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 $N_ ext{H}$ 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 $log(N_ ext{H}/ ext{cm}^{-2})=22.9^{+0.3}_{-0.1}$. 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 $log(\xi/ ext{erg cm s}^{-1})=1.4^{+0.6}_{-0.2}$. 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 $rgtrsim0.5$ pc.

Serafinelli, R., Braito, V., Severgnini, P., Tombesi, F., Giani, G., Piconcelli, E., et al. (2021). X-ray obscuration from a variable ionized absorber in PG 1114+445. ASTRONOMY & ASTROPHYSICS, 654 [10.1051/0004-6361/202141474].

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

Tombesi, F
Membro del Collaboration Group
;
Vagnetti, F
Membro del Collaboration Group
;
2021-10-01

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 $N_ ext{H}$ 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 $log(N_ ext{H}/ ext{cm}^{-2})=22.9^{+0.3}_{-0.1}$. 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 $log(\xi/ ext{erg cm s}^{-1})=1.4^{+0.6}_{-0.2}$. 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 $rgtrsim0.5$ pc.
ott-2021
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore FIS/05 - ASTRONOMIA E ASTROFISICA
English
Con Impact Factor ISI
astro-ph.GA
astro-ph.HE
http://arxiv.org/abs/2107.06584v1
Serafinelli, R., Braito, V., Severgnini, P., Tombesi, F., Giani, G., Piconcelli, E., et al. (2021). X-ray obscuration from a variable ionized absorber in PG 1114+445. ASTRONOMY & ASTROPHYSICS, 654 [10.1051/0004-6361/202141474].
Serafinelli, R; Braito, V; Severgnini, P; Tombesi, F; Giani, G; Piconcelli, E; Della Ceca, R; Vagnetti, F; Gaspari, M; Saturni, F; Middei, R; Tortosa,...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/276705
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