A changing-look Seyfert discovered by eROSITA reveals a two-component broad-line region

Markowitz A, Krumpe M, Homan D, Czerny B, Gromazdki M, Winkler H, Wilms J, Hämmerich S, Lamer G, Saha T, Buckley DA, Schramm M, Reichart DE, Salvato M, Baldini P (2026)

Publication Type: Journal article

Publication year: 2026

Journal

Astronomy & Astrophysics EDP Sciences

Book Volume: 710

Article Number: A222

DOI: 10.1051/0004-6361/202558834

Abstract

Context. Extreme sudden changes in the flow of accreting gas onto supermassive black holes manifest themselves via large-amplitude multiband continuum variability, as well as changes to broad Balmer emission profiles, driving changing-look active galactic nuclei (AGN). Aims. X-ray flux monitoring with Spectrum Roentgen Gamma (SRG)/eROSITA revealed that in the Seyfert AGN HE 1237−2252 the soft X-ray flux dipped abruptly, by a factor of 17 within 18 months. We initiated a follow-up campaign that caught the luminosity recovery after the dip, and enabled us to study how the various accretion components, including the broad-line region (BLR) and X-ray-emitting coronae, responded during this flux recovery. Methods. Our campaign included multiband photometry, X-ray spectroscopy, and optical spectroscopy. We tracked as the accretion rate relative to Eddington increased by a factor of 7 in 3 years. Results. Based on broad Hβ variability, HE 1237−2252 was subtype 1.0–1.2 in 2002, transitioned to subtype 1.8 by the time of the luminosity dip, and then transitioned back to subtype 1.0 within 3 months as luminosity recovered. Both transitions saw broad Hβ integrated line flux change by factors of 4–6. The broad Balmer profile is decomposed into a broad Gaussian consistent with virialized gas at 27 ± 3 lt-dy, plus a double-peaked profile, consistent with a diskline structure at ≳5 lt-dy. The diskline component’s relative contribution to the total profile increases as continuum flux rises. Conclusions. The lack of significant obscuration in the X-ray spectra, as well as the IR continuum dip, point to an intrinsic pause in the accretion rate as opposed to variable line-of-sight obscuration. Candidates for the underlying mechanisms include propagating cold and warm fronts in the accretion disk. The increased prominence of the diskline BLR component’s emission could be due to evolution in the physical extent of the X-ray corona, and in the fraction of > 13.6 eV photons intercepted by the diskline, as the accretion rate increases.

Authors with CRIS profile

Jörn Wilms Professur für Astronomie und Astrophysik Steven Hämmerich Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut

Involved external institutions

Nicolaus Copernicus Astronomical Centre of the Polish Academy of Sciences PL Poland (PL) Center for Theoretical Physics of the Polish Academy of Sciences PL Poland (PL) University of Warsaw / Uniwersytet Warszawski PL Poland (PL) South African Astronomical Observatory (SAAO) ZA South Africa (ZA) Leibniz Institute for Astrophysics Potsdam / Leibniz-Institut für Astrophysik Potsdam DE Germany (DE) University of Johannesburg ZA South Africa (ZA) Universität Potsdam DE Germany (DE) University of North Carolina at Chapel Hill US United States (USA) (US) Max-Planck-Institut für extraterrestrische Physik (MPE) / Max Planck Institute for Extraterrestrial Physics DE Germany (DE)

How to cite

APA:

Markowitz, A., Krumpe, M., Homan, D., Czerny, B., Gromazdki, M., Winkler, H.,... Baldini, P. (2026). A changing-look Seyfert discovered by eROSITA reveals a two-component broad-line region. Astronomy & Astrophysics, 710. https://doi.org/10.1051/0004-6361/202558834

MLA:

Markowitz, Alex, et al. "A changing-look Seyfert discovered by eROSITA reveals a two-component broad-line region." Astronomy & Astrophysics 710 (2026).

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