2017/11/24 by Stéphane Blondin, Luc Dessart, D. John Hillier · 2 citations
Physics and Astronomy · #astro-ph.SR #astro-ph.HE
paper · pdf · doi:10.1093/mnras/stx3058
22 pages, 15 figures. Accepted for publication in MNRAS. The hydrodynamical input and synthetic spectra are available at https://www-n.oca.eu/supernova/home.html
arxiv created 2017/11/24 · arxiv updated 2017/12/27
While Chandrasekhar-mass (M\rm Ch) models with a low 56\rmNi yield can match the peak luminosities of fast-declining, 91bg-like Type Ia supernovae (SNe Ia), they systematically fail to reproduce their faster light-curve evolution. Here we illustrate the impact of a low ejecta mass on the radiative display of low-luminosity SNe Ia, by comparing a sub-M\rm Ch model resulting from the pure central detonation of a C-O White Dwarf (WD) to a M\rm Ch delayed-detonation model with the same 56\rmNi yield of 0.12 M\odot. Our sub-M\rm Ch model from a 0.90 M\odot WD progenitor has a ∼5 day shorter rise time in the integrated UV-optical-IR (uvoir) luminosity, as well as in the B-band, and a ∼20 per cent higher peak uvoir luminosity (∼1 mag brighter peak MB). This sub-M\rm Ch model also displays bluer maximum-light colours due to the larger specific heating rate, and larger post-maximum uvoir and B-band decline rates. The luminosity decline at nebular times is also more pronounced, reflecting the enhanced escape of gamma rays resulting from the lower density of the progenitor WD. The deficit of stable nickel in the innermost ejecta leads to a notable absence of forbidden lines of [Ni II] in the nebular spectra. In contrast, the M\rm Ch model displays a strong line due to [Ni II] 1.939 μ\rmm, which could in principle serve to distinguish between different progenitor scenarios. Our sub-M\rm Ch model offers an unprecedented agreement with optical and near-infrared observations of the 91bg-like SN 1999by, making a strong case for a WD progenitor significantly below the Chandrasekhar-mass limit for this event and other low-luminosity SNe Ia.