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The effects of X-ray absorption variability in NGC 4395

Authors

  • E. Nardini,

    Corresponding author
    1. Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
      E-mail: enardini@cfa.harvard.edu
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  • G. Risaliti

    1. Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
    2. INAF – Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, 50125 Firenze, Italy
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E-mail: enardini@cfa.harvard.edu

ABSTRACT

We present a new X-ray analysis of the dwarf Seyfert galaxy NGC 4395, based on two archival XMM–Newton and Suzaku observations. This source is well known for a series of remarkable properties: one of the smallest estimated black hole masses among active galactic nuclei (AGN) (of the order of ∼105 M), intense flux variability on very short time-scales (a few tens of seconds) and an unusually flat X-ray continuum (Γ∼ 1.4 over the 2–10 keV energy range). NGC 4395 is also characterized by significant variations of the X-ray spectral shape, and here we show that such behaviour can be explained through the partial occultation by circumnuclear cold absorbers with column densities of ∼1022–1023 cm−2. In this scenario, the primary X-ray emission is best reproduced by means of a power law with a standard Γ∼ 1.8 photon index, consistent with both the spectral slope observed at higher energies and the values typical of local AGN.

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