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arXiv 0907.5536astro-ph.HE
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用Gamma-Ray望远镜测量宇宙元素

Measuring Cosmic Elements with Gamma-Ray Telescopes

Roland Diehl

摘要:

伽马射线望远镜能够测量来自宇宙核合成事件的放射性痕量同位素。这样的测量直接针对一些关键同位素,如44 Ti、26 Al、60 Fe和56 Ni,以及β ^+衰变产生的正电子。过去几十年的实验现在已经建立了一个伽马射线线天文学,这是宇宙源核合成环境研究的重要组成部分。对于大质量恒星和超新星,重要的限制已经设定:SN 1987 A中的Co同位素衰变直接证明了核心坍缩超新星中新同位素的合成,来自340岁的Cas A超新星的44 Ti支持富α冻结的概念,但导致理论研究和未来实验的有趣难题。26 Al和60 Fe是从银河系内的叠加核合成中测得的,通过其~ 15%的强度比对双星内部结构进行了限制。26 Al伽马射线线现在被认为可以追踪当前恒星的形成,甚至是整个银河系中星际介质的运动学。在我们银河系的整个平面上,核合成产生的正电子湮灭辐射似乎主要来自26 Al和其他超新星的放射性,但是银河系的隆起区域在正电子湮灭伽马射线中的惊人亮度提出了一个涉及核天体物理学之外的几个天体物理学问题的难题。本文主要讨论大质量恒星核合成中的~(26)Al和~(60)Fe。

英文摘要:

Gamma-ray telescopes are capable of measuring radioactive trace isotopes from cosmic nucleosynthesis events. Such measurements address new isotope production rather directly for a few key isotopes such as 44Ti, 26Al, 60Fe, and 56Ni, as well as positrons from the beta^+-decay variety. Experiments of the past decades have now established an astronomy with gamma-ray lines, which is an important part of the study of nucleosynthesis environments in cosmic sources. For massive stars and supernovae, important constraints have been set: Co isotope decays in SN1987A directly demonstrated the synthesis of new isotopes in core-collapse supernovae, 44Ti from the 340-year old Cas A supernova supports the concept of alpha-rich freeze-out, but results in interesting puzzles pursued by theoretical studies and future experiments. 26Al and 60Fe has been measured from superimposed nucleosynthesis within our Galaxy, and sets constraints on massive-star interior structure through its intensity ratio of ~15%. The 26Al gamma-ray line is now seen to trace current star formation and even the kinematics of interstellar medium throughout the Galaxy. Positron annihilation emission from nucleosynthesis throughout the plane of our Galaxy appears to be mainly from 26Al and other supernova radioactivity, but the striking brightness of the Galaxy's bulge region in positron annihilation gamma-rays presents a puzzle involving several astrophysics issues beyond nuclear astrophysics. This paper focuses mainly on a discussion of 26Al and 60Fe from massive star nucleosynthesis.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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