The estimation of γ-ray Doppler factor for Fermi/LAT-detected blazars
The estimation of γ-ray Doppler factor for Fermi/LAT-detected blazars
复制标题
DOI：
10.1017/pasa.2020.30
复制
发表时间：
2020-08
影响因子：
6.3
通讯作者：
Z. Pei;Junhui Fan;Jianghe Yang;D. Bastieri
中科院分区：
文献类型：
--
作者：
Z. Pei;Junhui Fan;Jianghe Yang;D. Bastieri
摘要blazar是活动星系核的一个子类，具有极端的观测性质，它是由相对论喷流中的束流效应引起的，该效应由多普勒因子($\δ)表示。在BLAZARS模型中，多普勒因子是一个重要的参数，用来表示所有的观测属性，人们提出了许多方法来估计它的值。本文给出了Mattox等人的一种方法。利用已有的γ射线和X射线数据，计算了809颗费米/LAT探测的X射线闪耀星的γ-射线多普勒系数下限。我们的样本包括342个平谱射电类星体(FSRQ)和467个BLLac天体(BLLac)，其中507个源是用我们之前研究的射电核心优势参数(R)汇编的。我们的计算表明，FSRQs和BLLacs的下限下限分别为$\left\langle\delta_{\gamma}|_{\textrm{FSRQ}}\right\rangle=6.87\pm4.07$和$\langedelta{\Gamma}|{\tExtrm{BL\lac}}\Right=4.31\pm2.97$。我们将我们的结果与文献中的结果进行比较和讨论。我们发现，对于某些源导出的β-γ下限比射电估算的下限要高，这可能是由于这些爆发星内的急流弯曲所致。我们的结果还表明，伽马射线区和射电区可能具有相同的相对论效应。已发现伽马射线多普勒因子与伽马射线光度和核心优势参数有关，这意味着喷流可能在伽马射线带内是连续的，而R可能是一个束流效应的指示器。
Abstract Blazars are a subclass of active galactic nuclei with extreme observation properties, which is caused by the beaming effect, expressed by a Doppler factor ( $\delta$ ), in a relativistic jet. Doppler factor is an important parameter in the blazars paradigm to indicate all of the observation properties, and many methods were proposed to estimate its value. In this paper, we present a method following Mattox et al. to calculate the lower limit on $\gamma$ -ray Doppler factor ( $\delta_{\gamma}$ ) for 809 selected Fermi/LAT-detected $\gamma$ -ray blazars by adopting the available $\gamma$ -ray and X-ray data. Our sample included 342 flat-spectrum radio quasars (FSRQs) and 467 BL Lac objects (BL Lacs), out of which 507 sources are compiled with available radio core-dominance parameter (R) from our previous study. Our calculation shows that the average values of the lower limit on $\delta_{\gamma}$ for FSRQs and BL Lacs are $\left\langle\delta_{\gamma}|_{\textrm{FSRQ}}\right\rangle = 6.87 \pm 4.07$ and $\left\langle\delta_{\gamma}|_{\textrm{BL\ Lac}}\right\rangle=4.31 \pm 2.97$ , respectively. We compare and discuss our results with those from the literature. We found that the derived lower limit on $\delta_{\gamma}$ for some sources is higher than that from the radio estimation, which could be possibly explained by the jet bending within those blazars. Our results also suggest that the $\gamma$ -ray and radio regions perhaps share the same relativistic effects. The $\gamma$ -ray Doppler factor has been found to be correlated with both the $\gamma$ -ray luminosity and core-dominance parameter, implying that the jet is possibly continuous in the $\gamma$ -ray bands, and R is perhaps an indicator for a beaming effect.