Transient obscuration event captured in NGC 3227. I. Continuum model for the broadband spectral energy distribution

Abstract

From Swift monitoring of a sample of active galactic nuclei (AGN) we found a transient X-ray obscuration event in Seyfert-1 galaxy NGC 3227, and thus triggered our joint XMM-Newton, NuSTAR, and Hubble Space Telescope (HST) observations to study this event. Here in the first paper of our series we present the broadband continuum modelling of the spectral energy distribution (SED) for NGC 3227, extending from near infrared (NIR) to hard X-rays. We use our new spectra taken with XMM-Newton, NuSTAR, and HST/COS in 2019, together with archival unobscured XMM-Newton, NuSTAR, and HST/STIS data, in order to disentangle various spectral components of NGC 3227 and recover the underlying continuum. We find the observed NIR-optical-UV continuum is explained well by an accretion disk blackbody component (Tmax = 10 eV), which is internally reddened by E(B-V) = 0.45 with a Small Magellanic Cloud (SMC) extinction law. We derive the inner radius (12 Rg) and the accretion rate (0.1 solar mass per year) of the disk by modelling the thermal disk emission. The internal reddening in NGC 3227 is most likely associated with outflows from the dusty AGN torus. In addition, an unreddened continuum component is also evident, which likely arises from scattered radiation, associated with the extended narrow-line region (NLR) of NGC 3227. The extreme ultraviolet (EUV) continuum, and the 'soft X-ray excess', can be explained with a 'warm Comptonisation' component. The hard X-rays are consistent with a power-law and a neutral reflection component. The intrinsic bolometric luminosity of the AGN in NGC 3227 is about 2.2e+43 erg/s in 2019, corresponding to 3% Eddington luminosity. Our continuum modelling of the new triggered data of NGC 3227 requires the presence of a new obscuring gas with column density NH = 5e+22 cm^-2, partially covering the X-ray source (Cf = 0.6).

Accepted for publication in Astronomy & Astrophysics (A&A), 11 pages, 7 figures

References in corpus (11)

• The AGN Black Hole Mass Database
• A fast and long-lived outflow from the supermassive black hole in NGC 5548
• The innermost region of AGN tori: implications from the HST/NICMOS Type 1 point sources and near-IR reverberation
• Broad-line Balmer Decrements in Blue Active Galactic Nuclei
• Systematic comparison of photoionised plasma codes with application to spectroscopic studies of AGN in X-rays
• Radiation spectra of warm and optically thick coronae in AGN
• A deep X-ray view of the bare AGN Ark120. IV. XMM-Newton and NuSTAR spectra dominated by two temperature (warm, hot) Comptonization processes
• Chasing obscuration in type-I AGN: discovery of an eclipsing clumpy wind at the outer broad-line region of NGC 3783
• Anatomy of the AGN in NGC 5548: II. The Spatial, Temporal and Physical Nature of the Outflow from HST/COS Observations
• Suzaku Studies of the Central Engine in the Typical Type I Seyfert NGC 3227: Detection of Multiple Primary X-ray Continua with Distinct Properties
• X-ray variability analysis of a large series of XMM-Newton + NuSTAR observations of NGC 3227

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• 10-Year Transformation of the Obscuring Wind in NGC 5548
• Multi-wavelength observations of the obscuring wind in the radio-quiet quasar MR 2251-178
• Dimming of Continuum Captured in Mrk 841: New Clues on the Nature of the Soft X-ray Excess
• Transient obscuration event captured in NGC 3227 IV. Origin of the obscuring cloud variability
• Universality of coronal properties in accreting black holes across mass and accretion rate