The outburst of the changing-look AGN IRAS23226-3843 in 2019

Abstract

IRAS23226-3843 has previously been classified as a changing-look AGN based on X-ray and optical spectral variations. In 2019, Swift observations revealed a strong rebrightening in X-ray and UV fluxes in comparison to observations in 2017. We took follow-up Swift, XMM-Newton, and NuSTAR observations together with optical spectra (SALT and SAAO 1.9m telescope) from 2019 until 2021. IRAS23226-3843 showed a strong X-ray and optical outburst in 2019. It varied in the X-ray and optical continuum by a factor of 5 and 1.6, respectively, within two months. This corresponds to a factor of 3 in the optical after correction for the host galaxy contribution. The Balmer and FeII emission-line intensities showed comparable variability amplitudes. The Halpha profiles changed from a blue-peaked profile in the years 1997 and 1999 to a broad double-peaked profile in 2017 and 2019. However, there were no major profile variations in the extremely broad double-peaked profiles despite the strong intensity variations in 2019. One year after the outburst, the optical spectral type changed and became a Seyfert type 2 in 2020. Blue outflow components are present in the Balmer lines and in the Fe band in the X-rays. A deep broadband XMM-Newton/NuSTAR spectrum was taken during the maximum state in 2019. This spectrum is qualitatively very similar to a spectrum taken in 2017, but by a factor of 10 higher. The soft X-ray band appears featureless. The soft excess is well modeled with a Comptonization model. A broadband fit with a power-law continuum, Comptonized soft excess, and Galactic absorption gives a good fit to the combined EPIC-pn and NuSTAR spectrum. In addition, we see a complex and broadened Fe K emission-line profile in the X-rays. The changing-look character in IRAS23226-3843 is most probably caused by changes in the accretion rate -- based on the short-term variations on timescales of weeks to months.

21 pages, 14 figures, Astronomy & Astrophysics in press

References in corpus (21)

• HI4PI: A full-sky HI survey based on EBHIS and GASS
• Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
• The Discovery of the First "Changing Look" Quasar: New Insights into the Physics & Phenomenology of AGN
• The diversity of quasars unified by accretion and orientation
• Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548
• Black hole feedback in the luminous quasar PDS 456
• AGN Type-casting: Mrk 590 No Longer Fits the Role
• The destruction and recreation of the X-ray corona in a changing-look Active Galactic Nucleus
• The Close AGN Reference Survey (CARS) - Mrk 1018 returns to the shadows after 30 years as a Seyfert 1
• Multi-dimensional modelling of X-ray spectra for AGN accretion-disk outflows
• New changing look case in NGC 1566
• The Close AGN Reference Survey (CARS) - What is causing Mrk1018's return to the shadows after 30 years?
• Spectral optical monitoring of 3C390.3 in 1995-2007: I. Light curves and flux variation of the continuum and broad lines
• Magnetic flux inversion in a peculiar changing look AGN
• Changing-look event in NGC 3516: continuum or obscuration variability?
• Long-term and multi-wavelength evolution of a changing-look AGN Mrk 1018
• Evolution of the accretion disk around the supermassive black hole of NGC 7213
• The X-ray Disk/Wind Degeneracy in AGN
• Optical and X-ray discovery of the changing-look AGN IRAS23226-3843 showing extremely broad and double-peaked Balmer profiles
• A New Emulated Monte Carlo Radiative Transfer Disk-Wind Model: X-Ray Accretion Disk-wind Emulator -- XRADE
• A radio, optical, UV and X-ray view of the enigmatic changing look Active Galactic Nucleus 1ES~1927+654 from its pre- to post-flare states

Cited by in corpus (6)

• Investigating Changing-Look Active Galactic Nuclei with Long-term Optical and X-Ray Observations
• The transient event in NGC 1566 from 2017 to 2019 -- I. An eccentric accretion disk and a turbulent, disk-dominated broad-line region unveiled by double-peaked Ca II and O I lines
• Long-term optical spectral monitoring of a changing-look active galactic nucleus NGC 3516 -- II. Broad-line profile variability
• Still alive and kicking: A significant outburst in changing-look AGN Mrk 1018
• Multi-wavelength properties of changing-state active galactic nuclei: I. the evolution of soft excess and X-ray continuum
• Flares in the Changing Look AGN Mrk 590. II: Deep X-ray observations reveal a Comptonizing inner accretion flow