As a follow-up to the optical spectroscopic campaign aimed at achieving completeness in the Third Catalog of Hard Fermi-LAT Sources (3FHL), we present here the results of a sample of 28 blazars of an uncertain type observed using the 4 m telescope at Cerro Tololo Inter-American Observatory in Chile. Out of these 28 sources, we find that 25 are BL Lacertae objects (BL Lacs) and 3 are flat-spectrum radio quasars (FSRQs). We measure redshifts or lower limits for 16 of these blazars, and it is observed that the 12 remaining blazars have featureless optical spectra. These results are part of a more extended optical spectroscopy follow-up campaign for 3FHL blazars, where, until now, 51 blazars of an uncertain type have been classified into BL Lac and FSRQ categories. Furthermore, this campaign has resulted in redshift measurements and lower limits for 15 of these sources. Our results contribute toward attaining a complete sample of blazars above 10 GeV, which then will be crucial in extending our knowledge on blazar emission mechanisms and the extragalactic background light.

作为旨在实现第三个硬费米 LAT 源目录 (3FHL) 完整性的光学光谱活动的后续行动，我们在此展示了使用 4 m 望远镜观测到的 28 个不确定类型的耀变体样本的结果。智利托洛洛山美洲天文台。在这 28 个来源中，我们发现 25 个是 BL Lacertae 天体（BL Lacs），3 个是平谱射电类星体（FSRQ）。我们测量了其中 16 个耀变体的红移或下限，观察到剩余的 12 个耀变体具有无特征的光谱。这些结果是对 3FHL 耀变体进行更广泛的光谱后续活动的一部分，到目前为止，51 个不确定类型的耀变体已被归类为 BL Lac 和 FSRQ 类别。此外，该活动已导致其中 15 个源的红移测量和下限。我们的结果有助于获得 10 GeV 以上的完整耀变体样本，这对于扩展我们对耀变体发射机制和河外背景光的了解至关重要。