{
  "id": "2203.04528",
  "version": "v1",
  "published": "2022-03-09T05:25:48.000Z",
  "updated": "2022-03-09T05:25:48.000Z",
  "title": "Merger and post-merger of binary neutron stars with a quark-hadron crossover equation of state",
  "authors": [
    "Yong-Jia Huang",
    "Luca Baiotti",
    "Toru Kojo",
    "Kentaro Takami",
    "Hajime Sotani",
    "Hajime Togashi",
    "Tetsuo Hatsuda",
    "Shigehiro Nagataki",
    "Yi-Zhong Fan"
  ],
  "comment": "6+6 pages, 5+4 figures",
  "categories": [
    "astro-ph.HE",
    "gr-qc",
    "nucl-th"
  ],
  "abstract": "Fully general-relativistic binary-neutron-star (BNS) merger simulations with quark-hadron crossover (QHC) equations of state (EOSs) are studied for the first time. In contrast to EOSs with purely hadronic matter or with a first-order quark-hadron transition, in the transition region QHC EOSs show a peak in sound speed, and thus a stiffening. We study the effects of such stiffening in the merger and post-merger gravitational (GW) signals. Through simulations in the binary-mass range $2.5 < M/M_{\\odot} < 2.75$, characteristic differences due to different EOSs appear in the frequency of the main peak of the post-merger GW spectrum ($f_2$), extracted through Bayesian inference. In particular, we found that (i) for lower-mass binaries, since the maximum baryon number density ($n_{\\rm max}$) after the merger stays below $3-4$ times the nuclear-matter density ($n_0$), the characteristic stiffening of the QHC models in that density range results in a lower $f_2$ than that computed for the underlying hadronic EOS and thus also than that for EOSs with a first-order phase transition, and (ii) for higher-mass binaries, where $n_{\\rm max}$ may exceed $4-5 n_0$ depending on the EOS model, whether $f_2$ in QHC models is higher or lower than that in the underlying hadronic model depends on the height of the sound-speed peak. Comparing the values of $f_2$ for different EOSs and BNS masses gives important clues on how to discriminate different types of quark dynamics in the high-density end of EOSs and is relevant to future kHz GW observations with third-generation GW detectors.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2022-03-09T05:25:48.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "binary neutron stars",
      "quark-hadron crossover equation",
      "qhc models",
      "maximum baryon number density",
      "transition region qhc eoss"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 6,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}