Work

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

Year: 2026

Type: article

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 H α /H β 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.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202558093