Optical and X-ray discovery of the changing-look AGN IRAS23226-3843 showing extremely broad and double-peaked Balmer profiles

Abstract

We detected a very strong X-ray decline in the galaxy IRAS23226-3843 within the XMM-Newton slew survey in 2017. Subsequently, we carried out multi-band follow-up studies to investigate this fading galaxy in more detail. We took deep follow-up Swift, XMM-Newton, and NuSTAR observations in combination with optical SALT spectra of IRAS23226-3843 in 2017. In addition, we reinspected optical, UV, and X-ray data that were taken in the past. IRAS23226-3843 decreased in X-rays by a factor of more than 30 with respect to ROSAT and Swift data taken 10 to 27 years before. The broadband XMM-Newton/NuSTAR spectrum is power-law dominated, with a contribution from photoionized emission from cold gas, likely the outer accretion disk or torus. The optical continuum decreased by 60 percent and the Balmer line intensities decreased by 50 percent between 1999 and 2017. The optical Seyfert spectral type changed simultaneously with the X-ray flux from a clear broad-line Seyfert 1 type in 1999 to a Seyfert 1.9 type in 2017. The Balmer line profiles in IRAS23226-3843 are extremely broad. The profiles during the minimum state indicate that they originate in an accretion disk. The unusual flat Balmer decrement Ha/Hb with a value of 2 indicates a very high hydrogen density of n_(H) > 10 exp(11) cm^(-3) at the center of the accretion disk. IRAS23226-3843 shows unusually strong FeII blends with respect to the broad line widths, in contrast to what is known from Eigenvector 1 studies.

17 pages, 10 figures, Astronomy & Astrophysics in press. arXiv admin note: text overlap with arXiv:1804.05911

References in corpus (9)

• 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
• Broad-line Balmer Decrements in Blue Active Galactic Nuclei
• AGN Type-casting: Mrk 590 No Longer Fits the Role
• New changing look case in NGC 1566
• Spectral optical monitoring of 3C390.3 in 1995-2007: I. Light curves and flux variation of the continuum and broad lines
• Two New "Turn-off" Changing-look Active Galactic nuclei and Implication on "Partially Obscured" AGNs
• A Partial Eclipse of the Heart: The Absorbed X-ray Low State in Mrk 1048

Cited by in corpus (17)

• UGC 4211: A Confirmed Dual Active Galactic Nucleus in the Local Universe at 230 pc Nuclear Separation
• BASS XXXIX: Swift-BAT AGN with changing-look optical spectra
• Reverberation Mapping of Changing-look Active Galactic Nucleus NGC 3516
• The Eddington ratio-dependent changing look events in NGC 2992
• WISE view of changing-look AGNs: evidence for a transitional stage of AGNs
• Long-term and multi-wavelength evolution of a changing-look AGN Mrk 1018
• Investigating Changing-Look Active Galactic Nuclei with Long-term Optical and X-Ray Observations
• Active galactic nuclei ghosts: A systematic search for faded nuclei
• The outburst of the changing-look AGN IRAS23226-3843 in 2019
• Extreme Accretion Events: TDEs and Changing-Look AGN
• The Fermi-LAT view of the changing-look blazar OQ 334
• B3\,0749+460A: A New "Changing-Look" Active Galactic Nucleus Associated with X-ray Spectral Slope Variations
• XMM-Newton and NuSTAR Observations of an Optically Quiescent Quasar
• Multi-wavelength properties of changing-state active galactic nuclei: I. the evolution of soft excess and X-ray continuum
• The Great Slump: Mrk926 reveals discrete and varying Balmer line satellite components during a drastic phase of decline
• Changing Look AGN: A study of Optical/UV and the Highly Ionized Fe K$\alpha$ X-ray Line Flux Variations Using Photo-Ionization Simulations
• Low-Eddington ratio, changing-look active galactic nuclei: the case of NGC 4614