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

Serafinelli, R.; Braito, V.; Severgnini, P.; Tombesi, F.; Giani, G.; Piconcelli, E.; Della Ceca, R.; Vagnetti, F.; Gaspari, M.; Saturni, F. G.; Middei, R.; Tortosa, A.

doi:10.48550/arxiv.2107.06584

Cited by 2 publications

(2 citation statements)

References 57 publications

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“…A growing number of transient X-ray obscuration events are being reported in Type I AGN (e.g., Lamer et al 2003;Risaliti et al 2007Risaliti et al , 2011Markowitz et al 2014;Kaastra et al 2014;Ebrero et al 2016;Mehdipour et al 2017;Longinotti et al 2019;Gallo et al 2021;Miller et al 2021;Serafinelli et al 2021). These events indicate that, in at least some type I AGN, our line of sight to the central engine is not always free.…”

Section: Introductionmentioning

confidence: 99%

Transient obscuration event captured in NGC 3227

Mao

Kaastra

Mehdipour

et al. 2022

A&A

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Context. A growing number of transient X-ray obscuration events in type I active galactic nuclei (AGN) suggest that our line of sight to the central engine is not always free. Multiple X-ray obscuration events were reported in the nearby Seyfert 1.5 galaxy NGC 3227 from 2000 to 2016. In late 2019, another X-ray obscuration event was identified with Swift. Two coordinated target-of-opportunity observations with XMM-Newton, NuSTAR, and the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) were triggered in November and December 2019 to study this obscuration event.Aims. We aim to constrain the physical properties of the absorbing material (i.e., the obscurer) that caused the X-ray obscuration event in late 2019. We also aim to compare the handful of obscuration events in NGC 3227 and other Seyfert galaxies. Methods. For each observation, we analyzed the time-averaged X-ray spectra collected with XMM-Newton and NuSTAR. We performed photoionization modeling with the SPEX code, which allows us to constrain the intrinsic continuum simultaneously with various photoionized absorption and emission components. Results. Similar to previous transient X-ray obscuration events in NGC 3227, the one caught in late 2019 is short-lived (less than five months). If the obscurer has only one photoionized component, the two X-ray observations in late 2019 cannot be explained by the same obscurer that responds to the varying ionizing continuum. Due to the unknown geometry of the obscurer, its number density and distance to the black hole cannot be well constrained. The inferred distance covers at least two orders of magnitude, from the broad-line region (BLR) to the dusty torus. Unlike some other X-ray obscuration events in Seyfert galaxies, such as NGC 5548 and NGC 3783, no prominent blueshifted, broad absorption troughs were found in the 2019 HST/COS spectra of NGC 3227 when compared with archival UV spectra. This might be explained if the X-ray obscurer does not intercept our line of sight to (a significant portion of) the UV-emitting region. Understanding the variety of observational differences in the X-ray obscuration events observed so far is not straightforward. Future observations with high-quality data are needed to unveil the nature of the X-ray obscuration events.

show abstract

Section: Introductionmentioning

confidence: 99%

Transient obscuration event captured in NGC 3227

Mao

Kaastra

Mehdipour

et al. 2022

A&A

View full text Add to dashboard Cite

show abstract

“…A growing number of transient X-ray obscuration events have been reported in Type I AGN (e.g., Lamer et al 2003;Risaliti et al 2007Risaliti et al , 2011Markowitz et al 2014;Kaastra et al 2014;Ebrero et al 2016;Mehdipour et al 2017;Longinotti et al 2019;Gallo et al 2021;Miller et al 2021;Serafinelli et al 2021). These events indicate that, in at least some type I AGN, our line-of-sight to the central engine is not always free.…”

Section: Introductionmentioning

confidence: 99%

Transient obscuration event captured in NGC 3227 III. Photoionization modeling of the X-ray obscuration event in 2019

Mao,

Kaastra,

Mehdipour

et al. 2022

Preprint

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Context. A growing number of transient X-ray obscuration events in type I active galactic nuclei (AGN) suggest that our line-ofsight to the central engine is not always free. Multiple X-ray obscuration events have been reported in the nearby Seyfert 1.5 galaxy NGC 3227 from 2000 to 2016. In late 2019, another X-ray obscuration event was identified with Swift. Two coordinated target-ofopportunity observations with XMM-Newton, NuSTAR, and the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) were triggered in November and December 2019 to study this obscuration event.Aims. We aim to constrain the physical properties of the absorbing material (namely, obscurer) that causes the X-ray obscuration event in late 2019. We also aim to compare the handful of obscuration events in NGC 3227 and other Seyfert galaxies. Methods. For each observation, we analyze the time-averaged X-ray spectra collected with XMM-Newton and NuSTAR. We perform photoionization modeling with the SPEX code, which allows us to constrain the intrinsic continuum simultaneously with various photoionized absorption and emission components. Results. Similar to previous transient X-ray obscuration events in NGC 3227, the one caught in late 2019 is short-lived (less than five months). If the obscurer has only one photoionized component, the two X-ray observations in late 2019 cannot be explained by the same obscurer that responds to the varying ionizing continuum. Due to the unknown geometry of the obscurer, its number density and distance to the black hole cannot be well constrained. The inferred distance covers at least two orders of magnitude, from the broadline region (BLR) to the dusty torus. Unlike some other X-ray obscuration events in Seyfert galaxies like NGC 5548 and NGC 3783, no prominent blueshifted broad absorption troughs were found in the 2019 HST/COS spectra of NGC 3227 when compared with archival UV spectra. This might be explained if the X-ray obscurer does not intercept our line of sight to (a significant portion of) the UV emitting region. It is not straightforward to understand the variety of the observational differences of the X-ray obscuration events observed so far. Future observations with high-quality data are needed to unveil the nature of the X-ray obscuration events.

show abstract

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

Cited by 2 publications

References 57 publications

Transient obscuration event captured in NGC 3227

Transient obscuration event captured in NGC 3227

Transient obscuration event captured in NGC 3227 III. Photoionization modeling of the X-ray obscuration event in 2019

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