{
  "abstract": "Methyl cyanide is one of the most abundant nitrogen-bearing complex organic molecules observed in the gas phase around low- and high-mass protostars. However, very few observations exist with a broad enough frequency coverage and sufficiently high sensitivity to systematically characterize its minor isotopologues toward such regions. We add to this number by analyzing data toward BHR71-IRS1 taken as part of the Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) Large Program over a ~33 GHz frequency range. We studied as many isotopologues of methyl cyanide as possible toward BHR71-IRS1. We found the column densities and excitation temperatures via spectral fitting and assuming local thermodynamic equilibrium. We then compared the derived column density ratios with those toward IRAS 16293-2422 A and B, V883 Ori, G31.41+0.31, and Sgr B2(N2b). We detect CH3CN, CH3CN $v_8$=1, 13-CH3CN, CH3-13-CN, CH3C-15-N, CH2DCN, and CHD2CN. The column density ratio of 13-CH3CN/CH3-13-CN is around unity, in agreement with previous observations. The CH2DCN/CH3CN ratios are similar for all the low-mass objects but are ~1 order of magnitude higher than those toward Sgr B2(N2b). This could be due to a warmer pre-stellar phase or a different formation timescale of Sgr B2(N2b). The D/H ratios found from methyl cyanide isotopologues agree well with those of methanol toward BHR71-IRS1, likely pointing to the formation and deuteration of methyl cyanide in a similar star-formation phase as methanol (i.e., the pre-stellar phase). We find an increase in the methyl cyanide D/H ratios with the number of deuterium atoms, which suggests that the deuterated isotopologues may form later in the pre-stellar phase. Future COMPASS studies will increase the sample size of low-mass systems with methyl cyanide analysis and potentially examine some of the trends observed here statistically.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.08754",
  "author_total": 19,
  "authors": [
    {
      "name": "P. Nazari"
    },
    {
      "name": "A. Coutens"
    },
    {
      "name": "J. K. Jørgensen"
    },
    {
      "name": "A. Belloche"
    },
    {
      "name": "A. L. Plunkett"
    },
    {
      "name": "S. Maret"
    },
    {
      "name": "D. Harsono"
    },
    {
      "name": "M. N. Drozdovskaya"
    },
    {
      "name": "J. -E. Lee"
    },
    {
      "name": "F. Cruz-Sáenz de Miera"
    },
    {
      "name": "J. Ferrer Asensio"
    },
    {
      "name": "M. L. R. van 't Hoff"
    },
    {
      "name": "J. -H. Jeong"
    },
    {
      "name": "Á Kóspál"
    },
    {
      "name": "B. A. McGuire"
    },
    {
      "name": "S. Spezzano"
    },
    {
      "name": "Y. -L. Yang"
    },
    {
      "name": "H. -S. Yun"
    },
    {
      "name": "S. Zeng"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/brcrye2b02pzr.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.08754",
  "fulltext_url": null,
  "id": "brcrye2b02pzr",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.08754",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "openalex",
      "3103|Astrophysics and Star Formation Studies"
    ]
  ],
  "openalex": "W7220952464",
  "pdf_url": "https://arxiv.org/pdf/2610.08754",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-06",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/brcrye2b02pzr.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:22Z",
      "native_id": "2610.08754",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.08754"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) -- IV. Methyl cyanide isotopologues toward BHR71-IRS1",
  "title_text": "Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) -- IV. Methyl cyanide isotopologues toward BHR71-IRS1",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:22Z",
  "url": "https://research.draconitic.com/paper/brcrye2b02pzr",
  "venue": "arXiv",
  "versions": []
}