Probing the jets of blazars using the temporal symmetry of their multiwavelength outbursts
Probing the jets of blazars using the temporal symmetry of their multiwavelength outbursts
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利用多波长爆发的时间对称性探测耀变体喷流
DOI：
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发表时间：
2018
影响因子：
4.8
通讯作者：
Aritra Ghosh
中科院分区：
文献类型：
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作者：
N. Roy;R. Chatterjee;M. Joshi;Aritra Ghosh
我们使用费米-LAT和耶鲁/SMARTS监测项目的光曲线，比较了10个blazar样本中$sim$200长期($sim$数周-月)GeV和R波段爆发以及$sim$25短期($sim$hr-day)GeV耀斑的升降时间。我们发现，大多数长期爆发是对称的，这表明观测到的变率是由扰动(如激波)的交叉时间尺度所主导的。较大比例的短期耀斑是不对称的，与上升时间尺度相比，衰减时间更长和更短的比例大致相同。我们使用多区辐射反馈(MUZORF)模型来解释上述结果。我们发现，缓慢上升时间的爆发表明粒子逐渐加速到GeV能量。改变等离子体的整体洛伦兹因子或激波区的宽度可以导致冷却时间的增加，从而导致比衰变时间更快的上升。如果考虑单一发射机制，例如BLR光子的外部康普顿散射，则诸如宽线区域(BLR)的光度或距离等参数对冷却时间影响很大，但如果包括其他机制，例如，同步加速器自康普顿和环面光子的外部康普顿散射，则不会影响冷却时间。这项工作对耀斑的对称性进行了系统的研究，可用于在MUZORF模型的背景下估计blazar喷流的相关几何和物理参数。
We compare the rise and decay timescales of $sim$200 long-term ($sim$weeks-months) GeV and R-band outbursts and $sim$25 short-term ($sim$hr-day) GeV flares in a sample of 10 blazars using light curves from the Fermi-LAT and the Yale/SMARTS monitoring project. We find that most of the long-term outbursts are symmetric, indicating that the observed variability is dominated by the crossing timescale of a disturbance, e.g., a shock. A larger fraction of short-term flares are asymmetric with an approximately equal fraction of longer and shorter decay than rise timescale. We employ the MUlti-ZOne Radiation Feedback (MUZORF) model to interpret the above results. We find that the outbursts with slow rise times indicate a gradual acceleration of the particles to GeV energy. A change in the bulk Lorentz factor of the plasma or the width of the shocked region can lead to an increase of the cooling time causing a faster rise than decay time. Parameters such as the luminosity or the distance of the broad line region (BLR) affects the cooling time strongly if a single emission mechanism, e.g., external Compton scattering of BLR photons is considered but may not if other mechanisms, e.g., synchrotron self-compton and external Compton scattering of the torus photon are included. This work carries out a systematic study of the symmetry of flares, which can be used to estimate relevant geometric and physical parameters of blazar jets in the context of the MUZORF model.