{
  "id": "2307.04086",
  "version": "v1",
  "published": "2023-07-09T02:42:21.000Z",
  "updated": "2023-07-09T02:42:21.000Z",
  "title": "Age of FGK Dwarfs Observed with LAMOST and GALAH: Considering the Oxygen Enhancement",
  "authors": [
    "Tiancheng Sun",
    "Zhishuai Ge",
    "Xunzhou Chen",
    "Shaolan Bi",
    "Tanda Li",
    "Xianfei Zhang",
    "Yaguang Li",
    "Yaqian Wu",
    "Sarah A. Bird",
    "Ferguson J. W.",
    "Jianzhao Zhou",
    "Lifei Ye",
    "Liu Long",
    "Jinghua Zhang"
  ],
  "comment": "18 pages, 12 figures, accepted for publication in ApJS",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "Varying oxygen abundance could impact the modeling-inferred ages. This work aims to estimate the ages of dwarfs considering observed oxygen abundance. To characterize 67,503 LAMOST and 4,006 GALAH FGK-type dwarf stars, we construct a grid of stellar models which take into account oxygen abundance as an independent model input. Compared with ages determined with commonly-used $\\alpha$-enhanced models, we find a difference of $\\sim$9% on average when the observed oxygen abundance is considered. The age differences between the two types of models are correlated to [Fe/H] and [O/$\\alpha$], and they are relatively significant on stars with [Fe/H] $\\lesssim$ -0.6 dex. Generally, varying 0.2 dex in [O/$\\alpha$] will alter the age estimates of metal-rich (-0.2 $<$ [Fe/H] $<$ 0.2) stars by $\\sim$10%, and relatively metal-poor (-1 $<$ [Fe/H] $<$ -0.2) stars by $\\sim$15%. Of the low-O stars with [Fe/H] $<$ 0.1 dex and [O/$\\alpha$] $\\sim$ -0.2 dex, many have fractional age differences of $\\geq$ 10%, and even reach up to 27%. The fractional age difference of high-O stars with [O/$\\alpha$] $\\sim$ 0.4 dex reaches up to -33% to -42% at [Fe/H] $\\lesssim$ -0.6 dex. We also analyze the chemical properties of these stars. We find a decreasing trend of [Fe/H] with age from 7.5-9 Gyr to 5-6.5 Gyr for the stars from the LAMOST and GALAH. The [O/Fe] of these stars increases with decreasing age from 7.5-9 Gyr to 3-4 Gyr, indicating that the younger population is more O-rich.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-07-09T02:42:21.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "fgk dwarfs",
      "oxygen enhancement",
      "fractional age difference",
      "galah fgk-type dwarf stars",
      "independent model input"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 18,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}