[Paper Review] An Alternative Symbiotic Channel to Type Ia Supernovae

Guoliang Lv, Chunhua Zhu+2 more|ArXiv.org|Mar 15, 2009

Gamma-ray bursts and supernovae2 references4 citations

TL;DR

This paper proposes an alternative symbiotic channel for Type Ia supernovae (SNe Ia) in which a red giant donor with an aspherical stellar wind and dense equatorial disk enables stable mass transfer to a carbon-oxygen white dwarf, avoiding common envelope phases. The model predicts a Galactic birthrate of 1.03×10⁻³ to 2.27×10⁻⁵ yr⁻¹ and delay times from 0.07 to 5 Gyr, with progenitors of SN 2006X and SN 2002ic explained by dust in equatorial disks swept by ejecta.

ABSTRACT

By assuming an aspherical stellar wind with an equatorial disk from a red giant, we investigate the production of Type Ia supernovae (SNe Ia) via symbiotic channel. We estimate that the Galactic birthrate of SNe Ia via symbiotic channel is between $1.03 imes 10^{-3}$ and $2.27 imes 10^{-5}$ yr$^{-1}$, the delay time of SNe Ia has wide range from $\sim$ 0.07 to 5 Gyr. The results are greatly affected by the outflow velocity and mass-loss rate of the equatorial disk. Using our model, we discuss the progenitors of SN 2002ic and SN 2006X.

Motivation & Objective

• To investigate whether an aspherical stellar wind with an equatorial disk in symbiotic red giant systems can enable stable mass transfer to a white dwarf, avoiding common envelope phases.
• To assess the viability of this channel as a significant source of Type Ia supernovae, given the low birthrates predicted by standard models.
• To explain the observed circumstellar (CS) environments of SNe Ia like SN 2006X and SN 2002ic, particularly the presence of low-velocity Na I absorption and dust with small grain sizes.
• To quantify the Galactic birthrate and delay time distribution of SNe Ia via this alternative symbiotic channel under varying wind parameters.
• To identify plausible progenitor systems for SN 2006X and SN 2002ic based on mass-loss rates, wind anisotropy, and prior thermonuclear outbursts.

Proposed method

• Adopts a rapid binary evolution code (Hurley et al. 2002) to model the evolution of WD+RG systems, with the secondary evolving into the first giant branch (FGB) or asymptotic giant branch (AGB) phase.
• Introduces an aspherical stellar wind model with enhanced mass-loss in the equatorial plane, based on observed higher mass-loss rates and rotational velocities in symbiotic giants compared to field giants.
• Uses observational constraints from radio, mm/submm, and IRAS data to estimate enhanced mass-loss rates (3–30× higher than field giants) and equatorial wind density.
• Models the interaction between high-velocity ejecta from mild hydrogen-shell burning events and the dense equatorial disk, simulating dust grain size reduction and slow-down of ejecta.
• Performs population synthesis to estimate the Galactic birthrate and delay time distribution of SNe Ia via this channel, varying outflow velocity and mass-loss rate.
• Compares model predictions with observational features of SN 2006X (low-velocity Na I absorption, multiple dust shells) and SN 2002ic (CS environment), identifying progenitor candidates.

Experimental results

Research questions

• RQ1 Can an aspherical stellar wind with an equatorial disk in a symbiotic red giant stabilize mass transfer to a white dwarf, preventing common envelope ejection?
• RQ2 What is the predicted Galactic birthrate of SNe Ia via this alternative symbiotic channel, and how does it compare to observed rates?
• RQ3 How do variations in equatorial wind outflow velocity and mass-loss rate affect the delay time distribution of SNe Ia in this channel?
• RQ4 Can the observed circumstellar environment of SN 2006X—characterized by low-velocity Na I absorption and small-grain dust—be explained by a dense equatorial disk swept by prior outbursts?
• RQ5 What progenitor configurations best reproduce the observational features of SN 2002ic, particularly its CS environment?

Key findings

• The Galactic birthrate of SNe Ia via the proposed symbiotic channel ranges from 1.03×10⁻³ yr⁻¹ (case 2) to 2.27×10⁻⁵ yr⁻¹ (case 6), depending on wind parameters.
• The delay time between binary formation and SN Ia explosion spans a wide range, from ∼0.07 to 5 Gyr, with results highly sensitive to equatorial wind outflow velocity and mass-loss rate.
• The progenitor of SN 2006X is best explained by a WD+RG system with a dense equatorial disk and prior mild hydrogen-shell burning events, where ejecta sweep and slow down dust in the disk.
• The circumstellar environment of SN 2006X, including low-velocity Na I absorption and multiple dust shells with small grain sizes, is consistent with dust formation and processing in the equatorial disk.
• The progenitor of SN 2002ic is likely a WD+RG system with a dense equatorial disk, and its CS environment originates primarily from this disk material.
• The model suggests that SNe Ia like SN 2006X are rare events, with individual case birthrates ranging from ∼0 to 2.5×10⁻⁵ yr⁻¹, with case 2 yielding the highest rate at 2.5×10⁻⁵ yr⁻¹.