Blazars represent the dominant class of associated γ-ray sources detected by the Fermi Large Area Telescope (LAT). However, in the more recent release of the Fourth Fermi-LAT Point Source Catalog (4FGL), ∼25% of the sources associated with lower-energy counterparts show a multifrequency behavior similar to that of blazars, but lacks an optical spectroscopic confirmation of their nature and are therefore classified as Blazar Candidates of Uncertain Type (BCUs). A particularly challenging task in blazar studies is to classify these BCUs and, when possible to estimate their redshifts, in particular for BL Lac objects, characterized by almost featureless optical spectra with only weak emission lines. Continuing our study of blazars with Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) optical spectral data, we perform an extensive search for optical spectra available in the LAMOST Data Release 6 archive. Our aim is confirming the blazar nature of BCUs and to test if new data can allow us to get a redshift estimate for BL Lac objects that lack measurement, as well as to search for and discover changing-look blazars. We selected sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified and/or unassociated γ-ray sources, and the Roma-BZCAT multifrequency catalog of blazars, finding a total of 42 sources with available LAMOST DR6 spectra. We confirmed the blazar-like nature of four blazar candidates . For the remaining 37 sources we confirm their previous classification.

Blazars 代表相关γ的主要类别- 由费米大面积望远镜 (LAT) 探测到的射线源。然而，在最近发布的第四费米-LAT 点源目录 (4FGL) 中，约 25% 的与低能量对应源相关的源显示出类似于耀变体的多频行为，但缺乏对它们的光谱确认性质，因此被归类为不确定类型的 Blazar 候选者 (BCU)。耀变体研究中一项特别具有挑战性的任务是对这些 BCU 进行分类，并在可能的情况下估计它们的红移，特别是对于 BL Lac 天体，其特征是几乎没有特征的光谱，只有微弱的发射线。继续我们使用大天空区域多目标光纤光谱望远镜 (LAMOST) 光谱数据研究耀变体，我们对 LAMOST Data Release 6 档案中可用的光谱进行了广泛的搜索。我们的目标是确认 BCU 的耀变体性质，并测试新数据是否能让我们对缺乏测量的 BL Lac 天体进行红移估计，以及搜索和发现外观变化的耀变体。我们从 4FGL 目录中选择了来源，这是我们后续未识别和/或未关联的光谱活动的目标列表γ射线源和 Roma-BZCAT 耀变体多频目录，共发现 42 个具有可用 LAMOST DR6 光谱的源。我们确认了四个 blazar 候选者的类似 blazar 性质。对于剩余的 37 个来源，我们确认了它们之前的分类。