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

A. Vietri, A. Tortosa, D. Ilić, S. Ciroi, M. Berton, E. Järvelä, C. Ricci, E. Sani, L. Crepaldi, B. Dalla Barba, S. Chen, E. Congiu, P. Condò, I. Varglund, G. Rodighiero

First listed 2026-05-06 | Last updated 2026-05-06

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 (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 Hbeta line while 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 Hbeta 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 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.

Short digest

This paper tracks the changing-look behavior of the narrow-line Seyfert 1 2MASX J0413-0050 across optical spectroscopy and X-ray observations spanning roughly 2004 to 2023. The key result is an unusual optical transition in 2021: the source moved toward a Seyfert 1.9 state with the complete disappearance of Hbeta even while remaining in a high-accretion regime, followed later by the re-emergence of both narrow and broad Hbeta in a Seyfert 1.8 phase. Over the same period, the X-ray flux declined from 2020 to 2022 and again in 2023, but the line-of-sight column density could not be constrained well enough to support a changing-obscuration explanation. The authors therefore argue that repeated switch-on/switch-off episodes in the accretion flow are the more plausible driver, making J0413-0050 a strong case that NLS1s can undergo genuine changing-state phenomena.

Key figures to inspect

• Inspect the multi-epoch optical spectra that cover Hbeta and Halpha to see the core changing-look evidence directly: the 2004 NLS1 classification, the 2021 disappearance of Hbeta, and the later re-emergence of broad and narrow Hbeta that shifts the source back to a Seyfert 1.8 state.
• Look for any zoomed line-profile decomposition around the Balmer region, especially fits separating broad and narrow components plus Fe II if modeled; this should clarify whether the classification change is driven by genuine BLR fading rather than only continuum-placement or blending effects.
• Find the X-ray spectral comparison across the 2020, 2022, and 2023 observations to check how the flux decline appears in practice and whether the spectra show strong absorption signatures, spectral-shape changes, or instead mainly luminosity evolution.
• Prioritize any long-term timeline or summary figure combining optical type, Balmer-line visibility, and X-ray brightness versus observing date; that figure should be the fastest way to assess the proposed switch-on/switch-off history over the last two decades.
• If present, inspect a diagnostic plot comparing accretion-state indicators with optical spectral type, since the paper’s most intriguing claim is that Hbeta vanished during a high-accretion phase rather than in an obvious low-state turn-off event.