@misc{10481/69454,
year = {2021},
month = {5},
url = {http://hdl.handle.net/10481/69454},
abstract = {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 (~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 (lesssim−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, 56Ni 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 56Ni masses (gsim0.05 M⊙), 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 (MZAMS sime 18–22 M⊙) with small H-rich envelope masses (${M}_{{{\rm{H}}}_{\mathrm{env}}}\simeq 1.7\,{M}_{\odot }$) that have experienced enhanced mass loss ($\dot{M}\simeq {10}^{-2}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$) 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.},
publisher = {IOP Publishing},
keywords = {Supernovae},
keywords = {Core-collapse supernovae},
keywords = {Type II supernovae},
keywords = {Massive stars},
keywords = {Red supergiant stars},
title = {Luminous Type II Short-Plateau Supernovae 2006Y, 2006ai, and 2016egz: A Transitional Class from Stripped Massive Red Supergiants},
doi = {10.3847/1538-4357/abf6d6},
author = {Hiramatsu, Daichi and Galbany González, Lluis},
}