公共文化服务平台

共 7 条记录，以下是 1-7

全选清除导出

排序方式：

The connection between radio and γ-ray emission in Fermi/LAT blazars: 2012年; We collect the second Large Area Telescope AGN catalog （2LAC） and Monitor of Jets in AGN with VLBA Equipment （MOJAVE） quasi-simultaneous data to investigate the radio-γ connection of blazars. The cross sample contains 166 sources. The statistical analysis based on this sample confirms positive correlations between these two bands, but the correlations become weaker as the γ-ray energy increases. The statistical results between various parameters show negative correla- tions of γ-ray photon spectral index with γ-ray loudness for both Flat Spectrum Radio Quasars （FSRQs） and BL Lacertae objects, positive correlations of γ-ray variability index with the γ-ray loudness for FSRQs, a negative correlation of the γ-ray variabil- ity index with the γ-ray photon spectral index for FSRQs, and negative correlations of γ-ray photon spectral index with γ-ray luminosity for FSRQs. These results suggest that the γ-ray variability may be due to changes inside the γ-ray emission region like the injected power, rather than changes in the photon density of the external radiation fields, and the variability amplitude tends to be larger as the γ-rays are closer to the high energy peak of the spectral energy distribution （SED）. No correlation of variabil- ity index found for BL Lacertae objects implies that variability behavior may differ below and above the peak energy.; Xu-Liang FanJin-Ming BaiHong-Tao LiuLiang ChenNeng-Hui Liao

A puzzle of the radio-quiet quasar PG 1407+265:Are optical and X-ray emissions produced from a relativistic jet?: 2011年; PG 1407+265 is a radio quiet quasar that has a relativistic jet.In this report,we show some peculiar properties of its optical and X-ray emissions,which indicate possible non-thermal origins produced from the jet.We use a simple synchrotron + synchrotron self Compton (SSC) model to fit the emissions with different ratios of energy densities between the magnetic field and electrons (η≡U B/U e),which predicts a different γ-ray luminosity.The First LAT AGN Catalog (1LAC) did not include PG 1407+265,which indicates an upper limit of γ-ray luminosity.This upper limit constrains the ratio to be unreasonably large (η≥10 4-5).This inversely indicates that the optical and X-ray emissions may not be produced from the beaming jet.We discuss the physical implications of these results.; CHEN Liang 1,2,3 & BAI JinMing 1,2 1 National Astronomical Observatories/Yunnan Observatory,Chinese Academy of Sciences,Kunming 650011,China; 关键词：JET

平谱射电类星体在逆康普顿机制中软光子来源的研究: 2021年; 为了验证逆康普顿机制的主导过程以及主导过程中软光子的起源,通过文献收集了75个平谱射电类星体(Flat-Spectrum Radio Quasar,FSRQ)多波段的(准)同时数据,并利用对数抛物线函数拟合了频谱能量分布,分析同步峰流量与逆康普顿峰之比和多普勒因子的关系,运用自举法(Bootstrapping)计算了样本的种子因子(Seed Factor,SF)分布,用于调查软光子的起源。分析结果如下:(1)在轻子模型框架下,整个样本与子样本log[U B(νFν)EC/U ext(νFν)syn]和logδ的显著相关性表明,平谱射电类星体的高能辐射优先由外康普顿过程主导。(2)对于相对低同步峰的峰频种群,观测的种子因子分布与理论上尘埃环(Dust Torus,DT)的种子因子范围相交,表明逆康普顿过程中的软光子很可能由尘埃环主导;而对于相对高同步峰的峰频种群,观测的种子因子超过了宽线区(Broad-Line Region,BLR)或尘埃环种子因子的范围,因此无法确定软光子的来源。; 刘小鹏王泽睿杜雷鸣谢照华徐云冰邓雪娇李海凤; 关键词：活动星系核逆康普顿散射

平谱射电类星体3C 279的宽带能谱光变特性分析被引量：1: 2021年; 搜集了3C 279的29个态的光谱能量分布(Spectral Energy Distributions,SEDs)作为样本,使用稳态拐折幂律电子能谱分布(Electron Energy Distribution,EED)情况下的单区均匀轻子模型进行拟合,进而研究该源光变时外在观测与内在物理特性及它们之间的关系。主要结果如下:(1)我们的结果支持光变的激波解释(但需要斜激波)或磁重联解释。(2)外康普顿(External Compton,EC)峰的峰值光度logν^(pk)_( EC) L ^(pk) _(EC)和磁场log B之间存在一个显著的反相关关系。多普勒因子logδ和外康普顿峰的峰值光度logν^(pk) _(EC) L ^(pk) _(EC)之间存在正相关关系,意味着多普勒因子的增加是外康普顿峰的峰值光度升高的原因之一。(3)同步峰的峰值频率logν^(pk) _(syn)和峰值光度logνpk syn L pk syn之间不存在显著的正相关关系,意味着反耀变体序列不一定对所有耀变体成立。(4)参数U e/U B(相对论电子能量密度与磁场能量密度的比值)远离1,说明相对论电子与磁场之间均分趋势不明显,并且参数U e/U B中比值大于1的占86%,意味着3C 279中的喷流大多数以粒子为主导;从P B(磁场功率)
0.5表明3C 279喷流中的能量大概率也是由冷质子携带的。同时,我们发现3C 279中γ射线耗散区位于距离黑洞中心0.1~1.8 pc处,暗示着它们位于宽线区(Broad-Line Region,BLR)之外,尘埃环(Dusty Torus,DT)之内。; 孙建圆郭燕飞邓雪娇李海凤高志旭王泽睿谢照华杜雷鸣; 关键词：光度光变

蝎虎类星体Mrk 421的宽带能谱光变特性分析: 2023年; 搜集了Mrk 421的光变宽带光谱能量分布(Spectral Energy Distributions,SEDs)数据,共有73个态作为研究样本,使用电子能谱为稳态拐折幂律谱的单区轻子模型进行拟合,进而研究Mrk 421在光变时喷流的物理性质。主要结果如下:(1)样本中磁场B和多普勒因子δ之间显著反相关,说明B和δ在汤姆逊(Thomson)区相互依赖。(2)电子谱指数p_(1)支持Mrk 421光变时的激波解释或磁重联等解释。(3)同步峰值频率logν^(pk)_(syn)和峰值光度logν^(pk)_(syn)L^(pk)_(syn)之间存在正相关关系,意味着Mrk 421在光变时存在反耀变体序列。(4)根据均分参数ε=U_(e)/U_(B)(相对论电子能量密度与磁场能量密度的比值),有26%的态电子能量和磁场能量接近均分,63%的态电子能量比磁场能量大一个数量级,11%的态电子能量远大于磁场能量,这说明Mrk 421在光变过程中更可能出现电子能量比磁场能量大一个数量级的情况,同时也意味着Mrk 421中的喷流是以粒子为主导;P_(e)>P_(B)的关系进一步表明Mrk 421的喷流是以粒子为主导,P_(B)P_(r)意味着坡印廷通量不能解释辐射功率,P_(r)/P_(e)的范围为0.01~0.51,说明相对论电子能量中的一小部分可能用于观测到的辐射。(5)3C 279和Mrk 421的一些物理参数范围可能比较接近,但这两个源喷流内的物理过程可能是不一样的。; 郭燕飞孙建圆宋雨洁徐云冰谢照华杜雷鸣; 关键词：蝎虎天体光变

Possible γ-ray emission of radio intermediate AGN Ⅲ Zw 2 and its implication on the evolution of jets in AGNs被引量：1: 2010年; AGNs with hard γ-ray emission identified so far are radio-loud. Ⅲ Zw 2 is a radio intermediate AGN with a relativistic jet. We study its spectral energy distribution （SED） and find that the broad band emissions are dominated by the nonthermal emissions from the jet. We model its SED through a synchrotron ＋ inverse Compton （IC） model. The results show that the IC component of Ⅲ Zw 2 peaks at a few MeV, and the flux density drops rapidly at higher energy with photon index F 3.3 above 0.1 GeV. The predicted flux is slightly over the sensitivity of Fermi/LAT, but it was not included in the first Fermi/LAT AGN catalog. The reason for this may be： 1） that the IC peak is low and the spectrum is very steep above 0.1 GeV, 2） that Ⅲ Zw 2 is in the low state during the period of the Fermi/LAT operation. We also find that Ⅲ Zw 2 follows similar jet processes as those in γ-ray AGNs, e.g., the relation between jet power and radiation power, which is called the blazar sequence. We suggest that Ⅲ Zw 2 may be a young source at an earlier stage of jet activity.; Liang ChenJin-Ming BaiJin ZhangHong-Tao Liu; 关键词：GALAXIES NON-THERMAL

On the systematic bias in the estimation of black hole masses in active galactic nuclei被引量：1: 2014年; In this report, we find the MBH estimated from the formalism of Wang et al. are more consistent with those from the MBH-δ, relation than those from previous single-epoch mass estimators, using a large sample of AGNs. Furthermore, we examine the differences between the line widths of Hβ and Mg II in detail by comparing their line profiles. The flux around the line core and that in the wing of both Hβ and Mg II show an opposite variation tendency, which indicates the BLR is multi-componential. The contribution of the wing makes the FWHM deviate from δline, and thus bias the MBH estimated from previous single-epoch mass estimators. Thus the correction on the formalism suggested by Wang et al. is crucial to MBn estimation.; WANG JianGuoDONG XiaoBo; 关键词：QUASARS MASSES

全选清除导出

共1页<1>

国家自然科学基金(10973034)

文献类型

领域

主题

机构

作者

传媒

年份

用户反馈

国家自然科学基金(10973034)

文献类型

领域

主题

机构

作者

传媒

年份

用户登录

用户反馈