On the origin of the soft photons of the high synchrotron peaked blazar : PKS 1424+240
On the origin of the soft photons of the high synchrotron peaked blazar : PKS 1424+240
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DOI：
10.1093/mnras/stw1312
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发表时间：
2016-06
影响因子：
4.8
通讯作者：
Shi-Ju Kang;Yonggang Zheng;Qingwen Wu;L. Chen
中科院分区：
文献类型：
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作者：
Shi-Ju Kang;Yonggang Zheng;Qingwen Wu;L. Chen
PKS 1424+240是一个遥远的极高能γ射线BL Lac天体，红移z=0.601$。发现纯同步自康普顿（SSC）过程通常需要极端的输入参数（例如，非常低的磁场强度和非常大的多普勒因子）来解释其多波长光谱能量分布（SED）。为了避免极端的模型参数，已经提出了不同的模型（例如，两带SSC模型或轻强子模型）。在这项工作中，我们采用传统的单区轻子模型，包括一个弱的外部康普顿分量，重新探索PKS 1424+240在高（2009）和低（2013）状态下的同时多波长SED。我们发现，无论是来自宽线区（BLR）还是尘埃环的弱外光子场，其输入磁场参数和多普勒因子与其它BL拉克的输入磁场参数和多普勒因子基本一致。然而，来自BLR或环面的种子光子所需的能量密度比发光类星体中所限制的能量密度小约3个数量级（例如，平谱射电类星体（Flat spectrum radio quasars，FSRQs）。这一结果表明，BL拉克中的BLR/torus比FSRQs中的BLR/torus弱得多（但不是完全消失），即使在高同步辐射峰值的耀变体中，来自BLR/torus的外光子的逆康普顿效应仍可能起作用。
PKS 1424+240 is a distant very high energy gamma-ray BL Lac object with redshift $z=0.601$. It was found that pure synchrotron self-Compton (SSC) process normally need extreme input parameters (e.g., very low magnetic field intensity and extraordinarily large Doppler factor) to explain its multi-wavelength spectral energy distributions (SEDs). To avoid the extreme model parameters, different models have been proposed (e.g., two-zone SSC model or lepto-hadronic model). In this work, we employ the traditional one-zone leptonic model after including a weak external Compton component to re-explore the simultaneous multi-wavelength SEDs of PKS 1424+240 in both high (2009) and low (2013) states. We find that the input parameters of magnetic field and Doppler factor are roughly consistent with those of other BL Lacs if a weak external photon field from either broad line region (BLR) or the dust torus. However, the required energy density of seed photons from BLR or torus is about 3 orders of magnitude less than that constrained in luminous quasars (e.g., flat-spectrum radio quasars, FSRQs). This result suggests that the BLR/torus in BL Lacs is much weaker than that of luminous FSRQs (but not fully disappear), and the inverse-Compton of external photons from BLR/torus may still play a role even in high synchrotron peaked blazars.