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arXiv 0903.0772astro-ph.HEastro-ph.GA
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宇宙核的Gamma-Ray谱线研究

Gamma-Ray Line Studies of Nuclei in the Cosmos

M. Leising, R. Diehl

摘要:

伽马射线谱线研究能够确定宇宙核合成事件中产生的放射性示踪同位素。30年前,HEAO-C1进行了开创性的测量,探测到了来自26 Al的第一条星际伽马射线线,然后是SMM和许多气球实验,其中包括超新星SN 1987 A的放射性探测,康普顿天文台及其OSSE和COMPTEL仪器在1991-2000年进行了测量。该卫星进行了26 Al和511 keV湮灭发射的巡天观测,并探测了44 Ti放射性的Cas A超新星遗迹。INTEGRAL上的SPI高分辨率Ge光谱仪于2002年发射,并继续收集来自44 Ti,26 Al,60 Fe衰变和正电子湮灭的天体物理学重要伽马射线线的数据。两台INTEGRAL望远镜都观测到了来自Cas A的44 Ti衰变线,并限制了喷出物的膨胀动力学。缺乏其他44 Ti残留物是一个谜。26 Al伽马射线线现在在整个银河系中被测量,追踪大质量恒星附近星际气体的运动学,并突出其中的特殊区域,例如天鹅座的大质量恒星群和更多附近的区域。在26 Al通量的15%水平下检测60 Fe放射性线对观测者和模型都提出了挑战。银河平面内核合成区域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,而隆起的正电子湮灭亮度仍然令人困惑。

英文摘要:

Gamma-ray line studies are capable of identifying radioactive tracer isotopes generated in cosmic nucleosynthesis events. Pioneering measurements were made 30 years ago with HEAO-C1, detecting the first interstellar gamma-ray line from 26Al, then with SMM and numerous balloon experiments, among their results the detection of radioactivity from supernova SN1987A, and with the Compton Observatory and its OSSE and COMPTEL instruments in 1991-2000, which performed sky surveys in 26Al and 511 keV annihilation emission and the detection of the Cas A supernova remnant in 44Ti radioactivity. The SPI high-resolution Ge spectrometer on INTEGRAL was launched in 2002 and continues to collect data on astrophysically-important gamma-ray lines from decays of 44Ti, 26Al, 60Fe, and positron annihilation. 44Ti decay lines from Cas A have been observed with both INTEGRAL telescopes, and constrain the expansion dynamics of the ejecta. The lack of other 44Ti remnants is a mystery. The 26Al gamma-ray line is now measured throughout the Galaxy, tracing the kinematics of interstellar gas near massive stars, and highlighting special regions of interest therein, such as groups of massive stars in Cygnus and even more nearby regions. The detection of 60Fe radioactivity lines at the level of 15% of the 26Al flux presents a challenge both for observers and models. Positron annihilation emission from the nucleosynthesis regions within the Galactic plane appears to be mainly from 26Al and other supernova radioactivity, while the bulge's positron annihilation brightness remains puzzling.

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