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arXiv 1302.6493astro-ph.HEastro-ph.EPastro-ph.IM
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分析新的INTEGRAL地球观测以测量宇宙X射线背景

Analysis of the new INTEGRAL Earth observations to measure the cosmic X-ray background

M. Türler, N. Produit, L. Pavan, C. Ferrigno, P. Bordas

摘要:

2012年开始了一系列新的地球掩星观测,以改进INTEGRAL飞行任务对宇宙X射线背景的确定。我们在这里表明,在3至160千电子伏范围内的新的探测器的光变曲线不同于在2006年获得的。而不是预期的调制引起的地球通过JEM-X,IBIS/ISGRI和SPI仪器的视野,我们记录不相关的变化在较短的时间尺度。我们讨论了2006年和2012年数据集的指向方向,航天器轨道和太阳周期相位的变化所获得的差异。我们的结论是,在2012年的地球掩星信号很可能是混合的放射性衰变时,激活的航天器穿越质子辐射带在近地点通过。另一方面,观测到的变化最有可能是由于当前的太阳活动极大期。除了来自太阳风不均匀性的可变粒子环境外,我们还发现了硬X射线极光发射的证据。前者可以通过SPI/ACS计数来追踪,后者通过不可预测地增强地球发射,是通过地球掩星测量漫射X射线背景的主要干扰。

英文摘要:

A new series of Earth occultation observations has been started in 2012 to refine the determination of the cosmic X-ray background by the INTEGRAL mission. We show here that the new detector lightcurves in the 3 to 160 keV range differ from the ones obtained in 2006. Instead of the expected modulation induced by the passage of the Earth through the field of view of the JEM-X, IBIS/ISGRI and SPI instruments, we record unrelated variability on shorter timescales. We discuss the differences obtained with the datasets of 2006 and 2012 in view of the changes in pointing direction, spacecraft orbit and solar cycle phase. We conclude that the Earth occultation signal in 2012 is likely blended by radioactive decay resulting from the activation of the spacecraft when crossing the proton radiation belt at perigee passage. The observed variability, on the other hand, results most likely from the current solar maximum. In addition to a variable particle environment from inhomogeneities of the solar wind, we also find evidence for hard X-ray auroral emission. While the former can be traced by SPI/ACS counts, the latter - by enhancing unpredictably the Earth emission - is a major disturbance for measuring the diffuse X-ray background through occultation by the Earth.

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