arXiv 2601.071512026-01-12astro-ph.SR

缓慢白矮星并合作为银河系中重于铁元素的新来源

Slow White Dwarf Mergers as a New Galactic Source of Trans-Iron Elements

University of Hull（赫尔大学）；University of Edinburgh（爱丁堡大学）；INFN - Istituto Nazionale Fisica Nucleare（意大利国家核物理研究所）；Heidelberg Institute for Theoretical Studies（海德尔堡理论研究所）

Umberto Battino, Claudia Lederer-Woods, Claudia Travaglio, Friedrich Konrad Röpke, Brad Gibson

备注：: Published on EPJ Web of Conferences
发表信息：: EPJ Web of Conferences 260, 06002 (2022)
DOI：: 10.1051/epjconf/202226006002

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AI总结：

研究显示，缓慢白矮星并合可通过延迟爆轰或纯爆轰机制，高效产生重于铁的元素，如p过程同位素和s过程元素。

摘要：

当今太阳系中观测到的最重稳定元素的天体物理起源仍然不完全清楚。最近的研究表明，双星系统中吸积氢的白矮星（WDs）在作为Ia型超新星爆发时，可能成为铁以外的高效p过程源。然而，观测证据和恒星模型都挑战了这些事件所需的频率。在本工作中，我们计算了缓慢并合碳氧白矮星的演化和核合成。当我们的模型接近钱德勒质量时，并合阶段中，22Ne(a,n)25Mg中子源反应在主白矮星的外部层被激活，其中从次级白矮星摄取的碳富材料通过12C+12C反应燃烧，这通过12C(12C,α)20Ne通道提供必要的α粒子。所得到的中子捕获丰度分布与弱s过程相似，峰值在锆，比太阳高30倍。最外层富含第一峰s过程元素的质量关键地取决于12C+12C反应率，范围在0.05个太阳质量到约0.1个太阳质量之间。这些结果表明，如果通过延迟爆轰机制爆炸，缓慢白矮星并合可以高效产生轻p过程同位素（如74Se、78Kr、84Sr、92Mo和94Mo）通过γ诱导反应；或者在纯爆轰情况下，将未燃烧的外部层中富含第一峰s过程元素的高浓度物质抛射出去。在两种情况下，我们首次提出，双星系统中的缓慢白矮星并合可能是重于铁元素的新相关来源。

英文摘要：

The astrophysical origins of the heaviest stable elements that we observe today in the Solar System are still not fully understood. Recent studies have demonstrated that H-accreting white dwarfs (WDs) in a binary sys- tem exploding as type Ia supernovae could be an efficient p-process source beyond iron. However, both observational evidence and stellar models challenge the required frequency of these events. In this work, we calculate the evolution and nucleosynthesis in slowly merging carbon-oxygen WDs. As our models approach the Chandrasekhar mass during the merger phase, the 22Ne(a,n)25Mg neutron source reaction is activated in the external layers of the primary WD, where the carbon-rich material accreted from the secondary WD is burned via the 12C+12C reaction, which provides the necessary α-particles via the 12C(12C,α)20Ne channel. The resulting neutron capture abundance distribution closely resembles a weak s-process one and peaks at Zr, which is overpro- duced by a factor of 30 compared to solar. The mass of the most external layers enriched in first-peak s-process elements crucially depends on the 12C+12C re- action rate, ranging between 0.05 Msun and ~0.1 Msun. These results indicate that slow white dwarf mergers can efficiently produce the lightest p-process iso- topes (such as 74Se, 78Kr, 84Sr, 92Mo and 94Mo) via γ-induced reactions if they explode via a delayed detonation mechanism, or eject the unburned external layers highly enriched in first peak s-process elements in the case of a pure deflagration. In both cases, we propose for the first time that slow WD mergers in binary systems may be a new relevant source for elements heavier than iron.

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