发表机构
Center for Astrophysics, Guangzhou University; Greater Bay Brand Center of the National Astronomical Data Center; Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province（广州大学天体物理中心; 国家天文数据中心大湾区品牌中心; 广东省教育厅天文科学与技术研究实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过136个FSRQs等耀变体样本，发现耀变体在α_ro−α_ox平面呈倒V形演化序列，喷流与吸积特性的差异是其双峰分布的主因，IBLs为过渡天体。
AI 中文摘要
耀变体在宽波段谱指数（α_ro−α_ox）平面上呈现出的令人困惑的双峰分布仍是一个未解决的问题。为探究其物理起源，我们编制了包含136个平谱射电类星体（FSRQs）、6个低同步峰BL Lac天体（LBLs）、39个中同步峰BL Lac天体（IBLs）和105个高同步峰BL Lac天体（HBLs）的样本。我们的结果显示，（FSRQs+LBLs）→IBLs→HBLs在α_ro−α_ox平面上遵循一个倒V形演化序列，沿该倒V形轨迹，平均5GHz射电多普勒因子、喷流功率和吸积爱丁顿比均呈下降趋势。此外，耀变体子类之间α_ox的分布仅存在微小差异，而α_ro和α_rx的分布则存在显著差异。我们的结果可通过耀变体在α_ro−α_ox平面上的分布由不同波段的吸积率和多普勒聚束效应（δ_i^q_i/δ_j^q_j）调控来自然解释，其中δ_i/δ_j在分布中起关键作用，而喷流形态（q=2(3)+α_ν）和谱指数（α_ν）的作用较小。我们的结果表明，FSRQs+LBLs是与辐射高效吸积耦合的强喷流源，其喷流从核心加速到更大距离，且在射电波段仍保持相对论速度；HBLs是与辐射低效吸积耦合的弱喷流源，其喷流可能在光学波段开始减速，传播至射电波段时呈现亚相对论速度；IBLs则被视为FSRQs+LBLs与HBLs之间的过渡天体。
英文摘要
The puzzling bimodality displayed by blazars on the broad-band spectral indices ($α_{\rm ro}-α_{\rm ox}$) plane is still an open question. To investigate its physical origin, we compiled a sample comprising 136 flat-spectrum radio quasars (FSRQs), 64 low-synchrotron-peaked BL Lac objects (LBLs), 39 intermediate-synchrotron-peaked BL Lac objects (IBLs), and 105 high-synchrotron-peaked BL Lac objects (HBLs). Our results show that (FSRQs+LBLs)$\rightarrow$IBLs$\rightarrow$HBLs follow a \reflectbox{$\angle$}-shaped evolutionary sequence on the $α_{\rm ro}-α_{\rm ox}$ plane, with the average 5\,GHz radio Doppler factor, jet power, and accretion Eddington ratio decreasing along this \reflectbox{$\angle$}-shaped track. Additionally, the distributions of $α_{\rm ox}$ exhibit only slight differences among blazar subclasses, whereas those of $α_{\rm ro}$ and $α_{\rm rx}$ differ significantly. Our results can be naturally explained if the distribution of blazars on the $α_{\rm ro}-α_{\rm ox}$ plane is regulated by the accretion rates and the Doppler beaming effect across different bands ($δ_i^{q_i}/δ_j^{q_j}$). However, $δ_i/δ_j$ plays a pivotal role in the distribution, while jet shape ($q=2(3)+α_ν$) and spectral indices ($α_ν$) play a minor role. Our results suggest that FSRQs+LBLs are strong-jet sources coupled with radiatively efficient accretion, and their jets are accelerated to a larger distance from the core and still maintain relativistic speeds down to the radio region; HBLs are weak-jet sources coupled with radiatively inefficient accretion, and their jets may begin to decelerate in the optical region and exhibit sub-relativistic speeds as they propagate to the radio region. IBLs are regarded as transitional objects between FSRQs+LBLs and HBLs.
Comments19 pages, 4 figures, and 3 tables; accepted for publication in ApJ. Comments are welcome
