The effects of X-ray absorption variability in NGC 4395

TL;DR

This paper analyzes X-ray variability in NGC 4395, attributing spectral shape changes to partial occultation by cold absorbers, and finds that the intrinsic emission aligns with typical AGN spectra.

Contribution

It demonstrates that spectral variability in NGC 4395 can be explained by partial absorption, refining understanding of its X-ray properties and intrinsic emission.

Findings

Spectral shape variations are due to cold absorber occultation.

Intrinsic X-ray emission has a standard photon index ~1.8.

Observed flux variability occurs on very short time scales.

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 (of the order of ~10^5 M_sun), intense flux variability on very short time-scales (a few tens of seconds), an unusually flat X-ray continuum (Gamma ~ 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 ~10^22-10^23 cm^-2. In this scenario, the primary X-ray emission is best reproduced by means of a power law with a standard Gamma ~ 1.8 photon index, consistent with both the spectral slope observed at higher energies and the values typical of local AGN.