English

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

Astrophysics of Galaxies 2021-10-13 v1 High Energy Astrophysical Phenomena

Abstract

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 NHN_\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 90\sim90 ks, spanning about 2020 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(NH/cm2)=22.90.1+0.3\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(ξ/erg cm s1)=1.40.2+0.6\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 2020 months, we estimate the minimum distance of the ionized clump, which is located at r0.5r\gtrsim0.5 pc.

Keywords

Cite

@article{arxiv.2107.06584,
  title  = {X-ray obscuration from a variable ionized absorber in PG 1114+445},
  author = {R. Serafinelli and V. Braito and P. Severgnini and F. Tombesi and G. Giani and E. Piconcelli and R. Della Ceca and F. Vagnetti and M. Gaspari and F. G. Saturni and R. Middei and A. Tortosa},
  journal= {arXiv preprint arXiv:2107.06584},
  year   = {2021}
}

Comments

7 pages, 7 figures, 3 tables. Accepted for publication in Astronomy & Astrophysics

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