白矮星上现实未扰动氦壳的流驱动点火
Stream-Driven Ignition of a Realistic Undisturbed Helium Shell on a White Dwarf
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中文总结 AI 辅助
研究白矮星上氦壳流驱动点火，用FLASH二维模拟不同质量白矮星及流特性，发现流冲击能致氦点火，点火位置在核壳过渡附近，不同模型点火机制有别，多数模型有传播爆轰，强化了D$^6$模型作为Ia型超新星前身模型的可行性。
中文摘要 AI 辅助
动态驱动的双简并双爆轰（D$^6$）模型已成为Ia型超新星有前景的前身模型。在该模型中，紧密双白矮星双星系统中的碳氧白矮星，通过其伴星的动态质量转移引发双爆轰。质量转移流直接冲击主白矮星表面，可能点燃表层氦爆轰。此前研究虽证明该机制可行，但氦壳点火条件仍不确定。我们用FLASH进行二维模拟，研究流冲击对具有现实未混合成分分布的碳氧白矮星的氦爆轰点火情况。对质量为0.8、0.9和1.0$M_\odot$的白矮星建模，并改变每种情况下的流特性。结果发现流冲击在所有情况下都导致氦点火，点火发生在距冲击点不同距离处，且一致发生在核壳过渡附近。不过，不同模型的点火机制不同，可能源于相邻热混合区域的相互作用而非单点。最终，除一个模型外，所有模型都维持了能穿越白矮星表面的传播爆轰，进一步强化了D$^6$模型作为Ia型超新星前身模型的可行性。
英文摘要
The dynamically driven double degenerate double detonation (D$^6$) model has emerged as a promising progenitor scenario for Type Ia supernovae. In this model, a carbon-oxygen white dwarf (WD) in a close double WD binary undergoes a double-detonation triggered by dynamical mass transfer from its companion. The mass transfer stream directly impacts the surface of the primary WD, potentially igniting a helium detonation in the surface layer. The resulting shock converges in the core, triggering a carbon detonation that ultimately unbinds the star. While previous studies have demonstrated the viability of this mechanism, the conditions under which the helium shell ignites remain uncertain. We perform two-dimensional simulations using FLASH to study helium detonation ignition driven by stream impact on a carbon-oxygen WD with a realistic, unmixed composition profile left at the end of the previous helium-shell burning phase before the WD was formed. We model WDs with masses of 0.8, 0.9, and 1.0 $,M_\odot$ and vary stream properties for each case. We find that stream impact leads to helium ignition in all cases, with ignition occurring at varying distances from the impact point. Ignition consistently occurs near the core-shell transition, highlighting the importance of a realistic WD profile. However, the ignition mechanism differs between models and can arise from interactions of neighboring hot, mixed regions rather than a single point. Ultimately, all models but one sustain a propagating detonation capable of traversing the WD surface further reinforcing the viability of the D$^6$ model as a progenitor scenario for Type Ia supernovae.
