发表机构
Shanghai Normal University; Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences（上海师范大学; 波兰科学院尼古拉·哥白尼天体物理中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过分析333个活动星系核样本，发现喷流速度与吸积模式相关，提出磁驱动喷流的洛伦兹因子由磁压与静质量能密度比决定，解释了不同类型源的喷流洛伦兹因子差异。
AI 中文摘要
在恒星级黑洞X射线双星（BHXRB）和活动星系核（AGN）中均观测到相对论性喷流，但其整体洛伦兹因子存在系统差异——黑洞X射线双星的喷流通常低于约2，而活动星系核的喷流可达到约50。这种差异的起源仍不明确。我们通过文献检索，汇编了包含333个具有精确测量喷流成分运动的活动星系核样本，其中包括270个类星体、47个BL Lac天体、10个FR I型星系和6个FR II型星系。研究发现，类星体/FR II型星系的整体洛伦兹因子范围约为1.0至41.5，平均值为11.5（中位数9.5）；相比之下，BL Lac天体/FR I型星系的Γ_jet约为1.0至21.9，平均值为4.2（中位数1.5）。这些数值，尤其是中位数，与黑洞X射线双星的结果高度相似，表明喷流速度与吸积模式之间存在强相关性。磁驱动喷流的洛伦兹因子主要由喷流底部的磁压与静质量能密度之比决定。在BL Lac天体/FR I型星系/BHXRB中，磁场由径移主导吸积流（ADAF）维持，ADAF表面的气体被磁驱动进入喷流；在类星体/FR II型星系中，磁场由吸积盘维持，而喷流底部与冕相连。我们的模型计算显示，吸积盘磁场始终远强于ADAF的磁场，因此会产生更大的Γ_jet，这可以解释两类源之间Γ_jet的系统差异。
英文摘要
Relativistic jets are observed in both stellar-mass black hole X-ray binaries (BHXRBs) and active galactic nuclei (AGNs), yet their bulk Lorentz factors differ systematically---those in black hole X-ray binaries are typically below $\sim2$, whereas AGN jets can reach $\sim50$. The origin of this discrepancy remains unclear. Searching the literature, we compile a sample of 333 AGNs with well-measured jet component motions, consisting of 270 quasars, 47 BL Lac objects, 10 FRI, and 6 FRII galaxies. We find that quasars/FRIIs exhibit minimal bulk Lorentz factors ranging from $\sim$1.0 to 41.5, with a mean of 11.5 (median 9.5). In contrast, BL Lac objects/FRIs show $Γ_{\rm jet}\sim$1.0--21.9, averaging 4.2 (median 1.5). These values, particularly the median, closely resemble those of BHXRBs, implying a strong correlation between jet speed and accretion mode. The Lorentz factor of a magnetically driven jet is mainly determined by the ratio of the magnetic pressure to rest mass energy density at the jet base. In BL Lacs/FRIs/BHXRBs, the field is maintained by the advection-dominated accretion flow (ADAF), and the gas at the ADAF surface is magnetically driven into the jets. In quasars/FRIIs, the field is maintained by the disc, while the jet base is connected to the corona. Our model calculations show that the disc field is always much stronger than that of the ADAF, and therefore leads to a larger $Γ_{\rm jet}$, which can explain the systematic difference in $Γ_{\rm jet}$ between these two types of sources.
Comments11 pages, 3 figures, accepted by MNRAS
