2007A&A...468..663T

It is known that the surface lithium abundances of field solar-analog G dwarfs show a large dispersion of >2dex (among which our Sun is located at the lower end) despite the similarity of stellar parameters, and planet-host stars tend to show comparatively lower Li abundances in the narrow T_eff range. To investigate the reason for these phenomena, an extensive study of Li abundances and their dependence on stellar parameters was carried out for a homogeneous sample of 118 selected solar analogs based on high-dispersion spectra obtained at Okayama Astrophysical Observatory. The atmospheric parameters were spectroscopically determined by using the equivalent widths of Fe I and Fe II lines, the ages/masses were estimated from stellar evolutionary tracks, and the width of the macrobroadening (rotation plus macroturbulence) function as well as Li abundances (A_Li) were established by spectrum-fitting analyses. The resulting A_Li vs. T_eff relation revealed a characteristic inverse-triangle-like distribution enclosed by two clear-cut boundaries (the slanted one running from ∼5900K to ∼5800K and the vertical one at ∼5700K), while the Sun is located around its lowest apex. More significantly, A_Li in this region of large dispersion was found to closely correlate with the macrobroadening width (v_r+m), which is considered to be the most important parameter. With a reasonable assumption that the difference of rotational velocity is mainly responsible for the variety of v_r+m, we may conclude that the stellar angular momentum plays the decisive role in determining the surface Li abundances of solar-analog stars in the T_eff range of ∼5900-5700K. The low-Li tendency of planet-host stars may thus be interpreted in terms of rotational characteristics.