[论文解读] Type Ia Supernovae Can Arise from the Detonations of Both Stars in a Double Degenerate Binary

Samuel J. Boos, Dean M. Townsley+1 more|arXiv (Cornell University)|Jan 15, 2024

Gamma-ray bursts and supernovae被引用 4

一句话总结

本论文通过二维流体动力学模拟表明，双白矮星双星系统中可能通过连续爆轰产生Ia型超新星，其中主星白矮星经历双爆轰，触发伴星的二次爆轰。尽管抛射物质量与元素丰度显著不同，但这些三重与四重爆轰情景的合成光曲线和光谱与观测到的Ia型超新星以及孤立双爆轰模型的匹配程度相当。

ABSTRACT

The precise origin of Type Ia supernovae (SNe Ia) is unknown despite their value to numerous areas in astronomy. While it is a long-standing consensus that they arise from an explosion of a carbon/oxygen white dwarf, the exact progenitor configurations and explosion mechanisms that lead to SNe Ia are still debated. One popular theory is the double detonation in which a helium layer, accreted from a binary companion, detonates on the surface of the primary star, leading to a converging shock-induced detonation of the underlying core. It has recently been seen in simulations that a helium-rich degenerate companion may undergo its own explosion triggered by the impact from the ejecta of the primary star. We show 2D simulations that approximate a white dwarf undergoing a double detonation which triggers the explosion of the degenerate companion, leading to either a triple or quadruple detonation. We also present the first multi-dimensional radiative transfer results from the triple and quadruple detonation scenario. We find that within a range of mass configurations of the degenerate binary, the synthetic light curves and spectra of these events match observations as well as theoretical models of isolated double detonations do. Notably, double and quadruple detonations that are spectrally similar and reach the same peak brightnesses have drastically different ejection masses and produce different amounts of Si- and Fe-group elements. Further understanding of this scenario is needed in order to determine if at least some observed SNe Ia actually originate from two stars exploding.

研究动机与目标

• 研究双白矮星双星系统中两颗恒星是否均可经历爆轰，从而导致Ia型超新星的产生。
• 确定由此产生的合成观测量——光曲线与光谱——是否能与观测到的Ia型超新星以及孤立双爆轰模型相匹配。
• 探讨伴星爆轰对抛射物质量、元素丰度及星云相特征的影响。
• 评估该双星爆炸情景作为Ia型超新星可行爆发通道的可行性，特别是解释观测数据中的离散性与特殊特征。
• 为未来非-LTE辐射转移与三维模拟奠定基础，以区分此情景与其他Ia型超新星前身星模型。

提出的方法

• 使用FLASH代码进行二维模拟，以模拟碳氧白矮星经历双爆轰的流体动力学过程。
• 追踪爆轰波在主星核心的传播及其对致密伴星的影响。
• 模拟伴星随后发生的爆轰，形成三重或四重爆轰情景。
• 利用Sedona代码进行多维辐射转移计算，生成爆炸后约50天内的合成光曲线与光谱。
• 通过改变前身星质量配置（如0.40 M☉的氦伴星、0.90 M☉的CO主星）探索参数空间，并评估观测上的简并性。
• 将合成观测结果与观测到的Ia型超新星进行比较，包括峰值亮度、衰减率及光谱特征，以评估模型的保真度。

Figure 1: Multiband light curves from the detonation of an isolated 1.00 $M_{\odot}$ WD, compared with that of a double detonation of a thin helium shell 1.02 $M_{\odot}$ WD (Boos et al., 2021 ; Shen et al., 2021b ) . Three lines of sight from each model are shown, where the dotted, solid, and dashe

实验结果

研究问题

• RQ1 在双白矮星双星系统中，主星白矮星的双爆轰是否能触发其致密伴星的二次爆轰？
• RQ2 此类双星爆炸情景的合成光曲线与光谱是否能与观测到的Ia型超新星以及孤立双爆轰模型相匹配？
• RQ3 在观测特征相似的情况下，单星与双星爆炸情景在抛射物质量与元素丰度（特别是56Ni、56Fe与40Ca）方面有何差异？
• RQ4 在星云相中，单爆轰与双爆轰情景之间可能在铁群元素分布上产生何种可观测差异？
• RQ5 该情景能否解释星云光谱中观测到的双峰Fe线特征，如Dong等人（2015）报告的5,000 km s⁻¹的峰值分离？

主要发现

• 三重与四重爆轰情景产生的合成光曲线与光谱与观测到的Ia型超新星的匹配程度与孤立双爆轰模型相当。
• 尽管峰值亮度与光谱形态相似，双星爆炸情景的抛射物质量显著不同——例如，四重爆轰情形下伴星质量为0.40 M☉，远高于孤立模型。
• 双星情景导致截然不同的核合成产物：0.40 M☉的氦伴星残留0.16 M☉未燃烧的氦，且总56Ni与56Fe产量与孤立双爆轰模型存在显著差异。
• 模型显示核心抛射物丰度具有非单调分层结构，可能在星云相导致可观测差异，包括双峰Fe线特征。
• 该情景可产生沿视线方向高质质量物质的双峰分布，可能解释部分Ia型超新星中观测到的双峰Fe线，如Dong等人（2015）所报告。
• 完整的后处理核合成产物、抛射物分布与合成光谱已公开发布于Zenodo（10.5281/zenodo.10515767），可供进一步分析与比较。

Figure 2: Spectral comparison between the 1.02 $M_{\odot}$ shelled double detonation model from Boos et al. ( 2021 ) and a bare 1.00 $M_{\odot}$ C/O WD 42 o above the equatorial plane, the line of sight at which these models disagree the most. Each pair of spectra are at the labeled time relative to