The detonation of a sub-Chandrasekhar-mass white dwarf at the origin of the low-luminosity Type Ia supernova 1999by

Abstract

While Chandrasekhar-mass ($M_{\mathrm{Ch}}$) models with a low ${}^{56}\mathrm{Ni}$ 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-$M_{\mathrm{Ch}}$ model resulting from the pure central detonation of a C-O White Dwarf (WD) to a $M_{\mathrm{Ch}}$ delayed-detonation model with the same ${}^{56}\mathrm{Ni}$ yield of 0.12 M${}_{\odot }$. Our sub-$M_{\mathrm{Ch}}$ model from a 0.90 M${}_{\odot }$ WD progenitor has a $\sim$5 day shorter rise time in the integrated UV-optical-IR (uvoir) luminosity, as well as in the $B$-band, and a $\sim$20 per cent higher peak uvoir luminosity ($\sim$1 mag brighter peak $M_B$). This sub-$M_{\mathrm{Ch}}$ 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 $M_{\mathrm{Ch}}$ model displays a strong line due to [Ni II] 1.939 $\mu \mathrm{m}$, which could in principle serve to distinguish between different progenitor scenarios. Our sub-$M_{\mathrm{Ch}}$ 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.

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

References in corpus (10)

• Double-detonation sub-Chandrasekhar supernovae: synthetic observables for minimum helium shell mass models
• The Spectroscopic Diversity of Type Ia Supernovae
• The Initiation and Propagation of Helium Detonations in White Dwarf Envelopes
• The underluminous Type Ia Supernova 2005bl and the class of objects similar to SN 1991bg
• Consistent estimates of (56)Ni yields for type Ia supernovae
• Early 56Ni decay γ-rays from SN2014J suggest an unusual explosion
• Evidence for sub-Chandrasekhar-mass progenitors of Type Ia supernovae at the faint end of the width-luminosity relation
• Ejecta Mass Diagnostics of Type Ia Supernovae
• Near-infrared line identification in type Ia supernovae during the transitional phase
• An exact integral relation between the Ni56 mass and the bolometric light curve of a type Ia supernova

Cited by in corpus (12)

• Sub-Chandrasekhar progenitors favoured for type Ia supernovae: Evidence from late-time spectroscopy
• Monte Carlo radiative transfer for the nebular phase of Type Ia supernovae
• Evidence for Sub-Chandrasekhar Mass Type Ia Supernovae from an Extensive Survey of Radiative Transfer Models
• Delay Time Distributions of Type Ia Supernovae From Galaxy and Cosmic Star Formation Histories
• Carnegie Supernova Project-II: Using Near-Infrared Spectroscopy to determine the location of the outer ${}^{56}$Ni in Type Ia Supernovae
• Spectral signatures of H-rich material stripped from a non-degenerate companion by a Type Ia supernova
• A Physical Basis for the H-band Blue-edge Velocity and Light-Curve Shape Correlation in Context of Type Ia Supernova Explosion Physics
• SN 2012ij: A low-luminosity type Ia supernova and evidence for continuous distribution from 91bg-like explosion to normal ones
• Exploration of Aspherical Ejecta Properties in Type Ia Supernova: Progenitor Dependence and Applications to Progenitor Classification
• Puzzling High-Velocity Calcium Absorption Features Of Type Ia Supernovae
• Revisiting constraints on asymmetric dark matter from collapse in white dwarf stars
• Strong Carbon Features and a Red Early Color in the Underluminous Type Ia SN 2022xkq