Lithium and Rapid Rotation in Chromospherically Active Single Giants

The rotational velocities presently obtained via spectroscopic observations of a group of moderately rapidly rotating, chomospherically active single giants indicate that Gray\u27s (1989) rotostat hypothesis requires modification. Their rapid rotation appears to be due to high Li abundances, and results in increased chromospheric activity. A scenario is projected in which the surface convection zone reaches the rapidly rotating core just as a star begins its first ascent of the giant branch, and dredges both high angular momentum material and freshly synthesized Li to the surface

Infrared Echelle Spectroscopy of Palomar6 and M71

We present high-resolution infrared echelle spectroscopy for the globular clusters Palomar 6 and M71. Our mean heliocentric radial velocity of Palomar 6 is +180.6 +/- 3.2 km sec/s and is 20 km/s lower than that found by Minniti in 1995. Contrary to the previous metallicity estimates using low-resolution spectroscopy, our results show that Palomar~6 has an intermediate metallicity with [Fe/H] = -1.0 +/- 0.1 and is slightly more metal-poor than M71. Reasonable changes in the surface temperature or the microturbulent velocity of the model atmospheres do not affect [Fe/H] at more than +/- 0.2 dex. In spite of its high metallicity, based on the spectrum of a single cluster member the [Si/Fe] and [Ti/Fe] ratios of Palomar~6 appear to be enhanced by 0.4 dex and 0.5 dex, respectively, suggesting that the Galactic inner halo may have experienced a very rapid chemical enrichment history.Comment: Accepted for publication in AJ (Nov. 2004

Stellar Iron Abundances at the Galactic Center

We present measurements of [Fe/H] for six M supergiant stars and three giant stars within 0.5 pc of the Galactic Center (GC) and one M supergiant star within 30 pc of the GC. The results are based on high-resolution (lambda / Delta lambda =40,000) K-band spectra, taken with CSHELL at the NASA Infrared Telescope Facility.We determine the iron abundance by detailed abundance analysis,performed with the spectral synthesis program MOOG.The mean [Fe/H] of the GC stars is determined to be near solar,[Fe/H] = +0.12 $\pm$ 0.22. Our analysis is a differential analysis, as we have observed and applied the same analysis technique to eleven cool, luminous stars in the solar neighborhood with similar temperatures and luminosities as the GC stars. The mean [Fe/H] of the solar neighborhood comparison stars, [Fe/H] = +0.03 $\pm$ 0.16, is similar to that of the GC stars. The width of the GC [Fe/H] distribution is found to be narrower than the width of the [Fe/H] distribution of Baade's Window in the bulge but consistent with the width of the [Fe/H] distribution of giant and supergiant stars in the solar neighborhood.Comment: 41 pages, 9 figures, ApJ, in pres

Lithium Abundances in the alpha Per Cluster

Lithium abundances are presented and discussed for 70 members of the 50 Myr old open cluster alpha Per. More than half of the abundances are from new high-resolution spectra. The Li abundance in the F-type stars is equal to its presumed initial abundance confirming previous suggestions that pre-main sequence depletion is ineffective for these stars. Intrinsic star-to-star scatter in Li abundance among these stars is comparable to the measurement uncertainties. There is marginal evidence that the stars of high projected rotational velocity v sini follow a different abundance vs temperature trend to the slow rotators. For stars cooler than about 5500 K, the Li abundance declines steeply with decreasing temperature and there develops a star-to-star scatter in the Li abundance. This scatter is shown to resemble the well documented scatter seen in the 70 Myr old Pleiades cluster. The scatter appears to be far less pronounced in the 30 Myr clusters which have been studied for Li abundance.Comment: Accepted for publication in MNRAS 30 Pages, 4 Figures, 5 Table

Two K Giants with Supermeteoritic Lithium Abundances: HDE 233517 and HD 9746

Two unusual Li-rich K giants, HDE 233517 and HD 9746, have been studied. Optical spectroscopy and photometry have been obtained to determine the fundamental parameters of HDE 233517, a single K2 III with an extremely large infrared excess. The spectra yield Teff=4475 K, logg=2.25, [Fe/H]=-0.37, vsini=17.6 km s-1, and a non-LTE logɛ(7Li)=4.22. Photometric observations reveal low-amplitude light variability with a period of 47.9 days. Combined with other parameters, this results in a minimum radius of 16.7 Rsolar and minimum distance of 617 pc. Comparison of spectra obtained in 1994 and 1996 show profile variations in Hα and the Na D lines indicative of changing mass loss. Optical spectra of HD 9746, a chromospherically active giant, were analyzed. The Teff=4400 K and revised Hipparcos-based gravity of logg=2.30 lead to a non-LTE logɛ(7Li)=3.75. The Li abundances in both stars are supermeteoritic. By the inclusion and exclusion of 6Li in the syntheses, we show that consistent 7Li abundances are obtained only when 6Li is absent in the synthetic fit. This provides evidence for fresh 7Li production and excludes both preservation of primordial Li and planetary accretion as viable scenarios for the formation of Li-rich giants. Both stars lie in close proximity to the red giant luminosity bump supporting the hypothesis that 7Li production is caused by the same mixing mechanism that later results in CN processing and lowers the 12C/13C ratio to nonstandard values