AGILE and Swift simultaneous observations of the blazar S50716+714 during the bright flare of October 2007
AGILE and Swift simultaneous observations of the blazar S50716+714 during the bright flare of October 2007
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DOI：
10.1051/0004-6361:200810189
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发表时间：
2008-06
影响因子：
6.5
通讯作者：
P. Giommi;S. Colafrancesco;S. Cutini;P. Marchegiani;M. Perri;C. Pittori;F. Verrecchia;A. Bulgarelli;A. Chen;F. D’Ammando;I. Donnarumma;A. Giuliani;F. Longo;L. Pacciani;G. Pucella;S. Vercellone;V. Vittorini;M. Tavani
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作者：
P. Giommi;S. Colafrancesco;S. Cutini;P. Marchegiani;M. Perri;C. Pittori;F. Verrecchia;A. Bulgarelli;A. Chen;F. D’Ammando;I. Donnarumma;A. Giuliani;F. Longo;L. Pacciani;G. Pucella;S. Vercellone;V. Vittorini;M. Tavani
我们展示了 2007 年末由 Swift 和 AGILE 卫星对 BL Lac 天体 S50716+714 进行的一系列光学、紫外线、X 射线和 γ 射线观测的结果，当时耀变体在光学频率上耀斑接近其历史最大值。我们发现，光学软 X 射线发射（可能是由于同步加速器辐射）变化很大，并且在光学 UV 和软 X 射线波段表现出不同的行为。 4-10 keV 通量很可能由逆康普顿分量主导，但保持恒定。相对较短的 AGILE GRID 观测中的计数统计数据较低，并且与 EGRET 观测到的最大值类似的恒定 γ 射线通量一致。 γ 射线光谱斜率的估计给出了接近 2 的光子指数值，表明光谱能量分布 (SED) 中逆康普顿分量的峰值位于 AGILE 能带内。在 SED 不同部分观察到的不同变化行为排除了预测高度相关通量变化的解释，例如简单 SSC 场景中波束因子或磁场的变化。观察到的 SED 变化可能会被解释为两个 SSC 分量的总和，其中一个是恒定的，而另一个是可变的，并且具有系统更高的同步加速器峰值能量。
We present the results of a series of optical, UV, X-ray and γ -ray observations of the BL Lac object S50716+714 carried out by the Swift and AGILE satellites in late 2007 when the blazar was flaring close to its historical maximum at optical frequencies. We have found that the optical through soft X-ray emission, likely due to synchrotron radiation, was highly variable and displayed a different behavior in the optical UV and soft X-ray bands. The 4-10 keV flux, most probably dominated by the inverse Compton component, instead remained constant. The counting statistics in the relatively short AGILE GRID observation was low and consistent with a constant γ -ray flux at a level similar to the maximum observed by EGRET. An estimate of the γ -ray spectral slope gives a value of the photon index that is close to 2, suggesting that the peak of the inverse Compton component in the Spectral Energy Distribution (SED) is within the AGILE energy band. The different variability behavior observed in different parts of the SED exclude interpretations predicting highly correlated flux variability like changes in the beaming factor or the magnetic field in simple SSC scenarios. The observed SED changes may instead be interpreted as due to the sum of two SSC components, one of which is constant while the other is variable and with a systematically higher synchrotron peak energy.