{
  "id": "2302.07886",
  "version": "v1",
  "published": "2023-02-15T19:00:01.000Z",
  "updated": "2023-02-15T19:00:01.000Z",
  "title": "Observational Signatures of Carbon-Oxygen White Dwarf Merger Remnants",
  "authors": [
    "Philippe Z. Yao",
    "Eliot Quataert",
    "Andy Goulding"
  ],
  "comment": "12 pages, 8 figures, 2 tables, submitted to MNRAS",
  "categories": [
    "astro-ph.SR",
    "astro-ph.GA"
  ],
  "abstract": "Many double white dwarf (WD) mergers likely do not lead to a prompt thermonuclear explosion. We investigate the prospects for observationally detecting the surviving remnants of such mergers, focusing on the case of mergers of Carbon-Oxygen WDs. For $\\sim 10^4$ yr, the merger remnant is observationally similar to an extreme AGB star evolving to become a massive WD. Identifying merger remnants is thus easiest in galaxies with high stellar masses (high WD merger rate) and low star formation rates (low birth rate of $\\sim 6-10 \\,{\\rm M_{\\odot}}$ stars). Photometrically identifying merger remnants is challenging even in these cases because the merger remnants appear similar to He stars and post-outburst classical novae. We propose that the most promising technique for discovering WD merger remnants is through their unusual surrounding photoionized nebulae. We use CLOUDY photoionization calculations to investigate their unique spectral features. Merger remnants should produce weak hydrogen lines and strong carbon and oxygen recombination and fine-structure lines in the UV, optical and IR. With integral field spectrographs, we predict that hundreds of candidates are detectable in M87 and other nearby massive galaxies. Dust somewhat reduces the optical line emission for nebula radii $\\lesssim 10^{17}$ cm, but the sources spend most of their time with larger radii when dust is less important. Our models roughly reproduce the WISE nebula surrounding the Galactic WD merger candidate IRAS 00500+6713; we predict detectable [Ne VI] and [Mg VII] lines with JWST but that the mid-IR WISE emission is dominated by dust not fine-structure lines.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2023-02-15T19:00:01.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "carbon-oxygen white dwarf merger remnants",
      "observational signatures",
      "identifying merger remnants",
      "galactic wd merger candidate iras",
      "low star formation rates"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 12,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}