The Multi-Layer Variable Absorbers in NGC 1365 Revealed by XMM-Newton and NuSTAR

TL;DR

This study uses XMM-Newton and NuSTAR observations to reveal complex, multi-layer variable absorption in NGC 1365, including neutral, ionized, and Compton-thick components, shedding light on the geometry of the absorbing material.

Contribution

It provides the first detailed characterization of multi-layer variable absorbers in NGC 1365, including the identification of three distinct neutral absorption zones and their relation to source flux.

Findings

Discovery of three neutral absorption zones with different properties.

Evidence of a clumpy, wind-like absorber responding to source flux.

Detection of a constant, low-density absorber with unknown location.

Abstract

Between July 2012 and February 2013, NuSTAR and XMM-Newton performed four long-look joint obser- vations of the type 1.8 Seyfert, NGC 1365. We have analyzed the variable absorption seen in these observations in order to characterize the geometry of the absorbing material. Two of the observations caught NGC 1365 in an unusually low absorption state, revealing complexity in the multi-layer absorber which had previously been hidden. We find the need for three distinct zones of neutral absorption in addition to the two zones of ionized absorption and the Compton-thick torus previously seen in this source. The most prominent absorber is likely associated with broad line region clouds with column densities of around $\sim\,$10$^{23}$ cm$^{-2}$ and a highly clumpy nature as evidenced by an occultation event in February 2013. We also find evidence of a patchy absorber with a variable column around $\sim\,10^{22}$ cm$^{-2}$ and a line of sight covering fraction of 0.3$-$0.9 which responds directly to the intrinsic source flux, possibly due to a wind geometry. A full-covering, constant absorber with a low column density of $\sim\,1 \times$ 10$^{22}$ cm$^{-2}$ is also present, though the location of this low density haze is unknown.