Transient obscuration event captured in NGC 3227
Astronomy and Astrophysics, vol. 665, pp. A72
Abstract
Context. A growing number of transient X-ray obscuration events in type I active galactic nuclei suggest that our line of sight to the central engine is not always free. Multiple X-ray obscuration events were reported in the nearby Seyfert 1.5 galaxy NGC 3227 from 2000 to 2016. In late 2019, another X-ray obscuration event was identified with Swift. Two coordinated target-of-opportunity observations with XMM-Newton, NuSTAR, and the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) were triggered in November and December 2019 to study this obscuration event. Aims. We aim to constrain the physical properties of the absorbing material (i.e., the obscurer) that caused the X-ray obscuration event in late 2019. We also aim to compare the handful of obscuration events in NGC 3227 and other Seyfert galaxies. Methods. For each observation, we analyzed the time-averaged X-ray spectra collected with XMM-Newton and NuSTAR. We performed photoionization modeling with the SPEX code, which allows us to constrain the intrinsic continuum simultaneously with various photoionized absorption and emission components. Results. Similar to previous transient X-ray obscuration events in NGC 3227, the one caught in late 2019 is short-lived (less than five months). If the obscurer has only one photoionized component, the two X-ray observations in late 2019 cannot be explained by the same obscurer that responds to the varying ionizing continuum. Due to the unknown geometry of the obscurer, its number density and distance to the black hole cannot be well constrained. The inferred distance covers at least two orders of magnitude, from the broad-line region to the dusty torus. Unlike some other X-ray obscuration events in Seyfert galaxies, such as NGC 5548 and NGC 3783, no prominent blueshifted, broad absorption troughs were found in the 2019 HST/COS spectra of NGC 3227 when compared with archival UV spectra. This might be explained if the X-ray obscurer does not intercept our line of sight to (a significant portion of) the UV-emitting region. Understanding the variety of observational differences in the X-ray obscuration events observed so far is not straightforward. Future observations with high-quality data are needed to unveil the nature of the X-ray obscuration events.
Authors 19
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Hiroshima University · Space Research Organisation Netherlands
Affiliation as printed
Department of physics, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
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Leiden University · Leiden Observatory · Space Research Organisation Netherlands
Affiliation as printed
Leiden Observatory, Leiden University, PO Box 9513 2300 Leiden, The Netherlands
SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
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Space Telescope Science Institute
Affiliation as printed
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
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Space Telescope Science Institute
Affiliation as printed
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
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Leiden University · University of Science and Technology of China · Chinese Academy of Sciences · Leiden Observatory · Space Research Organisation Netherlands · Nanjing University
Affiliation as printed
CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China
Department of Astronomy, Nanjing University, Nanjing 210093, PR China
Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, PR China
Leiden Observatory, Leiden University, PO Box 9513 2300 Leiden, The Netherlands
SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, PR China
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Affiliation as printed
Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
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Affiliation as printed
Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
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National Institute for Astrophysics
Affiliation as printed
INAF-IASF Palermo, Via U. La Malfa 153, 90146 Palermo, Italy
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Affiliation as printed
Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
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Affiliation as printed
Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
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Affiliation as printed
Italian Space Agency (ASI), Via del Politecnico snc, 00133 Roma, Italy
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Affiliation as printed
Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy
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Centre National de la Recherche Scientifique · Institut de Planétologie et d'Astrophysique de Grenoble · Université Grenoble Alpes
Affiliation as printed
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
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Universitat Politècnica de Catalunya
Affiliation as printed
Departament de Física, EEBE, Universitat Politècnica de Catalunya, Av. Eduard Maristany 16, 08019 Barcelona, Spain
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Brera Astronomical Observatory · Max Planck Institute for Extraterrestrial Physics
Affiliation as printed
INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy
Max Planck Institute fur Extraterrestriche Physik, 85748 Garching, Germany
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Affiliation as printed
Department of physics, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan
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European Space Agency · European Space Astronomy Centre
Affiliation as printed
Telespazio UK for the European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo, s/n, 28692 Villanueva de la Cañada, Madrid, Spain
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Technion – Israel Institute of Technology
Affiliation as printed
Department of Physics, Technion-Israel Institute of Technology, 32000 Haifa, Israel
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