A rapid occultation event in NGC 3227

Turner, T. J.; Reeves, J. N.; Braito, V.; Lobban, A.; Kraemer, S. B.; Miller, L.

doi:10.1093/mnras/sty2447

Cited by 42 publications

(77 citation statements)

References 39 publications

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“…In particular, strong absorption is present in obs 6 (magenta), which is most prominent at ∼0.7-0.9 keV and is due to absorption by the UTA. This is the signature of the occultation event described in Turner et al (2018). Meanwhile, evidence of emission is apparent at higher energies, most notably in the form of a strong emission line at 6.4 keV due to near-neutral Fe K α.…”

Section: Spectral Decompositionmentioning

confidence: 76%

“…1. This difference in the shape of the spectrum in obs 6 formed the motivation behind the analysis in Turner et al (2018), where we show that NGC 3227 appeared to undergo a strong occultation event by a cloud of ionized gas manifesting itself in a strengthening of the depth of the UTA in the high-resolution RGS data. As such, we fitted obs 1-5 and obs 6 separately finding significant differences in the hardness-ratio slopes.…”

Section: Xsmentioning

confidence: 78%

“…This is the second in a series of papers on this co-ordinated XMM-Newton+NuSTAR campaign. Previously, in Turner et al (2018), we reported on a rapid occultation event occurring towards the end of the observing campaign. We detected significant spectral hardening of the source coupled with a measurable increase in the depth of the unresolved transition array (UTA), thanks to the highresolution Reflection Grating Spectrometer (RGS) on-board XMM-Newton.…”

Section: Introductionmentioning

confidence: 95%

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X-ray variability analysis of a large series of XMM–Newton +NuSTAR observations of NGC 3227

Lobban

Turner

Reeves

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present a series of X-ray variability results from a long XMM–Newton + NuSTAR campaign on the bright, variable AGN NGC 3227. We present an analysis of the light curves, showing that the source displays typically softer-when-brighter behaviour, although also undergoes significant spectral hardening during one observation which we interpret as due to an occultation event by a cloud of absorbing gas. We spectrally decompose the data and show that the bulk of the variability is continuum-driven and, through rms variability analysis, strongly enhanced in the soft band. We show that the source largely conforms to linear rms-flux behaviour and we compute X-ray power spectra, detecting moderate evidence for a bend in the power spectrum, consistent with existing scaling relations. Additionally, we compute X-ray Fourier time lags using both the XMM–Newton and – through maximum-likelihood methods – NuSTAR data, revealing a strong low-frequency hard lag and evidence for a soft lag at higher frequencies, which we discuss in terms of reverberation models.

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Section: Spectral Decompositionmentioning

confidence: 76%

Section: Xsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 95%

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X-ray variability analysis of a large series of XMM–Newton +NuSTAR observations of NGC 3227

Lobban

Turner

Reeves

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…Transient X-ray obscurers -outflowing, low-ionisation gas partially eclipsing the X-ray source -have been identified in a number of Seyfert galaxies (Risaliti et al 2007Kaastra et al 2014;Longinotti et al 2013Longinotti et al , 2019Ebrero et al 2016;Turner et al 2018). In this paper we made use of X-ray spectral-timing techniques (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…2). These so-called X-ray obscurers absorb significant amounts of UV and soft X-ray flux Kaastra et al 2014;Longinotti et al 2013Longinotti et al , 2019Ebrero et al 2016;Turner et al 2018), partially eclipsing the X-ray source and producing broad, blue-shifted UV absorption troughs (Kaastra et al 2014;Mehdipour et al 2017, hereafter M17;Kriss et al 2019, hereafter K19). Such obscuration events are transient (Markowitz et al 2014), covering a diverse range of timescales, from a few hours (e.g.…”

Section: Introductionmentioning

confidence: 99%

Incoherent fast variability of X-ray obscurers

Marco

Adhikari

Ponti

et al. 2020

A&A

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Context. Obscuration events caused by outflowing clumps or streams of high column density and low ionised gas, shown to absorb the X-ray continuum heavily, have been witnessed across a number of Seyfert galaxies. Aims. We report on the X-ray spectral-timing analysis of the December 2016 obscuration event in NGC 3783, which was aimed at probing variability of the X-ray obscurer on the shortest possible timescales. The main goals of this study are to obtain independent constraints on the density and, ultimately on the distance of the obscuring gas, as well as to characterise the impact of variable obscuration on the observed X-ray spectral-timing characteristics of Seyfert galaxies. Methods. We carried out a comparative analysis of NGC 3783 during unobscured (using archival 2000–2001 XMM-Newton data) and obscured states (using XMM-Newton and NuSTAR data from the 2016 observational campaign). The analysed timescales range between ten hours and about one hour. This study was then generalised to discuss the signatures of variable obscuration in the X-ray spectral-timing characteristics of Seyfert galaxies as a function of the physical properties of the obscuring gas. Results. The X-ray obscurer in NGC 3783 is found to vary on timescales between about one hour to ten hours. This variability is incoherent with respect to the variations of the X-ray continuum. A fast response (on timescales shorter than about 1.5 ks) of the ionisation state of the obscuring gas to the short timescale variability of the primary X-ray continuum provides a satisfactory interpretation of all the observed X-ray spectral-timing properties. This study enabled us to put independent constraints on the density and location of the obscuring gas. We found the gas to have a density of ne > 7.1 × 107 cm−3, which is consistent with a location in the broad line region.

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Photoionized emission and absorption features in the high-resolution X-ray spectra of NGC 3783

Mao

Mehdipour

Kaastra

et al. 2019

A&A

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Our Swift monitoring program triggered two joint XMM-Newton, NuSTAR and HST observations on 11 and 21 December 2016 targeting NGC 3783, as its soft X-ray continuum was heavily obscured. Consequently, emission features, including the O vii radiative recombination continuum, stand out above the diminished continuum. We focus on the photoionized emission features in the December 2016 RGS spectra, and compare them to the time-averaged RGS spectrum obtained in 2000-2001 when the continuum was unobscured. A two-phase photoionized plasma is required to account for the narrow emission features. These narrow emission features are weakly varying between 2000-2001 and December 2016. We also find a statistically significant broad emission component in the time-averaged RGS spectrum in 2000-2001. This broad emission component is significantly weaker in December 2016, suggesting that the obscurer is farther away than the X-ray broad-line region. In addition, by analyzing the archival high-resolution X-ray spectra, we find that nine photoionized absorption components with different ionization parameters and kinematics are required for the warm absorber in X-rays.

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A rapid occultation event in NGC 3227

Cited by 42 publications

References 39 publications

X-ray variability analysis of a large series of XMM–Newton +NuSTAR observations of NGC 3227

X-ray variability analysis of a large series of XMM–Newton +NuSTAR observations of NGC 3227

Incoherent fast variability of X-ray obscurers

Photoionized emission and absorption features in the high-resolution X-ray spectra of NGC 3783

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