SN 2019qem: decades of extreme mass loss before the explosion of a luminous, long-lived Type IIn supernova
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 Hα line widths, and compare them with an analytic interaction model. SN 2019qem rose in ≈30d to MI = −20.5mag and a bolometric peak of 7.0×1043 erg s−1, and radiated 6.9×1050 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 Hα 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, ≈7 M⊙ of ejecta run into ≈9 M⊙ of gas ejected ≈2 yr before explosion and then into a wind of ≈0.6 M⊙ yr−1 (for vw = 100 km s−1), sweeping up ≈32 M⊙ 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⊙) = 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 ≈9 M⊙ 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 ≳40 M⊙.
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BibTeX
@misc{majumdar20262019qem,
title = {{SN 2019qem: decades of extreme mass loss before the explosion of a luminous, long-lived Type IIn supernova}},
author = {Joysankar Majumdar and Mariusz Gromadzki and Takashi J. Moriya and David A. H. Buckley and Priscila J. Pessi and Nada Ihanec and Szymon Kozłowski and Łukasz Wyrzykowski and Callum Aster and Panos Charalampopoulos and Ting-Wan Chen and Massimo Della Valle and Lluís Galbany and Avishay Gal-Yam and Claudia P. Gutiérrez and Cosimo Inserra and Erkki Kankare and Hanindyo Kuncarayakti and Tomás E. Müller-Bravo and Matt Nicholl and Jacco H. Terwel and David R. Young and Andrzej Udalski and Michał K. Szymański and Igor Soszyński and Paweł Pietrukowicz and Radosław Poleski and Jan Skowron and Krzysztof Ulaczyk and Przemek Mróz and Krzysztof Rybicki and Patryk Iwanek and Marcin Wrona and Mateusz J. Mróz and Moira Andrews and Craig Pellegrino and D. Andrew Howell and Curtis McCully and Daichi Hiramatsu and Megan Newsome and Giacomo Terreran and Estefania Padilla Gonzalez and Joseph R. Farah and Mauritz Wicker and Michał Małkowski and Andrew Fraser Gillan},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.05328},
eprint = {2611.05328},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.05328},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - SN 2019qem: decades of extreme mass loss before the explosion of a luminous, long-lived Type IIn supernova
AU - Joysankar Majumdar
AU - Mariusz Gromadzki
AU - Takashi J. Moriya
AU - David A. H. Buckley
AU - Priscila J. Pessi
AU - Nada Ihanec
AU - Szymon Kozłowski
AU - Łukasz Wyrzykowski
AU - Callum Aster
AU - Panos Charalampopoulos
AU - Ting-Wan Chen
AU - Massimo Della Valle
AU - Lluís Galbany
AU - Avishay Gal-Yam
AU - Claudia P. Gutiérrez
AU - Cosimo Inserra
AU - Erkki Kankare
AU - Hanindyo Kuncarayakti
AU - Tomás E. Müller-Bravo
AU - Matt Nicholl
AU - Jacco H. Terwel
AU - David R. Young
AU - Andrzej Udalski
AU - Michał K. Szymański
AU - Igor Soszyński
AU - Paweł Pietrukowicz
AU - Radosław Poleski
AU - Jan Skowron
AU - Krzysztof Ulaczyk
AU - Przemek Mróz
AU - Krzysztof Rybicki
AU - Patryk Iwanek
AU - Marcin Wrona
AU - Mateusz J. Mróz
AU - Moira Andrews
AU - Craig Pellegrino
AU - D. Andrew Howell
AU - Curtis McCully
AU - Daichi Hiramatsu
AU - Megan Newsome
AU - Giacomo Terreran
AU - Estefania Padilla Gonzalez
AU - Joseph R. Farah
AU - Mauritz Wicker
AU - Michał Małkowski
AU - Andrew Fraser Gillan
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2611.05328
UR - https://arxiv.org/abs/2611.05328
AB - 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 Hα line widths, and compare them with an analytic interaction model. SN 2019qem rose in ≈30d to M_I = −20.5mag and a bolometric peak of 7.0×10^43 erg s^−1, and radiated 6.9×10^50 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 Hα 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, ≈7 M_⊙ of ejecta run into ≈9 M_⊙ of gas ejected ≈2 yr before explosion and then into a wind of ≈0.6 M_⊙ yr^−1 (for v_w = 100 km s^−1), sweeping up ≈32 M_⊙ 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_⊙) = 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 ≈9 M_⊙ 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 ≳40 M_⊙.
ER -