An X-ray and optical spectral study of the changing-look narrow-line Seyfert 1 2MASX J0413-0050

¹ Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
² INAF – Astronomical Observatory of Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
³ European Southern Observatory, Alonso de Córdova 3107, Casilla 19 Santiago 19001, Chile
⁴ INAF – Astrophysics and Space Science Observatory of Bologna, Via Gobetti, 93/3, 40129 Bologna, Italy
⁵ University of Belgrade – Faculty of Mathematics, Department of astronomy, Studentski trg 16, 11000 Belgrade, Serbia
⁶ Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
⁷ Department of Physics & Astronomy, Texas Tech University, Box 41051 Lubbock, TX 79409-1051, USA
⁸ Department of Astronomy, University of Geneva, ch. d’Ecogia 16, 1290 Versoix, Switzerland
⁹ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Avenida Ejercito Libertador 441, Santiago, Chile
¹⁰ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
¹¹ Osservatorio Astronomico di Brera, Istituto Nazionale di Astrofisica (INAF), Via Emilio Bianchi, 46, 23807 Merate, Italy
¹² Dipartimento di Scienza e Alta Tecnologia, Università dell’Insubria, Via Valleggio 11, 22100 Como, Italy
¹³ Physics Department, Technion, Haifa 32000, Israel
¹⁴ Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica, 1 Roma 00133, Italy
¹⁵ Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
¹⁶ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, FI-02540 Kylmälä, Finland
¹⁷ Aalto University Department of Electronics and Nanoengineering, P.O. Box 15500, FI-00076 AALTO, Finland

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Received: 16 February 2026
Accepted: 6 May 2026

Abstract

Active galactic nuclei (AGN) showing dramatic spectral and flux variations, either due to changes in the accretion rate (‘changing-state’ CS-AGN) of the supermassive black hole or in the line-of-sight column density (‘changing-obscuration’ CO-AGN), have been classified as changing-look AGN (CL-AGN). Here we present a peculiar source, 2MASX J0413-0050, first identified as a narrow-line Seyfert 1 (NLS1s) galaxy in 2004. When re-observed twice in 2021, it showed a transition in the spectral type (towards a Seyfert 1.9) and the complete and mysterious disappearance of the Hβ line while the source was in a high-accretion state. In the meantime, the X-ray flux decreased between observations taken in 2020 and 2022, and again in the most recent spectrum of 2023. Shortly after this, another optical spectrum revealed the re-emergence of both the narrow and broad Hβ components (Seyfert 1.8). Despite the fact that it was not possible to retrieve the line-of-sight column density from the X-ray spectra, which would have helped in assessing whether this event could be attributed to a CO-AGN scenario, the observational evidence does not necessarily support such an interpretation. J0413-0050 may have undergone several switch-on and switch-off phases over the past 20 years, on an unknown timescale, which could have affected the accretion power and, consequently, the optical continuum and so the emission lines coming from the broad-line region (BLR). For these reasons, it is reasonable to classify this source as a CS-AGN. The case of J0413-0050 supports the hypothesis that NLS1s can indeed experience CL phenomena.