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7 Velocity data


 

 
Table 8: Velocity data and age determinations. The top half of the table contains the stars in this study and the lower section stars from Gonzalez (1999) and Gonzalez & Laws (2000). Age estimates, using isochrones, from this study are given in Col. 6 top half. The age estimates for the stars in the second section are also based on the Bertelli et al. (1994) stellar isochrones, with typical uncertainties of 1 to 2 Gyrs. In Col. 7 we reproduce the Ca II activity index ages from Gonzalez (1998). In the last column we give [Fe/H] as determined in this study or from Gonzalez (1999) and Gonzalez & Laws (2000)
ID Name $U_{\rm LSR}$ $V_{\rm LSR}$ $W_{\rm LSR}$ Age (isochrones) Age (Ca II) [Fe/H]
    (kms-1) (kms-1) (kms-1) (Gyr) (Gyr) 
HD 10780   -14.8 -11.3 1.6 -   -0.02
HD 32147   10.7 -51.8 -6.3 -   0.28
HD 99491   -49.8 -4.1 -8.7 12.6-15.8   0.22
HD 104304   31.6 -10.2 -9.2 $\leq$15.8   0.15
HD 121370   19.2 -12.0 4.6 2.5-3.2   0.24
HD 145675 14 Her 35.6 -2.0 -2.9 10-13.0   0.47
HD 182572   -106.7 -25.2 -13.5 7.9-10.0   0.34
HD 196755   -48.1 29. -11.7 2.5-3.2   0.02
HD 9826 $\upsilon$ And 4.3 -34.1 0.6 2.7   0.12
HD 75732 $\rho^{1}$ Cnc -27.3 -13.2 -0.9   5 0.45
HD 75289   31.1 -12.4 -14.5 2.1   0.28
HD 95128 47 UMa -14.7 2.6 8.8 6.3 7 0.01
HD 117176 70 Vir 23.2 -46.9 3.4 8 9 -0.03
HD 120136 $\tau$ Boo -23.5 -13.8 0.3 1   0.32
HD 143761 $\rho$ CrB 64.1 -30.7 28.5 12.3   -0.29
HD 186408 16 Cyg A 27.6 -23.6 7.2 9.0   0.11
HD 186427 16 Cyg B 27.1 -24.7 5.4 9.0 7 0.06
HD 187123   11.6 -10.6 -36.4 5.5   0.16
HD 217014 51 Peg -5.6 -24.2 22.3 6.0 10 0.21
HD 210277   12.4 -46.8 3.0 8.5   0.24


Spatial velocity data were calculated using the Hipparcos parallaxes and proper motions. Radial velocities were taken from Barbier-Brossat et al. (1994). For our stars the uncertainties in the parallaxes are small, less than 3% of the parallax, Table 1. Data were also obtained for the stars from the Gonzalez (1999) compilation. The velocities are presented in Table 8. Note that we here quote the velocities relative to the local standard of rest (LSR) and Gonzalez (1999) quoted velocities relative to the sun.

From Table 8 we see that all the stars have W-velocities well below the $\sigma_W$ of the general population of stars with similar B-V. Figure 5 in Dehnen & Binney (1998) illustrates how $\sigma_{U,V,W}$ varies with B-V. Also, most of the stars in Table 8 have both V and U-velocities well below 1 $\sigma $ for the general population. We have quantified this by calculating the probabilities that any one of our stars belongs to either the thin or the thick disk by using a model where 94% of the solar neighbourhood stars belong to a thin disk with $\sigma_U=35$, $\sigma_V=25$, and $\sigma_W=17$ kms-1 and the remaining 6% to the thick disk with $\sigma_U=70$, $\sigma_V=50$, and $\sigma_W=34$ kms-1. Only one of our stars, HD 182572, has a probability that it belongs to the thick disk larger than that it should belong to the thin. We estimate that, given the galactic model, this star has 75% chance of belonging to the thick disk. Thus, we conclude that our SMR and planet-bearing stars samples the thin disk.

Fuhrmann (1998) found that stars with thick disk kinematics were enhanced in [Mg/Fe] as compared to thin disk stars at the same metallicity. We have not measured Mg lines in our spectra. We did, however, measure Si, and our abundance result for HD 182572 gives [Si/Fe]  $= 0.16 \pm 0.09$. Compared with the general trend of [Si/Fe] for metal-rich stars in Feltzing & Gustafsson (1998), this is above the mean; however, their data exhibit a large scatter. We have also determined Ca abundances for this star, however, only one line was available. This line seems to give fairly low Ca abundances in all of the stars with more than two lines observed and may thus be underestimating the true Ca abundance in this star. Note that it is not inconsistent that we also find thin disk stars with the same Si abundance as, if HD 182572 is a thick disk star, then it might be showing us the abundance trend after the decline in [X/Fe], where X is either O or an $\alpha $-element, sets in due to increasing relative contribution of SNIa.


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