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X-ray obscuration from a variable ionized absorber in PG 1114+445

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arxiv 2107.06584 v1 pith:SZX42P3U submitted 2021-07-14 astro-ph.GA astro-ph.HE

X-ray obscuration from a variable ionized absorber in PG 1114+445

classification astro-ph.GA astro-ph.HE
keywords absorberstextx-raycampaigncolumndensityionizedobservations
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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Photoionized absorbers of outflowing gas are commonly found in the X-ray spectra of active galactic nuclei (AGN). While most of these absorbers are seldom significantly variable, some ionized obscurers have been increasingly found to substantially change their column density on a wide range of time scales. These $N_\text{H}$ variations are often considered as the signature of the clumpy nature of the absorbers. Here we present the analysis of a new Neil Gehrels Swift Observatory campaign of the type-1 quasar PG 1114+445, which was observed to investigate the time evolution of the multiphase outflowing absorbers previously detected in its spectra. The analyzed dataset consists of 22 observations, with a total exposure of $\sim90$ ks, spanning about $20$ months. During the whole campaign, we report an unusually low flux state with respect to all previous X-ray observations of this quasar. From the analysis of the stacked spectra we find a fully covering absorber with a column density $\log(N_\text{H}/\text{cm}^{-2})=22.9^{+0.3}_{-0.1}$. This is an order of magnitude higher than the column density measured in the previous observations. This is either due to a variation of the known absorbers, or by a new one, eclipsing the X-ray emitting source. We also find a ionization parameter of $\log(\xi/\text{erg cm s}^{-1})=1.4^{+0.6}_{-0.2}$. Assuming that the obscuration lasts for the whole duration of the campaign, i.e. more than $20$ months, we estimate the minimum distance of the ionized clump, which is located at $r\gtrsim0.5$ pc.

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  1. X-ray Absorption Variability in NGC 1142: Another Constraint on the Nature of the Torus/Broad-Line Region in Active Galactic Nuclei

    astro-ph.GA 2026-07 conditional novelty 4.5

    NGC 1142’s NH varies across nine epochs; detection probability scales with observation count, and simple cloud simulations favor many simultaneous eclipsing clouds.