanogen the number of field stars (190). The group stars anomalies only, have a still larger mean excess, taken alone show a definite peak at δ CN δ ((7-B) = +0^7 ± O^XM. Hence the spurious — 0^05, near the peak of the Hyades-Praesepe group stars give every indication of being cluster stars. However, the δ CN distribution of genuinely metal poor with respect to the tnie Figure 4a shows a "tail" or second peak extend- group stars, and may well belong to a different ing below δ CN = the average value for and perhaps older stellar population. This is field giants. In fact, the impression given by not surprising considering the clumping of old- Figure 4b is that there is a division at δ CN = disk stars in the {U,V) velocity plane shown by 0^03 and that stars with δ CN below 0^3 show Eggen (1973c, Fig. 2) near the Hyades value of a distribution not unlike that of a random sample V. of field stars. In what follows we shall therefore The isolation of a true group of Hyades giants

TABLE II HYADES GROUP STARS

C45-48 CI42-I+5 CUl-i+2 S ,n ¿fCN My (DDO) B-V U-B Mv (GROUP) Spectra a) Likely Members 12402 lTl55 0.859 0T253 Β , 2 +0.106 +1.06 6m5 +1.00 K1 III 13818 1.185 0.87 6 0.188 Β,4 -0.010 +0.70 6.3 +1.55 G9 III 15889 1.191 0.865 0.19 4 CT ,2 -0.015 +0.26 6.30 +1.01 +0.74 +0.94 G8 III 17228 1.153 0.785 0.180 Β,2 +0.013 +0.12 6.32 +0.94 +0.62 +0.00 G8 III 17459 1.255 1 .014 0.249 Β,2 -0.025 +0.64 5.87 +1.24 +1 .19 +0.18 gKl 1947 6 1.171 0.852 0.235 3,3 +0.057 +0.51 3 .80 +0.98 +0.83 +1.17 KO III 19787 1.194 0.893 0.255 Β,3 +0.045 +0.52 4.35 +1.03 +0.86 +1.05 K2 III 26703 1.234 0.952 0.314 Β ,3 +0.055 -0.04 6.24 +1.14 +1.08 +0.53 KO 27304 1.214 0.959 0.220 CT ,2 -0.009 +1.12 5.49 +1.11 +1.00 +0.58 gKi 27371* 1.174 0.827 0.262 ** +0.071 -0.27 3.65 +0.99 +0.81 +0.63 KO III 27697* 1.180 0.826 0.268 +0.067 -0.65 3.76 +0.99 +0.82 +0.63 KO III 28305* 1.188 0.849 0.286 +0.078 -0.53 3.54 +1.01 +0.87 +0.56 KO III 28307* 1.161 0.811 0.229 ** +0.057 +0.19 3.83 +0.95 +0.72 +0.78 KO III 29139 1.395 1.365 0.230 1,3 0.85 +1,54 +1 .92 -0.45 K5 III 34029 1.084 0.703 0.117 Β,3 0.05 +0.80 +0.43 -0.75 G8 III+F 35620 1 .358 1.198 0.411 2,3 +0.094 -0.81 5.08 +1.39 +1.66 -0.39 gK3p 35991 1.194 0.870 0.258 Β , 3 ;CT,2 +0.044 -0.13 6.10 +1.02 +0.86 +0.57 gG7 39007 1.127 0.729 0.197 3,3 5.7 9 +0.87 +0 . 62 +1 .44 gG3 40827 1.210 0.956 0.316 2,3 +0.093 +0.69 6.34 +0.69 G8 43023 1.142 0.792 0.135 Β , 1 ;CT , 2 -0.011 +1.01 82 +0.94 +0.64 +1.52 gG7 50384 1.143 0.806 0.184 Β,3 +0.041 +1.07 32 +0 .95 +0.70 +1.70 KO 64152 1.142 0.818 0.202 Β,3 +0.065 +1 .1 7 62 +0.96 +0.70 +1 .33 gG8 65273 1.292 1.127 0.303 CT ,2 +0.012 +0.56 62 +1.30 +1 .44 -0.12 gK5 71369 1.131 0.722 0.138 2,3 35 +0.85 +0.51 -0.40 G5 III 71952 1 .164 0.896 0.152 Β,3 -0.004 +2 .02 24 +0 . 44 KO 73171 1 .240 0.987 0.226 Β,3 -0.035 +0.71 93 +1.16 +1 .05 -0.13 SK' 73598* 1.166 0.819 0.238 C ,4 +0.060 +0.08 60 +0.96 +0.71 +0.50 KO III 73665* 1.172 0.824 0.263 3,3 +0.075 -0.23 6.40 +0.98 +0.83 +0.30 KO III 73710* 1.182 0.865 0.283 5,3 +0.088 +0.08 6.42 +1 .02 +0.90 +0.32 KO III 82350 1.194 0.944 0.203 CT , 2 +0.005 +1.56 5.48 +1 .08 +0 .98 +0. 62 SK2 94247 1.314 1 .113 0.277 Β ,4 -0.039 +0.21 5.09 +1.36 +1 .52 -0.37 K3 III 94402 1 .165 0.815 0.226 KP, 3 +0.048 +0.11 5.44 +0.97 +0.79 +0.7 6 gG6 99322 1.174 0.849 0.183 KP, 3 -0.001 +0.58 5.27 +1.00 +0.74 +0.89 RKO 100006 1.192 0.906 0.194 6,3 -0.009 +1.19 5.53 +1.07 +0.82 +0.50 rKO 100407 1 .158 0.807 0.219 KP, 3 +0.051 +0.29 3 .55 +0.95 +0.72 +0.12 G7 III 101112 1 .198 0.929 0.256 Β,4 ;KP , 2 +0.048 +1.02 6.16 +1.08 +0.96 +0.3 8 Κ' III 109217 1.155 0.801 0.207 KP. 3 +0.042 +0 .40 6.30 +0.96 +0.70 +0.74 ñG7 110014 1.279 I .027 0.399 3,3 +0.101 -0.75 4.66 +1.26 +1.36 -0.25 K2 III 113226 1.144 0.798 0.213 2,3 +0.067 +0.75 2 .84 +0.94 +0.74 +0.46 G9 III 116976 1.213 0.899 0.332 3,3 +0.092 -0.35 4.75 +1.10 +1.06 +0.15 K! III 120084 1.170 0.848 0.226 Β,3 +0.049 +0.52 5.9 +1 .12 gG7 120452 1.194 0.897 0.241 KP, 3 +0.032 +0.73 4.96 +1 .06 +0 .91 +0.34 Ki III 131530 1.177 0.83 6 0.190 6,3 -0.004 +0.12 5 .80 +0.97 +0.7 5 +0.72 gG7 136422 1.388 1.325 0.222 KP, 3 -0.053 +0.08 3.56 +1 .53 +1 .85 - 0 . 2 6 Κ5 III 138852 1 .174 0.832 0.170 6,3 -0.019 +0.30 5.74 +1.14 gG5 ' 143209 1.205 0.939 0.2 51 Β,3 +0.032 +0.91 6.28 +1 .43 KO 143787 1 .261 1.070 0.274 KP, 2 +0.001 +0.88 5.01 +1.24 +1 .23 +0 . 49 fiK5 144046 1 .173 0.826 0.239 Β,3 +0.050 -0.12 6.08 +0.9 6 +0.75 + 1 .22 G9 III · : 1487 86 1.154 0.7 86 0.236 Β . 2 ; 3 ,3 +0.067 -0.19 4.27 +0.93 +0.72. +0.47 G8 III 157527 1.138 0.786 0.203 Β,3 +0.06L1 +0.75 5.85 +0.94 +0.6 7 +1 .22 c^r;7 1 627 3'! 1.165 0.839 0.187 Β,3 +0.015 +0.69 6.40 +1 .23 KG III 171759 1.240 0.953 0.184 CT , 2 -0.083 +0.37 4.01 +1.13 +1.02 +0 .63 Κ2 III 1M 2()35 1.199 0.920 0.176 Β,3 -0.036 +1.23 6.32 +0.Π9 κι TU 189310 1.400 1 .3 64 0.273 Ι,Ί 3.55 +1 .57 +1 .93 -1.17 Κ5 III 190252 1 .132 0.7H0 0.1 16 Β,4 -0.016 +1 .37 6.33 +0.88 +0.54 +1 .07 G8 III 190608 1.184 0.917 0.213 Β .2 +0.026 +1.45 5.09 +1.07 +0.95 +0.M5 K2 III 199870 1.159 0.841 0.220 Β , 2 ; 6 ,3 +0.061 +0.78 5.55 +0.98 +0 .81 +0. 71: G8 III 202951 1 .428 1.358 0.218 Β,3 6.16 -0.44 Κ 5 217382 1.352 1 .230 0.304 Β,4 +0.008 +0.09 4.72 +1.42 +1 .70 -0.25 KM 11 I 218670 1.189 0.840 0.285 CT , 2 +0.073 -0.92 3.88 +1 .01 +0.87 +0.25 KO III 220572 1 .201 0.907 0.232 CT , 2 +0.013 +0.76 5.64 +1 .05 +0.97 +0.74 fiK2 ' . 222493 1.172 0.840 0.273 Β,4 +0.090 +0.06 5.89 +0.98 +0.78 +0.28 gG9 223252 1.161 0.803 0.194 Β,4 +0.020 +0.21 5.48 +0 .94 +0.70 +0.70 G8 III b) Possible Hyades Group Members 97989 1.206 0.932 0.236 +0.015 +0.91 5.82 +1.27 RKO 147 677 1.162 0.840 0.237 +0.072 +0.58 4.83 +0.98 +0.80 +1.83 KO III 199223 1.092 0.695 0.160 6.05 +0.81 +0.48 +0.9 sgG6 204771 1.162 0.853 0.207 +0.045 +0.94 5.24 +0.98 +1.2 KO III 222683 1.154 0.817 0.225 Β ,4 +0.067 +0.59 6.40 +0.95 +1.2 gG7 * Hyades or Praesepe Cluster member. ** Weighted mean of McClure and van den Bergh (1968) , Osborn (1971) , and unpublished observations by McClure.

α 10.

5 1 ■ 1 1 1 1 1 1 1 1 1 III . Λ b - \ r \\ V\\ \ / νΛ Vv A V \ / νΛ \v r ^ J Χ \/ xV\ / 'Λ \\ // \ \\\ \ / / \ / \ \\\ \/v \ ΧΧνΛ \ ^ \\x \\ -1 — ^ J i\L^i 1 1 1 1 1 ' ' ' 1 1 1 Γ ■ >1 ·\|-Ι, -0.10 -0.05 0.0 +0.05 +0.10

SCN

Fig. 4 —(a) 8 CN distribution of 50 Hyades moving group stars and seven Hyades-Fraesepe cluster stars (hatched area), (b) Solid lines represent the same distribution as in (a) but smoothed. Dashed line represents the field star distribution of Figure 1, smoothed and normalized by the factor 50/190.

from Eggens original list allows a recalibration stars (McClure 1970) with 0^03 ^ δ CN < (P08. of equation (1). As can be seen in Figure 5, the These stars may indicate that either the slope of slope of any new relation is likely to depend the two-color relation for giants is still steeper, heavily on the colors of but two stars, HD 35620 perhaps near 2.2, or that the true two-color rela- and HD 110014. A search of the catalogues of tion is nonlinear. Finally it should be noted that Blanco et al. (1968), McClure (1970), and Eggen the use of equation (2) does not significantly (1972α) shows a substantial spread in the pub- modify the mean ultraviolet excesses quoted lished colors for HD 110014, and a somewhat above and that the δ (U—B) value obtained for smaller spread for HD 35620, hence any recali- stars near (B—V)= 1^0 (the location of the bration should be considered provisional. A clump of most old galactic clusters) is the same weighted mean of the results of least-squares fits using either equation (1) or (2). to the colors in Table II and those in Blanco et al. In addition to examining metal-abundance (1968) and McClure (1970) yields criteria, one can also compare calibrations of absolute magnitudes of the group stars. The {U- B) = 2.1(ß— V) - 1^26 . (2) approximate agreement, in the mean, of group In Figure 5 both equations (1) and (2) are Mv estimates with those from any other source shown as well as true (filled circles) and spurious does not constitute a demonstration of the reli- (open circles) Hyades group stars. By way of ability of group assignments, since trigonometric, comparison. Figure 6 shows a sample of spectro- spectroscopic, and photometric parallaxes were scopically selected strong CN class III G and Κ employed in the initial selection of group mem-

Fig. 5 —Two-color diagram for the stars in Figure 4 Fig. 6 — Two-color diagram for stars from Figure 2 hav- having 0^03 < 8 CN ^ 0nill (filled circles) and 8 CN ^ ing Hyades-like cyanogen strengths. Solid line repre- 0ηΌ3 (open circles). Note that the open circles lie on sents the calibration adopted here. the average +0ηι04 above the solid line which represents the calibration of Eggen (1966). The dashed line repre- (GROUP) — M (DDO), the stars in Figure 7a sents a calibration based on the filled circles and adopted v here. have a mean ΔΜυ = +0^39 ± 0^46 (standard deviation, one star), a spread comparable to that bers. However, an examination of the spread in expected from errors in Mv (DDO) alone (Janes the agreement can be helpful. Figure 7a and b 1974a), while the stars in Figure 7b indeed show compares the DDO absolute magnitude Mv a larger spread, having in the mean ΔΜυ = (DDO) with Eggen s group absolute magnitudes — (^17 ± 0^5. We interpret this increased based on forcing V = —16.8 km sec-1 for the spread to be due to the process of forcing the group stars (obtained from distance moduli, V spurious group members to V = —16.8 km sec-1, magnitudes, and values of E(B—V) in Eggen a velocity they share only approximately. -1 (1972α, Table I); At;=3E(B-V) assumed). The value V = —16.8 km sec imposed on Figure 7a shows the comparison for the 25 true the Hyades group stars by Eggen is based on a group stars, 7b that for the spurious group stars. space motion for the Hyades cluster correspond- Hyades and Praesepe cluster stars are also indi- ing to a mean distance modulus of 3^5 for the cated. We note that the true Hyades group stars cluster. If we assume instead that the Hyades lie on a relatively tight sequence some 0^4 above cluster lies at a distance modulus of 3^2 (Van the Mv (DDO) = Mv (GROUP) line while the Altena 1969,1974) from the data in Eggen (1972α, spurious group stars are more scattered about Table I) relating changes in V velocities with that line. In fact, if we define ΔΜν = Μυ changes in distance, we estimate that V is closer

MV(6R0UP)

Fig. 7 — (a) The DDO photometric absolute magnitude Mv (DDO) is plotted against the absolute magnitude obtained from group membership for the 25 Hyades group stars in Figure 4a with 0Φ03 < δ CN =¾ 0Φ11. Praesepe cluster members are shown as plus signs, Hyades cluster members as crosses. The solid line represents Mv (DDO) = Mv (GROUP), (b) The same diagram for the 25 "spurious" group members, i.e., those with δ CN 0ip03. to —18.1 km sec-1 for the cluster. From this The available DDO data for the Wolf 630 value of V, a new set of Mv (GROUP) values may group G and Κ giants listed by Eggen (1969α, be computed for the true Hyades group mem- Table I) are presented in Table III, where the bers. Two stars, HD 35991 {ΔΜυ= 4-1^46) columns are arranged as in Table II. Eggen and HD 64152 (ΔΜ^ = 2^56) are thereby (1974ib) lists 24 stars in Table III as having the thrown far from the Mv (DDO) = Mv (GROUP) most reliable proper motions; these stars are line, but the remaining stars show a similar dis- indicated by asterisks and all the (B— V), ((7- B), tribution to that shown in Figure 7a, with a mean and (V — Mv) data concerning them are taken ΔΜυ = 0^23 ± 0^47 (standard deviation, one from this reference. All other {UBV, Mv) data are star). from Eggen (1969α). The δ CN distribution of the stars in Table III V. The Wolf 630 Group of Old-Disk Stars is shown in Figure 8a, where the asterisked stars The Wolf 630 group of old-disk-population are represented by the hatched area. This dis- stars, whose space motion (V = —33 km sec-1, tribution is compared to that for the general U = —5 to —45 km sec-1) is defined by that of field in Figure 8b, where the field-star popula- the small group of stars Wolf 630 AB, Wolf 629, tion has been normalized by a factor 42/190. It and VB8 (see van Biesbroeck 1961; U.V.W = is apparent that the cyanogen anomalies of the -1 — 26, —33, -f 12 km sec and 7rtrig = 0'/155 for Wolf 630 group stars are distributed much like Wolf 630; Eggen 1969α), is among the best- that of the general field, having in fact a mean populated of stellar moving groups (Eggen 1965, δ CN = +0^007 ± 0^056 (standard deviation, 1966, 1969α). The (C—M) diagram for the group one star). The stars marked with asterisks in (Eggen 1969α, Fig. 3) bears a resemblance to Table III, however have a higher incidence of that of M 67. The group contains the variables stars with δ CN > 0. In fact, the δ CN distribu- SW And (RR Lyrae variable) and R CrB (irregu- tion of this sample is not too unlike that of M 67 lar variable) and several other stars of special giants (see Fig. 3). interest. A comparison of the group and DDO absolute

TABLE III WOLF Γ)3ϋ GROUP

CM5-48 C42-L+5 CM-1-42 S , π ^CN Mv(DDO) Mv (GROUP) Spectra 14188* lTl88 0.870 0.193 CT, 2 -0.010 +0.45 +ΐΤθ2 +0.85 +0.10 KO 111 49 28 1.210 0.918 0.246 CT , 2 +0.014 +0.49 +1.07 +0.90 +0 . 8 KO ITT 5384* 1.368 1 .321 0.313 3,4 +0.051 +0.09 +1.51 +1.92 -0.65 ñK5 S 3 9 5 * 1.160 0.828 0.096 0,4 -0.070 +1.13 4. 64 +0.96 +0.68 +2 .54 G8 IIl-ÎV 8498* 1.399 1.389 0.175 CT , 2 5.86 +1.60 +1 .95 -0 .99 Κ5 III 87 63 1.219 0.931 0.264 Β,3 +0.021 +0.35 5 .49 +1 .11 +1 .06 +1 .4 ¡2¡KI 147 28* 1.251 1.069 0.314 3.3 +0 .054 +0.80 5.88 +1.21 +1 .30 +0 . 2 8 KO 1 S65G 1.347 1.279 0.252 Β,2 -0.016 5.16 +1.47 + 1.77 +0.0 Κ5 III 17017* 1.206 0.976 0.249 3.2 +0.038 +1. 41 6,46 +1.06 +1 .10 +1.46 gK2 1 7829 1.289 1.063 0.262 CT , 2 -0.040 +0.25 5.48 +1.27 +1.31 -0.4 RK5 18322* 1.203 0.940 0.208 2.4 -0.006 +1.21 3 .90 +1.10 +1 .00 +1.25 Kl III-IV 23S08* 1.191 0.942 0.244 CT , 2 +0.050 +1. 42 6.50 +1.08 +1 .01 +2.00 KI III 23841 1.266 0.984 0.180 Β,3 -0.112 +0.07 6.68 +1 .21 +1.16 +0.55 K2 III 2 47 ΠΠ 1 .266 1.061 0.307 CT , 2 +0.028 +0.55 5.93 +1.23 +1 .35 +1 .05 K3 III 2 0 8 M 6 * 1.236 0.974 0.300 Β,3 +0.043 +0.30 4.87 +1.18 +1 .22 +0.97 K3 III 26967* 1.203 0.940 0.197 CT, 2 -0.018 +1.27 3 ,85 +1.09 +1 .03 +1.15 Κ1 III 39S23* 1 .216 0.914 0.261 CT , 2 +0.018 +0.16 4.50 +1.10 +1.00 -0.25 K; III 49878* 1.326 1 .226 0.329 Β,4 +0.050 4.53 +1.36 +1 .64 -0.52 Κ4 III 54131* 1 .189 0.866 0.193 Β,4 -0.013 +0.35 5.49 +1 .00 +0.80 +0.69 SG8 60341* 1.223 0.956 0.293 Β,3;CT , 2 +0.049 +0.50 5.64 +1.12 +1 .06 +0.89 .q;K3 S 2 8 7 0 * 1.271 0.973 0.265 Β,3 -0.035 -1.00 5.55 +1 .16 +1.12 +0.05 gK' 83618 1.300 1.110 0.265 1.5 -0.038 +0.21 3.90 +1.32 + 1 .47 -0.7 Κ3 III 85945 1.135 0.745 0.153 Β ,4 +0 .008 +0 . 43 5.96 +0.89 +0.57 +1.45 ñG5 899 62* 1.203 0.991 0.278 3.3 +0.07 6 +1.55 6.06 +1.12 +1.14 +0.81 SK3 99237 1.3 82 1.306 0.261 CT , 2 -0.020 +0.02 6.30 +1 . 50 +1.82 K5 9 42 64* 1.187 0.923 0.198 2.4 +0.007 +1. 54 3 .82 +1 .04 +0.92 KO III-IV 9 M 669 1.205 0.9 64 0.215 Β , 4 +0.003 +1. 45 6.03 +1.13 +1.08 K2 ITT 97605* 1.213 0.992 0.242 3,3 +0.023 +1. 48 5.78 +1 .12 + 1 .13 RK3 105639 1.197 0.996 0.244 3.3 +0.053 +2.06 5.94 +1.12 +1 .IM +2.15 ñK3 106760 1.227 0.969 0.229 KP, 3 -0.017 +0.86 5.01 +1 .14 +1.07 +1 .3 K' III "117 267 1.222 0.92 6 0.3 65 3.2 +0.117 -0.35 6.42 +1.11 +1 .12 +2 . SKO 120033 1.316 1 .257 0.234 Β,2 ;KP , 1 -0.023 6.04 +1 . 42 +1 .66 -0. RK5 124679 1.175 0.862 0.198 KP, 3 +0.015 +0.72 4.80 +1.05 +0 .90 +1 .25 KO III 136366 1.179 0.819 0.210 KP, 3 -0.020 -1.87 6.16 +1.02 +0.45 gG8 136514* 1.239 1 .092 0.2()3 ■1 , 3 +0.0 13 + 1. .OH S . 34 + 1. 19 + 1 .22 + 1.24 Κ 3 Τ Τ Τ 1403 0] 1.2L4 0.93 0 0 .29Μ KP ,3 +0.013 +0.57 (..31 +1.1 6 +0 . 9 6 +1 .5 s^KO 148513* 1.361 1 .257 0.3 64 2.4 +0.07 5 - 0 . 2 3 5.39 + 1.4() + 1 .79 - 0 . M f) κ4 τιτρ 148897* 1.318 0.967 0 . Η) 1 C , 3 -0 .197 -4.4: 5.23 +1 . 2 6 +1.20 +0.33 G8p 197 635* 1.229 0.955 0.289 CT , 2 +0.037 +0.29 5 .40 + 1 .12 + 1.10 +0.45 rko 203 63 8* 1 .253 0.983 0.3 50 CT , 2 +0.07 3 -0.2 6 5.46 +1.16 + 1 .12 +1.21 ñK2 20547 8 1.170 0.885 0.234 CT , 2 +0.065 +1 .1 3.75 +0.99 +0.90 +3.0 ko ur 217959* 1 .305 1 . 149 0.31 6 3.3 +0.019 +0 . 39 5.83 + 1 .34 +1 .55 +0.03 SK4 2183 56 1 .325 1 .030 0.259 C, 2 :3,1 -0.09 5 -2.53 4.78 +1.32 + 1.10 -2.2 KO I [ρ magnitudes for the stars in Table III is shown in the discussion of MacGonnell, Fiye, and Up- Figure 9, where stars with positive cyanogen gren (1972). The absolute magnitude calibration anomalies are shown as filled circles. The three of MacGonnell et al. (1972) would then indicate most discrepant points, HD 117267 (AMV = Μυ ~ H-1^0, closer to the group value. 2^8), HD 136366 (AMV = 2^3), and HD 148897 Even excluding these three most discrepant (AMV = 4™7) are labeled. Hoffleit (1964) lists stars the spread in AMV is quite large, in fact, the HD 148897 as a suspected variable of spectral mean AMV = +(^22 ± 0^69 (standard devia- type G8 Hp, while, as discussed by Eggen (1965), tion, one star). This dispersion is to be compared Roman (1952) gives the type as G8p, noting with the dispersion of ±0^46 for the true Hyades that the hydrogen and Sm lines indicate it is group members in section IV. This spread of a class II star, but the GN bands are too weak nearly 0^7 for the Wolf 630 group members is and G band too strong for class II. Indeed, the sufficiently large to make the group's reality sus- DDO indices for HD 148897, if taken at face pect. The spread in AMV for the stars with best- value, would indicate that this is a G9 II or G9 lb determined proper motions is only slightly star with δ GN = -0^20 (see the calibration of smaller (mean AMV = +0^14 ± 0^63) but is the C(45-48), C(42-45) plane, McGlure 1973). not inconsistent with a mixed group of true Wolf However, the strong Sm line may indicate that 630 group members and field stars in proportion HD 148897 is a marginal Ba n star in the sense of similar to that found for the Hyades group.

SCN

Fig. 8 —(a) 8 CN histogram for 42 Wolf 630 group stars. Hatched areas represent stars with best-determined proper motions. One star, HD 148897 lies off the diagram as indicated, (b) The same distribution as (a) but smoothed and compared to the field star distribution of Figure 1, normalized by a factor 42/190.

In Figure 10, the Wolf 630 group stars are populated 61 Cygni group (Eggen 1969α), whose plotted in the C(45-48), C(42-45) plane, reveal- existence was first suggested by Boss (1911) and ing a moderately large spread about the class Russell (1912), and the group showing the most III line. Two group stars whose DDO indices extreme old-disk-population characteristics, the appear abnormal are labeled. These stars lie in Arcturus group (Eggen 1971α, 1974α). The avail- the domain of the Ba π stars (see McClure et al. able DDO data together with UBV and group 1974) in this diagram. One, HD 148897, has al- Mv data collected from the above-mentioned ready been discussed. The second, HD 218356 references are presented in Table I Va through f, {Mv (DDO) = -2^5, δ CN = -0^10), is listed where the columns are arranged as in Table II. by Roman (1952) and Eggen (1965) as having Stars designated by Eggen (1971b) as both "prob- strong Sni. MacConnell et al. (1972) list HD able" and " possible" members of the groups are 218356 as a marginal Ba n star and Eggen (1972c) listed in Table IV, but we will consider only the discusses it as a Ban star. These two stars also probable members of the ζ Her and σ Pup lie 0^19 and 0^41, respectively, above the mean groups to be reliably assigned. Furthermore, the sequence of Hyades giants (equation (2)) in the members of the Arcturus group discussed in {U— B,B—V) plane, a further characteristic of Eggen (1974α) are those stars whose HD num- Ba π stars. bers are followed by an asterisk, and only those stars will be considered to be reliably assigned. VI. Other Old-Disk Groups Because of the very few G and Κ giants in- The other moving groups of the old-disk popu- volved in any one group and considering the lation isolated by Eggen are each more sparsely possibility of contamination by nongroup stars, populated than either the Hyades or Wolf 630 it is exceedingly difficult to draw any secure con- moving groups discussed in the preceding sec- clusions from DDO data for individual groups. tions. We examine here the G and Κ giants of the Nevertheless, we present in Figure 11 the δ CN ζ Her, elnd, σ Pup, and η Cep groups (Eggen distribution for the stars in Table IV. Group 1960, 1970b, 1971b), the somewhat more densely stars whose assignments are reliable are repre-

t T ' 1 (+0.3,-44) ¿148897

-2 o 136366

-I 117267 MJDDO)

+ 1 *

+ 2 +1 0 -I -2

Mv(GR0UP)

Fig. 9 — Comparison of DDO and group absolute magnitudes for the Wolf 630 group. Filled circles represent stars having θ CN > 0, open circles stars with 8 CN < 0 and the solid line represents Mv (GROUP) = Mv (DDO). The three most discrepant stars are labeled by their HD numbers. sented by cross hatching. It is readily apparent 2^82) lies somewhat below the mean {Mv,B~V) that all the groups, with the possible exception sequence for old-disk stars (Eggen 1971&, Fig. of the € Ind group, have a spread in δ CN larger 1) as do several other members of the ζ Her than that allowed by our experience with clusters. group. Though the DDO absolute magnitude In fact, all except the e Ind group, have a disper- may indeed be too bright, earlier, both Eggen sion in δ CN larger than that of NGC 188, which (1962, 1964) and Roman (1955) had assigned this shows the largest spread in δ CN of any cluster star a larger distance modulus. HD 72324 (υ2 studied so far (McClure 1974). Note that we are Cancri; ΔΜ^ = 1^44), a member of the 61 Cyg considering here only stars judged reliably as- group, though possessing a moderate cyanogen signed. Hence, though the € Ind group may per- anomaly (δ CN = +0^4) is noted as "strong haps satisfy the requirement of chemical homo- CN" by Eggen (1969α). Though Eggen (1969α), geniety. Figure 11 seems to indicate that a good Eggen (1962), and Roman (1955) substantially proportion of the stars in the remaining moving agree on the distance modulus of this star, Eggen groups may be incorrectly assigned. (1969α) lists the apparent visual magnitude of Figure 12 presents the comparison of Μυ HD 72324 as CTO fainter than found by either (DDO) with Μυ (GROUP) for the reliably Roman (1955) or Sanders (1966). HD 27370 assigned stars of Table IV. The three most dis- (ΔΜυ = 2^56) of the η Cep group has quite crepant points are labeled. HD 9166 (ΔΜυ = weak CN absorption (δ CN = —0^13), and the

Fig. 10 — C(45-48) vs. C(42-45) diagram for the Woli 630 group. For G and Κ stars, this diagram is equivalent to an H-R diagram. Open circles represent stars with 8 CN < 0, filled circles stars with 8 CN > 0. Two stars having anomalous C(45-48) colors are labeled by their HD numbers and are likely marginal Ba n stars.

Janes (1974a) absolute-magnitude calibration (1972) calibration, might not be reliable for such weak CN stars. Ex- [Fe/H] o = 4.5 CN - 0.2 . (3) cluding these stars, the trend in Figure 12 is for DD δ Mv (DDO) to be fainter than Mv (GROUP). In The fourth, fifth, and sixth columns contain the fact, taking the mean over all of the groups gives eccentricities, and peri- and apogalactic dis- ΔΜυ = -0^39 ± 0^67 (standard deviation, tances (in kiloparsecs) characterizing the galac- one star). tic orbits for these groups. These quantities are calculated following the model for the galactic VII. Discussion potential of Eggen, Lynden-Bell, and Sandage Table V presents a summary of the moving (1962) assuming the solar motion of Eggen groups discussed here. The second and third (1969¾). The remaining column gives the mean columns of Table V contain the mean δ CN of the ΔΜυ for the group. Only true members of the group in question and the photometrically deter- Hyades group (§ IV) have been used in obtaining mined value of [Fe/H] with respect to the sun the quantities in Table V, and only the Wolf 630 (under the assumption that iron abundance is stars with the best proper motions have been related to CN strength) calculated from Janes' employed. Furthermore, only the reliably as-

TABLE IV < OTHER OLD DTSK GROUP STARS C45-48 C^2-45 CI41-42 S ,n J CN Mv(DDO) Mv (CROUP) Spectra a) Herculis Group Members Ί1 Γ) 6 1^295 ΐΤθ35 0.411 3,2 +0^098 -lT46 6m7 6 +1T23 +1.42 +1.3 6 K3 III 43R99 1.224 0.962 0.240 CT , 2 -0.004 +0.78 5.58 +1.12 +1 .06 +1.01 gK' 90250 1 .193 0.925 0.248 Β , 3 +0.047 +1.15 6.45 +1.09 +0 .97 +1 .10 K1 III 119Ί25 1.214 0.953 0.277 (Β ,1 :KP,2 ; 2,2)+0.046 +0.77 5.35 +1 .09 +1.06 +1 .83 K! TII-IV £Herculis Group Possible Members 70523 1.202 0.908 0.167 3 ,3 -0.054 +1.06 5.77 +1.05 +0.89 +0.82 Κ ι III 71377 L . 236 1.009 0.235 CT , 2 -0.016 +1.07 5.54 +1.19 +1.14 +0.31 K2 III 129245 1.280 1 .135 0.274 Β , 3 -0.003 +0.96 6.26 +1.30 +1.46 +1.03 K3 III b) £* Indi Group Members 110409 1.190 0.941 0.199 3,3 +0.007 +1.68 4.65 +1.05 +0.96 +1.90 gK3 90170 1.140 0.808 0.090 CT , 2 -0.046 +1.70 6.26 +0.88 +0.60 +0.36 KO 142574 1.37 8 1 .355 0.254 Β , 3 5.44 +1.58 +1 .95 -0.46 K4 III 219430Λ 1,210 0.944 0.238 Β,3 +0.014 +0.92 4.22 +1.10 +1.04 +1.14 KO III c) 61 Cygni Group Members 2 31 83 1.177 0.852 0.142 C ,2 -0.047 +0.72 6.14 +1.01 +0.74 +1.85 KO III 39425 1.242 1.012 0.290 3,3 +0.032 +0.72 3.10 +1.17 +1.21 +0.75 K2 III 40460 1.184 0.877 0.172 Β , 3 -0.024 +0.85 6.59 +1.02 +0.84 +0.2 K4 III 50778 1.340 1 .246 0.222 CT , 2 -0.057 +0.84 4.07 +1. 42 +1 .68 -0.3 K4 III 55526 1.277 1.061 0.219 CT , 2 -0.071 +0.76 5.14 +1.24 +1 .30 -0.15 K4 72324 1.197 0.854 0.260 5,3 +0.038 -0.69 6.35 +1.02 +0.88 +0.75 G9 III 95272 1 .217 0.938 0.262 2,2;4,4 +0.024 +0.54 4.09 +1.10 +0.99 +0.8 KO III 106365 1.209 0.958 0.227 Β , 5 +0.007 +1.20 6.84 +1.15 +1.06 +0.45 K2 III 131111 1.186 0.899 0.138 Β,3 -0.057 +1.48 5.48 +1.02 +0.84 +1 .25 KO III-IV 137704 1.323 r.201 0.218 Β,3 -0.071 +1.00 5.46 +1. 40 +1.64 -0.45 K4 III 210005 1 .210 0.9 61 0.296 2,3 +0.074 +0.85 6.30 +1.12 +1.05 +0.45 KO 219Μ0Ί 1.198 0 . r]2 8 0.192 CT ,2 -0.017 +1.34 6.52 +1.08 +0.9 Κ ι III d) tf-Tuppis Group Members 3457 1.301 1.171 0.228 3.3 -0.057 +1.06 6.40 +1.35 +1 .50 -0.23 Κ4 III 37160 1.157 0.831 0.077 1.4 -0.082 +1.38 4.08 +0.95 +0.65 +0.86 G8 I Up 37763 1.216 1.020 0.255 3,3 +0.037 +1.61 5.18 +1.13 +1 .18 +0.86 K4 III 40801 1.166 0.866 0.135 C , 3 -0.031 +1.44 6.08 +0.98 +0.78 +0.91 KO III 59717 1.344 1.318 0.257 3,3 +0.009 3.24 +1.52 +1.78 -0.66 K5 III 77729 1.331 1.174 0.217 C,1 -0.091 +0.06 7.65 +1.40 +1.58 -0.05 Κ4 III 100470 1.198 0.893 0.187 C , 6 -0.030 +0.80 6.38 +1.06 +0.91 +0.16 KO III 107328 1.249 0.982 0.199 1.5 -0.073 +0.63 4.95 +1.15 +1.15 +0 .41 KO III 130694 1.319 1.139 0.219 C , 2 -0.094 +0.58 4.41 +1.40 +1.48 -0.55 gKM (TPuppis Group Possible Member 1.230 0.975 0.266 C,3 +0.017 +0.67 7.44 +1.14 +1.21 Cephei Group Members 27370 1.223 0.859 0.131 C , 2 -0.131 -1.67 7.14 +1.16 +0.79 +0.89 gG5 43380 1.207 0.993 0.254 3,3 +0.046 + 1.60 6.40 +1.10 +1.12 +0.30 K2 III 62044 1.220 0.938 0.234 C, 2 -0.009 +0.61 4.29 +1.12 +0.97 -0.16 Kip 72184 1.208 0.961 0.310 3,3 +0.092 +0.84 5.90 +1.10 +1.15 +0.40 K2 III 121146 1.245 1.053 0.243 Β ,4 -0.013 +1.13 6.28 +1.00 +1.08 s gK2 125932 1.278 1.174 0.305 C, 2 +0.043 +0.7 4.78 +1.33 +1.55 +0.03 K5 III 126271 1.249 1.031 0.284 3,3 +0.019 +0.72 6.20 +1.18 +1.24 +0 . 30 gK4 129336 1.172 0.806 0.169 (B,2;KP,1) -0.024 -0.14 5.55 +0.95 +0.65 +0.64 G8 III f) Arcturus Group Members 6497* 1.230 1.035 0.263 3,3 +0.026 +1.22 6.42 +1.19 +1.22 +1.00 K2 III 12369* 1.358 1.205 0.188 CT,2 -0.126 +0.34 7.06 +1.44 +1.63 -0.57 K4 III 124897* 1.285 1.026 0.200 ** -0.105 -0.15 -0.05 +1.23 +1.28 -0.25 K2 III 175545 1.226 1.054 0.221 Β,5 -0.006 +1.77 7.45 +1.22 -0.20 K2 III 176704 1.282 1.042 0.386 Β,2 +0.088 -0.48 5.64 +1.23 +1.26 -0.24 K3 III 191046* 1.246 0.934 0.168 6,3 -0.110 -0.25 7.06 +1.15 +1.02 +0.87 G9 III 196866* 1.278 1.042 0.214 Β,2 -0.081 +0.49 6.98 +1.30 +1.34 +0.21 K2 III 213893* 1.362 1.320 0.199 Β,3 -0.060 +0.76 6.69 +1.54 +1 .83 -0.57 Κ5 III Arcturus Group Possible Members 19735 1.319 1.245 0.243 C ,2 -0.022 +0.7 6.35 + 1 .44 +1.67 -0.39 K5 III m9161 1.357 1.307 0.242 C ,2 -0.020 +0.56 4.84 +1.50 +1 .83 -1.06 K5 III 175305 1.103 0.645 -0.002 1,4 7.16 +0.76 +0.16 +2 .82 G5 III 191584 1.264 1.055 0.339 CT, 2 +0.061 +0.3 6 6.20 +1 .22 +1 .29 -0. 60 K2 ITT Weighted mean of McClure and van den Bergh (1968) and unpublished observations by McClure.

Her 3-- ζ

2 I I I I I I I Π ' 1 Γ I I I PfΚ I I I € I nd 3-

I ι ι I ι ι ι ι pi ι ι ι ^ ι ι I ι ι ι ι I ι ι ι 61 Cyg 3--

/Λ 1¾ Pj7] I I I I 4 I I I I I I Pup 3-- σ

-H- ■H- I I I I I I I rjCep 3--

^ ι ι I ι ι ι ι I ι η I I I Π I I i

3-- Arcturus

m η ι J—L ■ FZ^ ■ i i 11 11 J_-L -0.10 -0.05 0.0 +0.05 +0.10

SCN

Fig. 11 — 8 CN distributions for the other old-disk groups studied here. Stars represented by hatched areas are those whose status as members is most reliable as judged from Egg en's work.

signed members of the other old-disk groups and show the well-known correlation of metal- (§ VI) have been used. All stars mentioned in the licity with eccentricity (Eggen, Lynden-Bell, preceding sections as having unusually large and Sandage 1962), the one exception being the values of ΔΜυ have also been excluded. Note τ] Cep moving group. There is also a general that even if none of the old-disk groups are in trend in ΔΜυ in the sense that for groups with fact real, the space motions of the stars compris- e > 0.2, the DDO absolute magnitudes are sys- ing them are in all probability approximately tematically fainter than those obtained by assum- correct, and hence it would still be worthwhile ing membership in a moving group (see Fig. 13 to look at the correlations between mean photo- where error bars represent the standard error of metric and kinematic properties. The moving the mean for each group). We believe that it is groups in Table V are arranged according to the highly unlikely that this effect can be due to a eccentricities of their respective galactic orbits. metallicity dependence of the Mv (DDO) cali-

Mv(DDO)

+ 1.0 0.0 -1.0

MyiGROUP)

Fig. 12 — Comparison of Mv (DDO) and Mv (GROUP) for the stars represented as hatched areas in Figure 11. The three most discrepant stars are labeled by their HD numbers. bration since Janes (1972) used a very large old-disk groups. sample of stars of a wide range of metal abun- One possible, but rather speculative explana- dance in his calibration, and determined a well- tion is that errors in the spectroscopic or photo- defined correction factor for metallicity. This metric magnitude calibration used to initially correction would have to be entirely removed in select group members are reflected in the final order to eliminate the correlation of ΔΜ^ with mean group absolute magnitude. For example, eccentricity shown in Figure 13. This seems un- if MK classification were used to obtain an warranted on the basis of Janes' calibration. In absolute magnitude, and hence a velocity, too addition the known behavior of the DDO bright a magnitude may be assigned to very old indices with blanketing (see Osborn 1973) indi- giants of the age of NGC 188. The opposite cates that the magnitude calibration should have would be the case for young giants of Hyades age. a metallicity dependence on the order of that This is expected since giant stars of NGC 188- determined empirically by Janes. Furthermore, type population are fainter than those of Hyades- the relation between δ CN and ΔΜυ for the type population whereas the Μ Κ calibration data in Table V is not clear-cut. For example, gives only one value for absolute magnitude of the r) Cep group lies above the mean δ CN, a class III star of a given spectral type. Hence eccentricity relation formed by the other groups, stars that are intrinsically fainter, and therefore whereas it possesses negative ΔΜ^ as do other nearer, may be mistakenly included in a group

TABLE V

SUMMARY OF PHOTOMETRIC AND KINEMATIC PROPERTIES

Group [Fe/Hj R . R ΔΜ. S CN DDO mn η max

Hyades +0^063 +0.1 0.08 9.2 10.9 +0723

Wolf 630 +0.024 -0.1 0.15 8.0 10.8 +0.14

Her. +0.030 -0.1 0.18 7.2 10.4 +0.41

CInd . -0.008 -0.2 0.21 7.3 11.25 -0.30

61 Cyg. -0.019 -0.3 0.26 6 .5 11.2 -0.41

(TPup . -0.046 -0.4 0.36 4.9 10.5 -0.72

"^Cep. +0.022 -0.1 0.37 4.6 10.05 -0.43

Arcturus -0.076 -0.5 0.47 3.8 10.5 -0.29

and their assigned group absolute magnitude Though we have not been able to confirm the will be brighter than reality. Because the rela- reliability of group assignments for any of the old- tion between absolute magnitude and the result- disk groups studied, it is still likely that they ing velocity in the {U,V) plane is nonlinear, represent reliable samples of the old-disk popu- fewer stars with an error in absolute magnitude lation. As mentioned above, the luminosities and toward the brighter direction will be incorrectly space motions for these stars derived on the included in the groups. assumption of group memberships are also The confirmation of the assignment of at least likely to be approximately correct. 50% of the red-giant members of the young-disk- Finally, note that the present results imply population Hyades moving group (not counting that the use of group membership alone to dis- the cluster members) may well indicate that cuss the properties of peculiar stars is an unre- many of the stars of other young-disk groups, liable procedure. This is because there may be upon whom the disruptive forces of differential up to a 50% chance that the particular star dis- galactic rotation and stellar encounters have cussed is in fact a spurious member. This is not had but a short time to work, may be reliably surprising since Eggen s lists of group stars were assigned. Care must be taken, however, to in- selected on the basis of space motions alone sure that the requirement of chemical homo- without the benefit of a metallicity indicator geniety is satisfied before group assignments for such as δ CN. individual stars can be considered secure. Fur- Throughout, we have assumed that chemical thermore, as 50% of the original list of Hyades homogeniety of the degree found in clusters is group stars may be spurious members, perhaps a requisite for a genuine moving group, and we as many as 50% of the listed members of the old- feel that we have successfully used this criterion disk groups may also be incorrectly assigned. to segregate out spurious group members in the The spread in δ CN found here for the old-disk case of the Hyades moving group. It may be that groups studied would be compatible with this, moving group stars are not bound by such a re- as would the trend in ΔΜυ discussed above. quirement, perhaps because the formation of

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