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arXiv 1307.0907astro-ph.HEastro-ph.CO
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gamma-ray耀变体的时间序列分析及其对中心黑洞质量的影响

Time series analysis of gamma-ray blazars and implications for the central black-hole mass

Kenji Nakagawa, Masaki Mori

摘要:

耀变体活动星系核的辐射具有快速的时变特性,这通常归因于中心超大质量黑洞附近辐射区的不稳定性。活动星系核的变化时间尺度在高能区一般较快,最近由{ \it Fermi}伽玛射线空间望远镜提供的GeV能区的数据使我们能够详细研究活动星系核的时间行为。由于它在扫描模式下的宽视场,大多数天空区域每天可以观测几个小时,许多活动星系核的日光变曲线已经积累了4年多。本文通过研究15个活动星系核光变曲线在GeV能区的归一化功率谱密度,研究了它们的时变特性。一个来源,3C 454.3,显示了一个特定的时间尺度的$6.8\times10^5$ s,这个值表明,假设内部冲击模型,质量为中心黑洞的$(10^8$- $10^{10})M_\odot$这是符合其他估计。它还表明,喷射出的斑点的典型时间间隔是$(7$ - $70)$乘以史瓦西半径的光交叉时间。

英文摘要:

Radiation from the blazar class of of active galactic nuclei (AGN) exhibits fast time variability which is usually ascribed to instabilities in the emission region near the central supermassive black hole. The variability time scale is generally faster in higher energy region, and data recently provided by the {\it Fermi} Gamma-ray Space Telescope in the GeV energy band enable a detailed study of the temporal behavior of AGN. Due to its wide field-of-view in the scanning mode, most sky regions are observed for several hours per day and daily light curves of many AGN have been accumulated for more than 4 years. In this paper we investigate the time variability of 15 well-detected AGNs by studying the normalized power spectrum density (NPSD) of their light curves in the GeV energy band. One source, 3C 454.3, shows a specific time scale of $6.8\times10^5$ s, and this value suggests, assuming the internal shock model, a mass for the central black hole of $(10^8$--$10^{10})M_\odot$ which is consistent with other estimates. It also indicates the typical time interval of ejected blobs is $(7$--$70)$ times the light crossing time of the Schwarzschild radius.

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