{
  "abstract": "Novae are spectroscopically classified as Fe II or He/N according to the dominance of Fe II, or He and N emission lines in their pre-nebular spectra, while spectra exhibiting both are classified as hybrid. Evidence suggests that these spectral classes represent spectral evolution. We investigate this scenario using a large spectroscopic dataset and introduce a quantitative coefficient, $κ$, to characterise the relative strength of Fe II and He/N emission. The coefficient is defined as the ratio of the flux of the Fe II ($\\lambda5169$) line to the mean flux of five He and N emission lines, with $κ>1$ indicating Fe II-dominated spectra and $κ<1$ indicating He/N-dominated spectra. We apply this method to 26 novae using spectra from the Astronomical Ring for Amateur Spectroscopy (ARAS) Database and compare the evolution of $κ$ with optical light curves. Fifteen of the 24 classical novae and one of the two recurrent novae exhibit at least one transition between Fe II- and He/N-dominated phases, while temporal trends suggest this fraction could approach 90% with complete spectroscopic coverage. The $κ$ coefficient closely tracks the optical light curves and repeatedly crosses unity in novae exhibiting jitters, revealing non-monotonic spectral evolution linked to brightness fluctuations. These results support the interpretation of Fe II, He/N, and hybrid spectra as evolutionary stages rather than distinct nova types and establish $κ$ as a quantitative tool for tracing nova spectral evolution while reducing biases from incomplete spectroscopic coverage.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.22432",
  "author_total": 3,
  "authors": [
    {
      "name": "Maria Kopsacheili"
    },
    {
      "name": "Martín Guerrero"
    },
    {
      "name": "Diego Alejandro Vasquez Torres"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7s747nxwz9kbd.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.22432",
  "fulltext_url": null,
  "id": "7s747nxwz9kbd",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.22432",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ],
    [
      "openalex",
      "3103|Stellar, planetary, and galactic studies"
    ]
  ],
  "openalex": "W7214056612",
  "pdf_url": "https://arxiv.org/pdf/2609.22432",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-18",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7s747nxwz9kbd.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:23:19Z",
      "native_id": "2609.22432",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.22432"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "A Quantitative Method to Investigate the Spectral Class Time Evolution of Novae",
  "title_text": "A Quantitative Method to Investigate the Spectral Class Time Evolution of Novae",
  "type": "preprint",
  "updated_at": "2026-11-09T00:20:35Z",
  "url": "https://research.draconitic.com/paper/7s747nxwz9kbd",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.3847/1538-4357/aeb0a0",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}