{
  "abstract": "We present the luminous, long-lived Type IIn SN 2019qem and use it to reconstruct how much mass its progenitor lost and when. We combine host-subtracted optical and mid-infrared photometry and 26 optical spectra from -22 to +699 d. We model the bolometric light curve with thin-shell CSM-interaction models in REDBACK, with the shock velocity constrained by the H$α$ line widths, and compare them with an analytic interaction model. SN 2019qem rose in $\\approx30$d to $M_I = -20.5$mag and a bolometric peak of $7.0\\times10^{43}$ erg s$^{-1}$, and radiated $6.9\\times10^{50}$ erg in the optical within 575 d, closely resembling luminous, strongly interacting SNe IIn such as SN 2010jl and SN 2015da. A Heii/Niii flash feature at -22 d and unresolved narrow Balmer lines reveal dense, slow CSM. From +78 to +445 d the H$α$ wings are shaped by electron scattering, and the line stays blueshifted by 400-700 km s$^{-1}$, which points to an optically thick, asymmetric interaction region rather than to newly formed dust. In the preferred model, $\\approx7 M_\\odot$ of ejecta run into $\\approx9 M_\\odot$ of gas ejected $\\approx2$ yr before explosion and then into a wind of $\\approx0.6 M_\\odot$ yr$^{-1}$ (for $v_w = 100$ km s$^{-1}$), sweeping up $\\approx32 M_\\odot$ by +544 d. The mid-infrared excess brightens for two years while the optical fades, tracing dust heated by the ongoing interaction. The host is a low-mass, star-forming galaxy, $\\log(M_*/M_\\odot) = 9.19$, with a sub-solar metallicity at the explosion site. In its final decades the progenitor of SN 2019qem lost mass far faster than any steady stellar wind, ending with an eruption of $\\approx9 M_\\odot$ two years before core collapse, consistent with luminous-blue-variable-like eruptive mass loss. Taken at face value, the mass budget implies an initial progenitor mass of $\\gtrsim40 M_\\odot$.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.05328",
  "author_total": 46,
  "authors": [
    {
      "name": "Joysankar Majumdar"
    },
    {
      "name": "Mariusz Gromadzki"
    },
    {
      "name": "Takashi J. Moriya"
    },
    {
      "name": "David A. H. Buckley"
    },
    {
      "name": "Priscila J. Pessi"
    },
    {
      "name": "Nada Ihanec"
    },
    {
      "name": "Szymon Kozłowski"
    },
    {
      "name": "Łukasz Wyrzykowski"
    },
    {
      "name": "Callum Aster"
    },
    {
      "name": "Panos Charalampopoulos"
    },
    {
      "name": "Ting-Wan Chen"
    },
    {
      "name": "Massimo Della Valle"
    },
    {
      "name": "Lluís Galbany"
    },
    {
      "name": "Avishay Gal-Yam"
    },
    {
      "name": "Claudia P. Gutiérrez"
    },
    {
      "name": "Cosimo Inserra"
    },
    {
      "name": "Erkki Kankare"
    },
    {
      "name": "Hanindyo Kuncarayakti"
    },
    {
      "name": "Tomás E. Müller-Bravo"
    },
    {
      "name": "Matt Nicholl"
    },
    {
      "name": "Jacco H. Terwel"
    },
    {
      "name": "David R. Young"
    },
    {
      "name": "Andrzej Udalski"
    },
    {
      "name": "Michał K. Szymański"
    },
    {
      "name": "Igor Soszyński"
    },
    {
      "name": "Paweł Pietrukowicz"
    },
    {
      "name": "Radosław Poleski"
    },
    {
      "name": "Jan Skowron"
    },
    {
      "name": "Krzysztof Ulaczyk"
    },
    {
      "name": "Przemek Mróz"
    },
    {
      "name": "Krzysztof Rybicki"
    },
    {
      "name": "Patryk Iwanek"
    },
    {
      "name": "Marcin Wrona"
    },
    {
      "name": "Mateusz J. Mróz"
    },
    {
      "name": "Moira Andrews"
    },
    {
      "name": "Craig Pellegrino"
    },
    {
      "name": "D. Andrew Howell"
    },
    {
      "name": "Curtis McCully"
    },
    {
      "name": "Daichi Hiramatsu"
    },
    {
      "name": "Megan Newsome"
    },
    {
      "name": "Giacomo Terreran"
    },
    {
      "name": "Estefania Padilla Gonzalez"
    },
    {
      "name": "Joseph R. Farah"
    },
    {
      "name": "Mauritz Wicker"
    },
    {
      "name": "Michał Małkowski"
    },
    {
      "name": "Andrew Fraser Gillan"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9tftaj3wsjzs5.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.05328",
  "fulltext_url": null,
  "id": "9tftaj3wsjzs5",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.05328",
  "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": null,
  "pdf_url": "https://arxiv.org/pdf/2611.05328",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-03",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/9tftaj3wsjzs5.ris",
  "sources": [
    {
      "first_seen": "2026-11-04T15:21:25Z",
      "native_id": "2611.05328",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.05328"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "SN 2019qem: decades of extreme mass loss before the explosion of a luminous, long-lived Type IIn supernova",
  "title_text": "SN 2019qem: decades of extreme mass loss before the explosion of a luminous, long-lived Type IIn supernova",
  "type": "preprint",
  "updated_at": "2026-11-06T18:21:01Z",
  "url": "https://research.draconitic.com/paper/9tftaj3wsjzs5",
  "venue": "arXiv",
  "versions": []
}