一个天体gamma-ray前景,由于太阳系小天体的碰撞和星际cosmic ray光谱的远程探测
A celestial gamma-ray foreground due to the albedo of small solar system bodies and a remote probe of the interstellar cosmic ray spectrum
摘要:
以月球为模板,计算了宇宙射线与主带小行星(MBA)、木星和海王星特洛伊小行星以及柯伊伯带天体(KBO)中固体岩石和冰相互作用的γ射线辐射通量。我们发现,主带,特洛伊和柯伊伯带的伽玛射线的辐射强度强烈依赖于每个系统的小天体尺寸分布。基于对高能伽马射线实验望远镜(EGRET)数据的分析,我们推断来自MBA、特洛伊和KBO的漫射辐射的积分通量小于~ 6 × 10 ^{-6} cm^{-2} s^{-1}(100-500 MeV),相当于月球辐射的~12倍,并且可能被即将到来的伽马射线大面积空间望远镜(GLAST)探测到。如果被GLAST检测到,它可以提供关于每个系统中小天体数量的独特直接信息,这是任何其他方法都难以评估的。此外,KBO的质子通量可以用来探测在接近星际条件下的CR核的光谱。MBA、特洛伊和KBO的轨道分布在黄道附近,黄道穿过银河系中心和高银河系纬度。因此,在分析黄道附近的弱伽马射线源时,特别是在银河系中心附近,以及在银河系高纬度地区的信号,如河外伽马射线发射时,必须考虑小行星伽马射线的辐射。由于次级正电子在岩石中湮灭,小行星的电子能谱也显示出511 keV的谱线。这可能是一个重要的和以前未认识到的天体前景的INTERNATIONAL伽马射线天体物理实验室(INTEGRAL)的银河系511千电子伏线发射的观测,包括银河系中心的方向。
英文摘要:
We calculate the gamma-ray albedo flux from cosmic-ray (CR) interactions with the solid rock and ice in Main Belt asteroids (MBAs), Jovian and Neptunian Trojan asteroids, and Kuiper Belt objects (KBOs) using the Moon as a template. We show that the gamma-ray albedo for the Main Belt, Trojans, and Kuiper Belt strongly depends on the small-body size distribution of each system. Based on an analysis of the Energetic Gamma Ray Experiment Telescope (EGRET) data we infer that the diffuse emission from the MBAs, Trojans, and KBOs has an integrated flux of less than ~6x10^{-6} cm^{-2} s^{-1} (100-500 MeV), which corresponds to ~12 times the Lunar albedo, and may be detectable by the forthcoming Gamma Ray Large Area Space Telescope (GLAST). If detected by GLAST, it can provide unique direct information about the number of small bodies in each system that is difficult to assess by any other method. Additionally, the KBO albedo flux can be used to probe the spectrum of CR nuclei at close-to-interstellar conditions. The orbits of MBAs, Trojans, and KBOs are distributed near the ecliptic, which passes through the Galactic center and high Galactic latitudes. Therefore, the asteroid gamma-ray albedo has to be taken into account when analyzing weak gamma-ray sources close to the ecliptic, especially near the Galactic center and for signals at high Galactic latitudes, such as the extragalactic gamma-ray emission. The asteroid albedo spectrum also exhibits a 511 keV line due to secondary positrons annihilating in the rock. This may be an important and previously unrecognized celestial foreground for the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of the Galactic 511 keV line emission including the direction of the Galactic center.
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