galaxies: active; galaxies: Seyfert; X-rays: galaxies; Active galactic nuclei; Galaxies active; Galaxy:seyfert; Multi-wavelength study; Multiwavelength; Optical spectrum; Seyferts; Spectra's; Supermassive black holes; X-rays: Galaxies; Astronomy and Astrophysics; Space and Planetary Science
Abstract :
[en] Context. Multiwavelength studies of transients in actively accreting supermassive black holes have revealed that large-amplitude variability is frequently linked to significant changes in the optical spectra. This phenomenon is known as a changing-look active galactic nucleus (CLAGN). Aims. In 2020, the Zwicky Transient Facility detected a transient flaring event in the type 1.9 AGN LEDA 1154204, wherein the brightness sharply increased by 0.55 mag in one month and then began to decay. Spectrum Roentgen Gamma (SRG)/eROSITA also observed the object as part of its all-sky X-ray surveys after the flare had started to decay. Methods. We performed a three-year multiwavelength follow-up campaign to track the spectral and temporal characteristics of the source during the post-flare fading. This campaign included optical spectroscopy, X-ray spectroscopy and photometry, and ultraviolet, optical, and infrared continuum photometry. Results. Optical spectra taken near the flare peak revealed a broad double-peaked Hβ emission and a blue continuum, neither of which were detected in a 2005 archival spectrum. The broad Hβ had increased by a factor of > 5–6. From late 2020 through 2023, the broad Balmer-line flux faded as the continuum faded, and the Balmer decrement increased by ∼2.2. This is consistent with the expected ionization response. The X-ray spectrum exhibits no significant spectral variability despite dramatic flux variation of a factor of 17. There is no evidence of a soft X-ray excess, which indicates an energetically unimportant warm corona. Conclusions. The transient event was likely triggered by a disk instability in a preexisting AGN-like accretion flow that culminated in the observed multiwavelength variability (X-rays via thermal Comptonization, illumination of the broad-line region, and infrared dust echo) and in the CLAGN event.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Saha, T. ; Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, Warszawa, Poland ; Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany
Markowitz, A. ; Nicolaus Copernicus Astronomical Center of the Polish Academy of Sciences, Warszawa, Poland ; Center for Astrophysics and Space Sciences, University of California, San Diego, United States
Homan, D.; Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany
Krumpe, M.; Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany
Haemmerich, S.; Dr. Karl Remeis-Observatory, ECAP, Friedrich-Alexander-Universität Erlangen-Nürnberg, Bamberg, Germany
Czerny, B.; Center for Theoretical Physics, Polish Academy of Sciences, Warszawa, Poland
Graham, M. ; Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, United States
Frederick, S. ; Department of Astronomy, University of Maryland, College Park, United States ; Department of Astronomy, Vanderbilt University, Nashville, United States
Gromadzki, M. ; Astronomical Observatory, University of Warsaw, Warszawa, Poland
Gezari, S.; Space Telescope Science Institute, Baltimore, United States
Winkler, H. ; Department of Physics, University of Johannesburg, Johannesburg, South Africa
Buckley, D.A.H. ; South African Astronomical Observatory, Cape Town, South Africa ; Department of Astronomy, University of Cape Town, Rondebosch, South Africa ; Department of Physics, University of the Free State, Bloemfontein, South Africa
Brink, J. ; Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany ; South African Astronomical Observatory, Cape Town, South Africa ; Department of Astronomy, University of Cape Town, Rondebosch, South Africa
Naddaf Moghaddam, Mohammad Hassan ; Université de Liège - ULiège > Unités de recherche interfacultaires > Space sciences, Technologies and Astrophysics Research (STAR)
Rau, A.; Max Planck Institute for Extraterrestrial Physics, Garching, Germany
Wilms, J.; Dr. Karl Remeis-Observatory, ECAP, Friedrich-Alexander-Universität Erlangen-Nürnberg, Bamberg, Germany
Gokus, A.; Dr. Karl Remeis-Observatory, ECAP, Friedrich-Alexander-Universität Erlangen-Nürnberg, Bamberg, Germany ; Department of Physics, McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, United States ; Lehrstuhl für Astronomie, Universität Würzburg, Würzburg, Germany
Liu, Z.; Max Planck Institute for Extraterrestrial Physics, Garching, Germany
Grotova, I.; Max Planck Institute for Extraterrestrial Physics, Garching, Germany
The authors thank the anonymous referee for the comments and suggestions. The authors acknowledge insightful discussions with Prof. Chris Done, Prof. Ji\u02C7r\u00ED Svoboda, and Prof. Piotr \u02D9Zycki. TS acknowledges full and partial support from Polish Narodowym Centrum Nauki grants 2018/31/G/ST9/03224 and 2016/23/B/ST9/03123, and partial supportfrom Deutsches Zentrum f\u00FCr Luft- und Raumfahrt (DLR) grant FKZ 50 OR 2004. AM acknowledges full or partial support from Polish Narodowym Centrum Nauki grants 2016/23/B/ST9/03123, 2018/31/G/ST9/03224, and 2019/35/B/ST9/03944. DH acknowledges support from DLR grant FKZ 50 OR 2003. MK is supported DLR grant FKZ 50 OR 2307. MG is supported by the EU Horizon 2020 research and innovation programme under grant agreement No 101004719. SH is supported by the German Science Foundation (DFG grant number WI 1860/14-1). DAHB & JB acknowledge support from the National Research Foundation. This work is based on data from eROSITA, the soft X-ray instrument aboard SRG, a joint Russian-German science mission supported by the Russian Space Agency (Roskosmos), in the interests of the Russian Academy of Sciences represented by its Space Research Institute (IKI), and the Deutsches Zentrum f\u00FCr Luft- und Raumfahrt (DLR). The SRG spacecraft was built by Lavochkin Association (NPOL) and its subcontractors, and is operated by NPOL with support from the Max Planck Institute for Extraterrestrial Physics (MPE). The development and construction of the eROSITA X-ray instrument was led by MPE, with contributions from the Dr. Karl Remeis Observatory Bamberg & ECAP (FAU Erlangen-Nuernberg), the University of Hamburg Observatory, the Leibniz Institute for Astrophysics Potsdam (AIP), and the Institute for Astronomy and Astrophysics of the University of T\u00FCbingen, with the support of DLR and the Max Planck Society. The Argelander Institute for Astronomy of the University of Bonn and the Ludwig Maximilians Universit\u00E4t Munich also participated in the science preparation for eROSITA. The eROSITA data shown here were processed using the eSASS software system developed by the German eROSITA consortium. This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. This research has made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC. This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. The ATLAS project is primarily funded to search for near earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen\u2019s University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory, and The Millennium Institute of Astrophysics (MAS), Chile. Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm Uni versity, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Lab- oratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Berkeley National Laboratories, Lawrence Livermore National Laboratories, and IN2P3, France. Operations areconducted by COO, IPAC, and UW. This paper uses observations made from the South African Astronomical Observatory (SAAO). Some of the observations reported in this paper were obtained with the Southern African LargeTelescope (SALT) under programs 2020-2-MLT-008 (PI: A. Markowitz) and 2021-2-LSP-001 (PI: D. Buckley). Polish participation in SALT is funded by grant No. MEiN nr 2021/WK/01. The paper is based on observations collectedat the European Southern Observatory under ESO programme 109.23MH.001. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, LosAngeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This publica- tion also makes use of data products from NEOWISE, which is a project ohe Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Extragalactic Database(NED), which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology. We made extensive use of the following open-sourceThe authors thank the anonymous referee for the comments and suggestions. The authors acknowledge insightful discussions with Prof. Chris Done, Prof. Ji\u0159\u00ED Svoboda, and Prof. Piotr \u017Bycki. TS acknowledges full and partial support from Polish Narodowym Centrum Nauki grants 2018/31/G/ST9/03224 and 2016/23/B/ST9/03123, and partial support from Deutsches Zentrum f\u00FCr Luft- und Raumfahrt (DLR) grant FKZ 50 OR 2004. AM acknowledges full or partial support from Polish Narodowym Centrum Nauki grants 2016/23/B/ST9/03123, 2018/31/G/ST9/03224, and 2019/35/B/ST9/03944. DH acknowledges support from DLR grant FKZ 50 OR 2003. MK is supported DLR grant FKZ 50 OR 2307. MG is supported by the EU Horizon 2020 research and innovation programme under grant agreement No 101004719. SH is supported by the German Science Foundation (DFG grant number WI 1860/14-1). DAHB & JB acknowledge support from the National Research Foundation. This work is based on data from eROSITA, the soft X-ray instrument aboard SRG, a joint Russian-German science mission supported by the Russian Space Agency (Roskosmos), in the interests of the Russian Academy of Sciences represented by its Space Research Institute (IKI), and the Deutsches Zentrum f\u00FCr Luft- und Raumfahrt (DLR). The SRG spacecraft was built by Lavochkin Association (NPOL) and its subcontractors, and is operated by NPOL with support from the Max Planck Institute for Extraterrestrial Physics (MPE). The development and construction of the eROSITA X-ray instrument was led by MPE, with contributions from the Dr. Karl Remeis Observatory Bamberg & ECAP (FAU Erlangen-Nuernberg), the University of Hamburg Observatory, the Leibniz Institute for Astrophysics Potsdam (AIP), and the Institute for Astronomy and Astrophysics of the University of T\u00FCbingen, with the support of DLR and the Max Planck Society. The Argelander Institute for Astronomy of the University of Bonn and the Ludwig Maximilians Universit\u00E4t Munich also participated in the science preparation for eROSITA. The eROSITA data shown here were processed using the eSASS software system developed by the German eROSITA consortium. This work is based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. This research has made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC. This work has made use of data from the Asteroid Terrestrial-impact Last Alert System (ATLAS) project. The ATLAS project is primarily funded to search for near earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, the Queen\u2019s University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory, and The Millennium Institute of Astrophysics (MAS), Chile. Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Berkeley National Laboratories, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW. This paper uses observations made from the South African Astronomical Observatory (SAAO). Some of the observations reported in this paper were obtained with the Southern African Large Telescope (SALT) under programs 2020-2-MLT-008 (PI: A. Markowitz) and 2021-2-LSP-001 (PI: D. Buckley). Polish participation in SALT is funded by grant No. MEiN nr 2021/WK/01. The paper is based on observations collected at the European Southern Observatory under ESO programme 109.23MH.001. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This publication also makes use of data products from NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology, funded by the Planetary Science Division of the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology. We made extensive use of the following open-source python packages: NumPy (Harris et al. 2020), Matplotlib (Hunter 2007), SciPy (Virtanen et al. 2020), and Astropy (Astropy Collaboration 2022).
