Revised optical classification of a sample of gamma-ray-emitting active galactic nuclei with GTC and VLT

¹ Universitá degli studi dell’Insubria Via Valleggio 11 Como 22100, Italy
² Osservatorio Astronomico di Brera, Istituto Nazionale di Astrofisica (INAF) Via E. Bianchi 46 Merate (LC) 23807, Italy
³ European Southern Observatory (ESO) Alonso de Córdova 3107 Vitacura Santiago, Chile
⁴ Department of Physics and Astronomy, Texas Tech University Box 41051 Lubbock 79409-1051 TX, USA
⁵ Osservatorio Astronomico di Padova, Istituto Nazionale di Astrofisica (INAF) Vicolo dell’Osservatorio 5 35122 Padova, Italy
⁶ Dipartimento di Fisica e Astronomia “G. Galilei”, Università degli studi di Padova Vicolo dell’Osservatorio 3 Padova 35122, Italy
⁷ Jeremiah Horrocks Institute, University of Central Lancashire Preston PR1 2HE, UK
⁸ Osservatorio Astronomico di Cagliari, Istituto Nazionale di Astrofisica (INAF) Via della Scienza 5 09047 Selargius, Italy
⁹ CFisUC, Departamento de Física, Universidade de Coimbra 3004-516 Coimbra, Portugal
¹⁰ Dept. of Physics & Astronomy and Dept. of Computer Science, University College London Gower Street London WC1E 6BT, UK
¹¹ Dipartimento di Fisica, Università di Roma Tor Vergata Via della Ricerca Scientifica 1 00133 Roma, Italy
¹² Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales Avenida Ejercito Libertador 441 Santiago, Chile

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Received: 10 September 2025
Accepted: 15 November 2025

Abstract

We report the results of the optical follow-up of a sample of γ-ray-emitting active galactic nuclei (AGNs). New high-quality optical spectra were obtained using the Gran Telescopio Canarias with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy and the European Southern Observatory’s Very Large Telescope Unit Telescope 1 with the FOcal Reducer and low dispersion Spectrograph 2. From the analysis of these spectra, we confirmed the previous narrow-line Seyfert 1 (NLS1) classification for four objects and discovered two new NLS1s, bringing the total number of optically confirmed γ-NLS1s to 26. We also identified two ambiguous cases between NLS1 and intermediate Seyfert (IS), three ISs, one broad-line Seyfert 1, and one Seyfert 2. Based on the new spectra, we calculated black hole masses ranging from 10^6.25 to 10^9.32 M_⊙ and Eddington ratios spanning 0.05 to 2.07. This reclassification provides support for the scenario in which AGNs with relatively low black hole masses are capable of launching powerful relativistic jets and contributes to our broader understanding of γ-ray-emitting AGNs.