Uncertainties and robustness of the ignition process in type Ia supernovae

Abstract

Context. It is widely accepted that the onset of the explosive carbon burning in the core of a carbon-oxygen white dwarf (CO WD) triggers the ignition of a type Ia supernova (SN Ia). The features of the ignition are among the few free parameters of the SN Ia explosion theory. Aims. We explore the role for the ignition process of two different issues: firstly, the ignition is studied in WD models coming from different accretion histories. Secondly, we estimate how a different reaction rate for C-burning can affect the ignition. Methods. Two-dimensional hydrodynamical simulations of temperature perturbations in the WD core ("bubbles") are performed with the FLASH code. In order to evaluate the impact of the C-burning reaction rate on the WD model, the evolution code FLASH_THE_TORTOISE from Lesaffre et al. (2006, MNRAS, 368, 187) is used. Results. In different WD models a key role is played by the different gravitational acceleration in the progenitor's core. As a consequence, the ignition is disfavored at a large distance from the WD center in models with a larger central density, resulting from the evolution of initially more massive progenitors. Changes in the C reaction rate at T < ∼ 5 × 10 8 K slightly influence the ignition density in the WD core, while the ignition temperature is almost unaffected. Recent measurements of new resonances in the C-burning reaction rate (Spillane et al. 2007, Phys. Rev. Lett., 98, 122501) do not affect the core conditions of the WD significantly.Conclusions. This simple analysis, performed on the features of the temperature perturbations in the WD core, should be extended in the framework of the state-of-the-art numerical tools for studying the turbulent convection and ignition in the WD core. Future measurements of the C-burning reactions cross section at low energy, though certainly useful, are not expected to affect our current understanding of the ignition process dramatically.

Type Ia supernovae and the12C+12C reaction rate

“…With such a resonance, even of moderate strength, bubbles run away closer to the center than predicted by using the CF88 rate (see also Iapichino & Lesaffre 2010). On the other hand, if the resonance were strong enough to provoke an offcenter ignition, it would have the opposite effect.…”

“…Cooper et al (2009) studied the changes induced by such a resonance on the physics of superburst ignition on accreting neutron star crusts. Bennett et al (2010a) and Bennett et al (2010b) explored the impact on the s-process induced by an increase in the carbon fusion reaction rate up to a factor 50 000 at T = 5 × 10 8 K. Finally, Iapichino & Lesaffre (2010) analyzed the influence of uncertainties in the 12 C + 12 C reaction at T 5 × 10 8 K on the ignition of the WD core. They found that the ignition density depends slightly on the presence of a low-energy resonance while the ignition temperature is almost unaffected.…”

Plasma effects on resonant fusion

“…We also note recent considerations of the role of a possible 1 2C+ 1 2C resonance on the ignition of a type 1a supernovae [15] [16]. Though screening issues were not addressed in either of these works, the plasma coupling is strong enough in this application that they need to be.…”

Simplified Hydrostatic Carbon Burning in White Dwarf Interiors

“…These efforts have been accompanied by new developments in the physics of the explosion which have shown that even if pure deflagration models can reproduce many SN Ia spectra and light curves , in some cases a delayed detonation may be necessary (Khokhlov 1991;Röpke et al 2007). The physics of both the transition to detonation and ignition of the deflagration wave remains uncertain (Iapichino et al 2006;Röpke 2007;Iapichino & Lesaffre 2010).…”

“…We foresee the application of these simplified networks or their modification in detailed one or multi-dimensional stellar evolution models trying to understand presupernova CO WDs or similar objects (see, e.g., Lesaffre et al 2006;Zingale et al 2009;Iapichino & Lesaffre 2010). …”