AI 中文总结
利用费米大面积望远镜观测，在626个康普顿主导耀变体中搜索VHE发射源，识别出多个源并扩展了VHE FSRQ群体，研究了VHE光子与γ射线活动的时间巧合及发射区域，为多波长观测和后续天文台观测设定基准。
AI 中文摘要
在平谱射电类星体（FSRQs）的光学光谱中观测到宽发射线，表明这些天体由辐射效率高的吸积提供能量。在这类宽发射线耀变体中，强烈的宽线区（BLR）辐射可为逆康普顿散射提供种子光子，导致光谱能量分布以康普顿为主。有趣的是，同样 的BLR光子场也能吸收甚高能（VHE；E>100 GeV）γ射线辐射，这解释了检测到VHE的FSRQs为何稀少。本文报告了一项系统搜索结果，利用费米大面积望远镜约17.5年的观测，在626个康普顿主导耀变体（康普顿优势>1）样本中识别VHE发射源。我们以大于4σ的置信水平识别出14个耀变体，包括首次在VHE波段以高显著性（>5σ）检测到的4个源。我们还发现21个至少检测到一个VHE光子的天体，大幅扩展了已知的VHE FSRQ群体。通过研究VHE光子与γ射线活动的时间巧合，我们注意到在耀发以及低喷流活动时期都能检测到VHE发射。通过估计BLR光子场对γγ吸收的光学深度，我们将VHE发射区域限制在BLR之外（>1.1 - 1.4×BLR半径）。我们得出结论，对这些神秘的检测到VHE的宽线耀变体进行多波长后续观测，将使我们能够限制负责GeV - TeV发射的辐射过程，并为即将到来的切伦科夫望远镜阵列天文台的观测设定基准。
英文摘要
The observation of broad emission lines in the optical spectra of flat-spectrum radio quasars (FSRQs) suggests radiatively efficient accretion powering these objects. In such broad emission line blazars, the intense broad-line region (BLR) radiation can provide seed photons for inverse Compton scattering, leading to a Compton-dominated spectral energy distribution. Interestingly, the same BLR photon field can also absorb very high-energy (VHE; E>100 GeV) $γ$-ray radiation, thus explaining the paucity of VHE-detected FSRQs. Here we report the results of a systematic search to identify VHE-emitting sources in a sample of 626 Compton-dominated blazars (Compton dominance > 1), using $\sim$17.5 years of Fermi-Large Area Telescope observations. We identified 14 blazars at greater than 4$σ$ confidence level, including 4 sources detected in the VHE band at high significance (> 5$σ$) for the first time. We also found 21 objects from which at least one VHE photon was detected, thus substantially expanding the known VHE FSRQ population. Investigating the temporal coincidence of the VHE photons with the $γ$-ray activity, we noticed the VHE emission to be detected during flaring as well as low jet activity epochs. By estimating the optical depth for the $γ$$γ$ absorption due to the BLR photon field, we constrained the VHE-emitting region to be located outside BLR (>1.1-1.4$\times$ BLR radius). We conclude that multi-wavelength followup observations of these enigmatic VHE-detected broad line blazars will permit us to constrain the radiative processes responsible for the GeV-TeV emission, and will set the benchmark for their observations with the upcoming Cherenkov Telescope Array Observatory.
