Journal Article

The effects of X-ray absorption variability in NGC 4395

E. Nardini and G. Risaliti

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 417, issue 4, pages 2571-2576
Published in print November 2011 | ISSN: 0035-8711
Published online November 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19423.x
The effects of X-ray absorption variability in NGC 4395

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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.

Keywords: galaxies: active; galaxies: individual: NGC 4395; X-rays: galaxies

Journal Article.  4865 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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