Refereed journal article or data article (A1)

Luminous Type II Short-Plateau Supernovae 2006Y, 2006ai, and 2016egz: A Transitional Class from Stripped Massive Red Supergiants

List of Authors: Hiramatsu Daichi, Howell D Andrew, Moriya Takashi J, Goldberg Jared A, Hosseinzadeh Griffin, Arcavi Iair, Anderson Joseph P, Gutíerrez Claudia P, Burke Jamison, McCully Curtis, Valenti Stefano, Galbany Lluís, Fang Qiliang L, Maeda Keiichi, Folatelli Gastón, Hsiao Eric Y, Morrell Nidia, Phillips Mark M, Stritzinger Maximilian D, Suntzeff Nicholas B, Gromadzki Mariuz, Maguire Kate, Müller-Bravo Tomás E, Young David R


Publication year: 2021

Journal: Astrophysical Journal

Journal name in source: ASTROPHYSICAL JOURNAL

Journal acronym: ASTROPHYS J

Volume number: 913

Issue number: 1

Number of pages: 21

ISSN: 0004-637X

eISSN: 1538-4357



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The diversity of Type II supernovae (SNe II) is thought to be driven mainly by differences in their progenitor's hydrogen-rich (H-rich) envelope mass, with SNe IIP having long plateaus (similar to 100 days) and the most massive H-rich envelopes. However, it is an ongoing mystery why SNe II with short plateaus (tens of days) are rarely seen. Here, we present optical/near-infrared photometric and spectroscopic observations of luminous Type II short-plateau SNe 2006Y, 2006ai, and 2016egz. Their plateaus of about 50-70 days and luminous optical peaks (less than or similar to-18.4 mag) indicate significant pre-explosion mass loss resulting in partially stripped H-rich envelopes and early circumstellar material (CSM) interaction. We compute a large grid of MESA+STELLA single-star progenitor and light-curve models with various progenitor zero-age main-sequence (ZAMS) masses, mass-loss efficiencies, explosion energies, Ni-56 masses, and CSM densities. Our model grid shows a continuous population of SNe IIP-IIL-IIb-like light-curve morphology in descending order of H-rich envelope mass. With large Ni-56 masses (greater than or similar to 0.05M(circle dot)), short-plateau SNe II lie in a confined parameter space as a transitional class between SNe IIL and IIb. For SNe 2006Y, 2006ai, and 2016egz, our findings suggest high-mass red supergiant (RSG) progenitors (M-ZAMS similar or equal to 18-22M(circle dot)) with small H-rich envelope masses (M-Henv similar or equal to 1.7 M-circle dot) that have experienced enhanced mass loss (M similar or equal to 10(-2) M-circle dot yr(-1)) for the last few decades before the explosion. If high-mass RSGs result in rare short-plateau SNe II, then these events might ease some of the apparent underrepresentation of higher-luminosity RSGs in observed SN II progenitor samples.

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Last updated on 2022-07-10 at 12:44