2007年12月至2008年1月AGILE多波长活动期间3C 273的高能变率
High energy variability of 3C 273 during the AGILE multiwavelength campaign of December 2007 - January 2008
摘要：
我们报告了在REM观测站进行的AGILE γ射线任务对平谱射电类星体3C 273进行的为期3周的多波长活动的结果，覆盖30 MeV-50 GeV和18-60 keV，（涵盖近红外和光学）、Swift（近紫外/光学，0.2-10 keV和15-50 keV）、INTEGRAL（3 - 200 keV）和Rossi XTE（2-12 keV）。这是继8年多前EGRET最后一次观测之后，包括伽马射线数据在内的第一次观测活动。我们的研究进行了同步光变曲线的源通量从所有涉及的仪器，在不同的能量范围内，在搜索相关的变化。然后，时间分辨的SED用于详细的物理模拟的排放机制。在我们行动的第二个星期，伽马射线中才发现了放射源。我们发现了一个可能的反相关性之间的排放在伽马射线和软，硬X射线，支持的全套仪器的迹象。相反，光学数据没有显示出短期的变化。只有在两次EGRET观测（1993年和1997年）中，3C 273显示出伽马射线的观测内变异。SED几乎同时的数据，部分覆盖的同步辐射，大的蓝色隆起，和逆康普顿的区域。软X射线发射与SSC和EC机制相结合是一致的，而硬X射线和伽马射线发射与来自盘的热光子的EC兼容。根据电子总数的加速事件，可以很好地解释和建模SED的时间演化，导致IC峰向更高能量移动。
英文摘要：
We report the results of a 3-weeks multi-wavelength campaign on the flat spectrum radio quasar 3C 273 carried out with the AGILE gamma-ray mission, covering the 30 MeV -50 GeV and 18-60 keV, the REM observatory (covering the near-IR and optical), Swift (near-UV/Optical, 0.2-10 keV and 15-50 keV), INTEGRAL (3 - 200 keV) and Rossi XTE (2-12 keV). This is the first observational campaign including gamma-ray data, after the last EGRET observations, more than 8 years ago. Our study was carried out using simultaneous light curves of the source flux from all the involved instruments, in the different energy ranges, in search for correlated variability. Then a time-resolved SED was used for a detailed physical modelling of the emission mechanisms. The source was detected in gamma-rays only in the second week of our campaign. We found indication of a possible anti-correlation between the emission at gamma-rays and at soft and hard X-rays, supported by the complete set of instruments. Instead, optical data do not show short term variability. Only in two EGRET observations (in 1993 and 1997) 3C 273 showed intra-observation variability in gamma-rays. The SED with almost simultaneous data, partially covers the regions of the synchrotron emission, the big blue bump, and the inverse-Compton. The soft X-ray emission is consistent with combined SSC and EC mechanisms, while hard X and gamma-ray emissions are compatible with EC from thermal photons of the disk. The time evolution of the SED is well interpreted and modelled in terms of an acceleration episode of the electrons population, leading to a shift in the IC peak towards higher energies.
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