A Partial Eclipse of the Heart: The Absorbed X-ray Low State in Mrk 1048

TL;DR

This study reports on XMM-Newton observations of Mrk 1048's low X-ray flux state, attributing it to a partial covering neutral absorber, likely a small cloud near the source, with minimal impact on optical/UV emissions.

Contribution

First to model the low flux state in Mrk 1048 as caused by a partial covering neutral absorber using spectral fitting and physical constraints.

Findings

X-ray flux drops by factor of 4-5 below 1 keV

Spectral differences explained by partial covering neutral absorber

Absorber likely a small cloud at ~10^18 cm from the source

Abstract

We present two new XMM-Newton observations of an unprecedented low flux state in the Seyfert 1 Mrk 1048 (NGC 985), taken in 2013. The X-ray flux below 1 keV drops by a factor of 4-5, whereas the spectrum above 5 keV is essentially unchanged. This points towards an absorption origin for the low state, and we confirm this with spectral fitting, finding that the spectral differences can be well modelled by the addition of a partial covering neutral absorber, with a column density of $\sim3\times 10^{22}$~cm$^{-2}$ and a covering fraction of $\sim0.6$. The optical and UV fluxes are not affected, and indeed are marginally brighter in the more recent observations, suggesting that only the inner regions of the disk are affected by the absorption event. This indicates either that the absorption is due to a cloud passing over the inner disk, obscuring the X-ray source but leaving the outer disk untouched, or that the absorber is dust-free so the UV continuum is unaffected. We use arguments based on the duration of the event and the physical properties of the absorber to constrain its size and location, and conclude that it is most likely a small cloud at $\sim10^{18}$cm from the source.