Transient obscuration event captured in NGC 3227

II. Warm absorbers and obscuration events in archival XMM-Newton and NuSTAR observations

¹ Leiden Observatory, Leiden University, Niels Bohrweg 2, 2300 RA Leiden, The Netherlands
e-mail: Y.Wang@sron.nl
² SRON Netherlands Institute for Space Research, Niels Bohrweg 4, 2333 CA Leiden, The Netherlands
³ CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei 230026, PR China
⁴ School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, PR China
⁵ Department of Astronomy, Nanjing University, Nanjing 210093, PR China
⁶ Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, PR China
⁷ Department of Physical, Hiroshima University, 1-3-1 Kagamiyama, HigashiHiroshima, Hiroshima 739-8526, Japan
⁸ Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK
⁹ Anton Pannekoek Astronomical Institute, University of Amsterdam, PO Box 94249 1090 GE Amsterdam, The Netherlands
¹⁰ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹¹ INAF-IASF Palermo, Via U. La Malfa 153, 90146 Palermo, Italy
¹² INAF-Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, LC, Italy
¹³ MAX-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
¹⁴ Department of Physics, Technion-Israel Institute of Technology, 32000 Haifa, Israel
¹⁵ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
¹⁶ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
¹⁷ Departament de Física, EEBE, Universitat Politècnica de Catalunya, Av. Eduard Maristany 16, 08019 Barcelona, Spain
¹⁸ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹⁹ 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
²⁰ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
²¹ School of Physics and Astronomy and Wise Observatory, Tel Aviv University, Tel Aviv 69978, Israel
²² Department of Astronomy, University of Geneva, 16 Ch. d’Ecogia, 1290 Versoix, Switzerland
²³ Italian Space Agency (ASI), Via del Politecnico snc, 00133 Roma, Italy

Received: 20 June 2021
Accepted: 7 October 2021

Abstract

The relationship between warm absorber (WA) outflows of active galactic nuclei and nuclear obscuration activities caused by optically thick clouds (obscurers) crossing the line of sight is still unclear. NGC 3227 is a suitable target for studying the properties of both WAs and obscurers because it matches the following selection criteria: WAs in both ultraviolet (UV) and X-rays, suitably variable, bright in UV and X-rays, and adequate archival spectra for making comparisons with the obscured spectra. In the aim of investigating WAs and obscurers of NGC 3227 in detail, we used a broadband spectral-energy-distribution model that is built in findings of the first paper in our series together with the photoionization code of SPEX software to fit the archival observational data taken by XMM-Newton and NuSTAR in 2006 and 2016. Using unobscured observations, we find four WA components with different ionization states (log ξ [erg cm s⁻¹] ∼ −1.0, 2.0, 2.5, 3.0). The highest-ionization WA component has a much higher hydrogen column density (∼10²² cm⁻²) than the other three components (∼10²¹ cm⁻²). The outflow velocities of these WAs range from 100 to 1300 km s⁻¹, and show a positive correlation with the ionization parameter. These WA components are estimated to be distributed from the outer region of the broad line region (BLR) to the narrow line region. It is worth noting that we find an X-ray obscuration event in the beginning of the 2006 observation, which was missed by previous studies. We find that it can be explained by a single obscurer component. We also study the previously published obscuration event captured in one observation in 2016, which needs two obscurer components to fit the spectrum. A high-ionization obscurer component (log ξ ∼ 2.80; covering factor C_f ∼ 30%) only appears in the 2016 observation, which has a high column density (∼10²³ cm⁻²). A low-ionization obscurer component (log ξ ∼ 1.0 − 1.9; C_f ∼ 20%−50%) exists in both 2006 and 2016 observations, which has a lower column density (∼10²² cm⁻²). These obscurer components are estimated to reside within the BLR by their crossing time of transverse motions. The obscurers of NGC 3227 are closer to the center and have larger number densities than the WAs, which indicate that the WAs and obscurers might have different origins.