SN1991bg-like超新星是银河系大多数反物质的重要来源
SN1991bg-like supernovae are a compelling source of most Galactic antimatter
摘要：
银河系闪烁着柔和的伽马射线，这是每秒$\sim 5 \times 10^{43}$正负电子对湮灭的结果。大量反物质的起源和湮灭产生的511 keV伽马射线线的特殊形态已经成为近半个世纪的争论主题。大多数明显的正电子源都与恒星形成区有关，无法解释银河系核球中正电子湮灭的速率，而核球中最后一次看到恒星形成是在$10\,\mathrm{Gyr}$之前，否则就违反了对正电子注入能量的严格限制。在核心坍缩超新星（CCSNe）和正常Ia型超新星（SNe Ia）中形成的元素的放射性衰变可以提供与注入能量约束相匹配的正电子，但这种潜在来源的分布并不能复制所需的形态。我们发现，一类特殊的热核超新星-SN 1991 bg类超新星（SNe 91 bg）-可以提供的正电子的数量和分布，我们看到在银河系中通过衰变的$^{44}$ Ti在这些事件中合成的湮灭。这种$^{44}$ Ti的产生同时解决了在太阳系材料中观测到的$^{44}$ Ti衰变产物$^{44}$ Ca的丰度。
英文摘要：
The Milky Way Galaxy glows with the soft gamma ray emission resulting from the annihilation of $\sim 5 \times 10^{43}$ electron-positron pairs every second. The origin of this vast quantity of antimatter and the peculiar morphology of the 511keV gamma ray line resulting from this annihilation have been the subject of debate for almost half a century. Most obvious positron sources are associated with star forming regions and cannot explain the rate of positron annihilation in the Galactic bulge, which last saw star formation some $10\,\mathrm{Gyr}$ ago, or else violate stringent constraints on the positron injection energy. Radioactive decay of elements formed in core collapse supernovae (CCSNe) and normal Type Ia supernovae (SNe Ia) could supply positrons matching the injection energy constraints but the distribution of such potential sources does not replicate the required morphology. We show that a single class of peculiar thermonuclear supernova - SN1991bg-like supernovae (SNe 91bg) - can supply the number and distribution of positrons we see annihilating in the Galaxy through the decay of $^{44}$Ti synthesised in these events. Such $^{44}$Ti production simultaneously addresses the observed abundance of $^{44}$Ca, the $^{44}$Ti decay product, in solar system material.
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