2005-2007年Blazar 3C 454.3的爆发和平静：两个可变的同步辐射峰
Blazar 3C 454.3 in Outburst and Quiescence During 2005-2007: Two Variable Synchrotron Emission Peaks
摘要：
2005年6 - 7月，我们利用斯皮策红外光谱仪（IRS：15个历元）、红外阵列相机（IRAC：12个历元）和多波段成像光度计（MIPS：2个历元）对耀变体3C454.3进行了观测。我们还从2006年12月至2007年1月的源处于低状态时，斯皮策IRS，IRAC和MIPS的意见，后者同时与一个单一的钱德拉X射线观测。此外，我们提出了光学和亚毫米监测数据。2005年至2007年期间，发生了三次重大爆发。我们提出的证据表明，无线电光学SED实际上由两个变量的同步峰，主要在红外和次级在亚毫米波长。光学爆发和亚毫米爆发之间的滞后可能表明，这两个峰值出现在沿着喷流的两个不同区域，相隔0.07-5 pc的距离。在2005年和2006年，5-35微米处的通量变化了40倍，IR峰的频率分别在最高和最低状态之间从<1 E13 Hz变化到4 E13 Hz。在中红外波段，变异性相关性良好，没有可测量的滞后。流量加倍的耀斑发生在3天的时间尺度上。当耀斑变亮时，红外SED峰向高频移动，当耀斑衰减时，红外SED峰又向低频移动。分数变化幅度随频率的增加而增加，我们认为这是由于同步加速器自吸收光学深度的减小。中红外耀斑可能是沿着预先存在的喷流或在外部介质中进入不均匀性的激波的再激发的信号。在每次大爆发期间的同步加速器峰值频率可能取决于到射流顶点的距离和冲击中的物理条件。多普勒参数沿弯曲或螺旋形喷流的变化是另一种可能性。红外同步加速器峰值的频率变化可能对解释耀变体序列产生重要影响，并且第二峰值的存在可能使人们深入了解喷流结构。
英文摘要：
We monitored the flaring blazar 3C 454.3 during 2005 June-July with the Spitzer Infrared Spectrograph (IRS: 15 epochs), Infrared Array Camera (IRAC: 12 epochs) and Multiband Imaging Photometer (MIPS: 2 epochs). We also made Spitzer IRS, IRAC, and MIPS observations from 2006 December-2007 January when the source was in a low state, the latter simultaneous with a single Chandra X-ray observation. In addition, we present optical and sub-mm monitoring data. The 2005-2007 period saw 3 major outbursts. We present evidence that the radio-optical SED actually consists of two variable synchrotron peaks, the primary at IR and the secondary at sub-mm wavelengths. The lag between the optical and sub-mm outbursts may indicate that these two peaks arise from two distinct regions along the jet separated by a distance of 0.07-5 pc. The flux at 5-35 microns varied by a factor of 40 and the IR peak varied in frequency from <1E13 Hz to 4E13 Hz between the highest and lowest states in 2005 and 2006, respectively. Variability was well correlated across the mid-IR band, with no measurable lag. Flares that doubled in flux occurred on a time scale of 3 days. The IR SED peak moved to higher frequency as a flare brightened, then returned to lower frequency as it decayed. The fractional variability amplitude increased with frequency, which we attribute to decreasing synchrotron-self absorption optical depth. Mid-IR flares may signal the re-energization of a shock that runs into inhomogeneities along the pre-existing jet or in the external medium. The synchrotron peak frequencies during each major outburst may depend upon both the distance from the jet apex and the physical conditions in the shocks. Variation of the Doppler parameter along a curved or helical jet is another possibility. Frequency variability of the IR synchrotron peak may have important consequences for the interpretation of the blazar sequence, and the presence of a secondary peak may give insight into jet structure.
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