WIYN Open Cluster Study LXXXV. Li in NGC 2243 -- Implications for
  Stellar and Galactic Evolution
  High-dispersion spectra in the Li 6708 Angstrom region have been obtained and
analyzed in the old, metal-deficient cluster, NGC 2243. From Hydra spectra for
29 astrometric and radial-velocity members, we derive rotational velocities, as
well as [Fe/H], [Ca/H], [Si/H], and [Ni/H] based on 17, 1, 1, and 3 lines,
respectively. Using ROBOSPECT, an automatic equivalent width measurement
program, we derive [Fe/H] = -0.54 +/- 0.11 (MAD), for an internal precision for
the cluster [Fe/H] below 0.03 dex. Given the more restricted line set,
comparable values for [Ca/H], [Si/H], and [Ni/H] are -0.48 +/- 0.19, -0.44 +/-
0.11, and -0.61 +/- 0.06, respectively. With E(B-V) = 0.055, appropriate
isochrones imply (m-M) = 13.2 +/- 0.1 and an age of 3.6 +/- 0.2 Gyr. Using
available VLT spectra and published Li abundances, we construct a Li sample of
over 100 stars extending from the tip of the giant branch to 0.5 mag below the
Li-dip. The Li-dip is well populated and, when combined with results for NGC
6819 and Hyades/Praesepe, implies a mass/metallicity slope of 0.4
solar-mass/dex for the high mass edge of the Li-dip. The A(Li) distribution
among giants reflects the degree of Li variation among the turnoff stars above
the Li-dip, itself a function of stellar mass and metallicity and strongly
anticorrelated with a v_rot distribution that dramatically narrows with age.
Potential implications of these patterns for the interpretation of Li among
dwarf and giant field populations, especially selection biases tied to age and
metallicity, are discussed.
