HIGH PRECISION ABUNDANCES OF THE OLD SOLAR TWIN HIP 102152: INSIGHTS ON Li DEPLETION FROM THE OLDEST SUN

Abstract

We present the first detailed chemical abundance analysis of the old 8.2 Gyr\nsolar twin, HIP 102152. We derive differential abundances of 21 elements\nrelative to the Sun with precisions as high as 0.004 dex ($\\lesssim$1%), using\nultra high-resolution (R = 110,000), high S/N UVES spectra obtained on the\n8.2-m Very Large Telescope. Our determined metallicity of HIP 102152 is [Fe/H]\n= -0.013 $\\pm$ 0.004. The atmospheric parameters of the star were determined to\nbe 54 K cooler than the Sun, 0.09 dex lower in surface gravity, and a\nmicroturbulence identical to our derived solar value. Elemental abundance\nratios examined vs. dust condensation temperature reveal a solar abundance\npattern for this star, in contrast to most solar twins. The abundance pattern\nof HIP 02152 appears to be the most similar to solar of any known solar twin.\nAbundances of the younger, 2.9 Gyr solar twin, 18 Sco, were also determined\nfrom UVES spectra to serve as a comparison for HIP 102152. The solar chemical\npattern of HIP 102152 makes it a potential candidate to host terrestrial\nplanets, which is reinforced by the lack of giant planets in its terrestrial\nplanet region. The following non-local thermodynamic equilibrium Li abundances\nwere obtained for HIP 102152, 18 Sco, and the Sun: log $\\epsilon$ (Li) = 0.48\n$\\pm$ 0.07, 1.62 $\\pm$ 0.02, and 1.07 $\\pm$ 0.02, respectively. The Li\nabundance of HIP 102152 is the lowest reported to date for a solar twin, and\nallows us to consider an emerging, tightly constrained Li-age trend for solar\ntwin stars.\n