{ "abstract": "Context . Methyl cyanide (CH ₃ CN) is one of the most abundant nitrogen-bearing complex organic molecules observed in the gas phase around both 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.\n\nAims . We add to this number by analyzing data toward BHR71-IRS1 taken with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS) Large Program over a ∼33 GHz frequency range.\n\nMethods . 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).\n\nResults . We detect CH ₃ CN, CH ₃ CN v ₈ =1, ¹³ CH ₃ CN, CH ₃ ¹³ CN, CH ₃ C ¹⁵ N, CH ₂ DCN, and CHD ₂ CN. The column density ratio of ¹³ CH ₃ CN/CH ₃ ¹³ CN is around unity, in agreement with previous observations. The CH ₂ DCN/CH ₃ CN 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).\n\nConclusions . 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": [ "European Southern Observatory", "Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS, CNES", "Niels Bohr Institute, University of Copenhagen", "Max-Planck-Institut für Radioastronomie", "National Radio Astronomy Observatory", "Univ. Grenoble Alpes, CNRS, IPAG", "Institute of Astronomy, Department of Physics, National Tsinghua University", "Physikalisch-Meteorologisches Observatorium Davos und Weltstrahlungszentrum (PMOD/WRC)", "Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP), Universität Bern", "Department of Physics and Astronomy, Seoul National University", "Star and Planet Formation Laboratory, RIKEN Pioneering Research Institute, Wako-shi", "Purdue University", "Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences, MTA Centre of Excellence", "Institute of Physics and Astronomy, ELTE Eötvös Loránd University", "Max-Planck-Insitut für Astronomie", "Department of Chemistry, Massachusetts Institute of Technology and National Radio Astronomy Observatory", "Max-Planck-Institut für extraterrestrische Physik" ], "article_type": null, "arxiv": null, "author_total": 19, "authors": [ { "affs": [ 0 ], "name": "P. Nazari", "orcid": "0000-0002-4448-3871" }, { "affs": [ 1 ], "name": "A. Coutens", "orcid": "0000-0003-1805-3920" }, { "affs": [ 2 ], "name": "J. K. Jørgensen", "orcid": "0000-0001-9133-8047" }, { "affs": [ 3 ], "name": "A. Belloche", "orcid": "0000-0003-0046-6217" }, { "affs": [ 4 ], "name": "A. L. Plunkett", "orcid": "0000-0002-9912-5705" }, { "affs": [ 5 ], "name": "S. Maret", "orcid": "0000-0003-1104-4554" }, { "affs": [ 6 ], "name": "D. Harsono", "orcid": "0000-0001-6307-4195" }, { "affs": [ 7, 8 ], "name": "M. N. Drozdovskaya", "orcid": "0000-0001-7479-4948" }, { "affs": [ 9 ], "name": "J.-E. Lee", "orcid": "0000-0003-3119-2087" }, { "affs": [ 1 ], "name": "F. Cruz-Sáenz de Miera", "orcid": "0000-0002-4283-2185" }, { "affs": [ 10 ], "name": "J. Ferrer Asensio", "orcid": "0000-0002-1095-9368" }, { "affs": [ 11 ], "name": "M. L. R. van ’t Hoff", "orcid": "0000-0002-2555-9869" }, { "affs": [ 9 ], "name": "J.-H. Jeong", "orcid": "0009-0005-6319-8485" }, { "affs": [ 12, 13, 14 ], "name": "Á. Kóspál", "orcid": "0000-0001-7157-6275" }, { "affs": [ 4, 15 ], "name": "B. A. McGuire", "orcid": "0000-0003-1254-4817" }, { "affs": [ 16 ], "name": "S. Spezzano", "orcid": "0000-0002-6787-5245" }, { "affs": [ 10 ], "name": "Y.-L. Yang", "orcid": "0000-0001-8227-2816" }, { "affs": [ 9 ], "name": "H.-S. Yun", "orcid": "0000-0001-6842-1555" }, { "affs": [ 10 ], "name": "S. Zeng", "orcid": "0000-0003-3721-374X" } ], "bibtex": "https://research.draconitic.com/paper/88a407w0qhf50.bib", "cited_by": 1, "doi": "10.1051/0004-6361/202558748", "fulltext_url": null, "id": "88a407w0qhf50", "issns": [ "0004-6361", "1432-0746" ], "landing_url": "https://www.aanda.org/10.1051/0004-6361/202558748", "language": null, "licence": "CC-BY-4.0", "licence_label": "CC BY 4.0", "licence_source": "article", "licence_url": "https://creativecommons.org/licenses/by/4.0", "metadata_licence": null, "native_subjects": [ [ "openalex", "3103|Astrophysics and Star Formation Studies" ] ], "openalex": "W7220834962", "pdf_url": null, "pmcid": null, "pmid": null, "published": "2026-10-07", "publisher": "EDP Sciences", "ris": "https://research.draconitic.com/paper/88a407w0qhf50.ris", "sources": [ { "first_seen": "2026-10-30T12:18:18Z", "native_id": "10.1051/0004-6361/202558748", "source": "crossref", "url": "https://www.aanda.org/10.1051/0004-6361/202558748" } ], "subjects": [ { "field": "astronomy", "origin": "openalex:3103|Astrophysics and Star Formation Studies", "subfield": "stellar" } ], "title": "Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)", "title_text": "Complex Organic Molecules in Protostars with ALMA Spectral Surveys (COMPASS)", "type": "peer-reviewed", "updated_at": "2026-10-30T12:18:18Z", "url": "https://research.draconitic.com/paper/88a407w0qhf50", "venue": "Astronomy & Astrophysics", "versions": [] }