2. Selection of stars
The program stars were selected from the large survey of nearby disk dwarfs by Edvardsson et al. (1993), which includes accurate values of atmospheric parameters, abundances, kinematics and ages of 189 main sequence stars distributed in metallicity from to +0.3. As we wanted to avoid stars formed from interstellar gas greatly enriched in 7Li from AGB stars or novae, the first condition for including a star was . Next, only stars with 5900 K were included in order to maximize the chance of survival of some 6Li. Finally, the program had to be limited to a few of the brightest stars in order to be able to reach the high S/N that is needed to determine the lithium isotope ratio from the profile of the 6707.8 Å LiI line.
The five stars observed are listed in Table 1. The effective temperature (derived from the color index), the logarithmic surface gravity, the iron abundance, and the microturbulence velocity, are taken from Edvardsson et al. (1993). Note, that none of the stars are significantly affected by interstellar reddening according to the color excesses derived from the index and . According to the kinematical parameters of the stars as given in Edvardsson et al. (1993) they belong to either the thick disk or the old thin disk. The -elements, e.g. O and Mg, are somewhat enhanced in the stars, ranging from [/Fe] in HR 8181, HD 68284 and HD 130551 to [/Fe] in HR 2883 and HR 3578.
Table 1. List of program stars including the visual magnitude and atmospheric parameters adopted from Edvardsson et al. (1993)
© European Southern Observatory (ESO) 1999
Online publication: July 16, 1999