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Extreme line profile variations in the repeating changing-look active galactic nucleus IRAS 23226-3843

  • W. Kollatschny
  • , D. Grupe
  • , H. Winkler
  • , M. A. Probst
  • , M. W. Ochmann
  • , A. Pönitzsch
  • , N. Schartel
  • , S. Wolsing
  • , S. Komossa
  • , S. B. Potter

Research output: Contribution to journalArticlepeer-review

Abstract

Aims. IRAS 23226-3843 has been identified as a highly variable Seyfert galaxy and even as a changing-look active galactic nucleus based on optical spectra. Here we present follow-up observations-taken over the past five years-for examining the ongoing photometric and spectral variations in this remarkable galaxy. Methods. We carried out Swift observations of IRAS 23226-3843 together with new optical spectra taken in 2023 and 2024. In parallel we investigate ASAS-SN photometric data from 2014 till 2025. Results. IRAS 23226-3843 stayed on a high continuum flux level in the X-ray as well as in the optical since a historic outburst in 2019. However, it shows strong short-term variations on timescales of a few months. Densely sampled ASAS-SN V-band continuum data from 2014 till 2025 confirm that behavior. IRAS 23226-3843 switched from a clear Seyfert 1 type in December 2019 to a Seyfert 1.9/2 type in July 2020 based on its optical spectra. Afterward, it again became a Seyfert 1 type with symmetric broad single-peaked Balmer line profiles in January 2023. These spectra prove the repeating changing-look character of the galaxy. IRAS 23226-3843 exhibits extreme high Balmer decrements Hα/Hβ based on their broad line components. The Balmer decrement values are on the order of 10. IRAS 23226-3843 successively showed all types of broad line Balmer profiles during the past 25 years over periods of many years: asymmetric single-peaked, double-peaked, as well as single-peaked and symmetric profiles in addition to its Seyfert 1.9/2 transition. These variations are not clearly correlated with continuum and line intensity variations.

Original languageEnglish
Article numberA46
JournalAstronomy and Astrophysics
Volume707
DOIs
Publication statusPublished - 1 Mar 2026

Keywords

  • galaxies: active
  • galaxies: individual: IRAS23226-3843
  • galaxies: nuclei
  • galaxies: Seyfert
  • quasars: emission lines
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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