X-ray spectroscopic survey of highly accreting AGN

Laurenti, M.; Piconcelli, E.; Zappacosta, L.; Tombesi, Francesco; Vignali, C.; Bianchi, S.; Marziani, Paola; Vagnetti, F.; Bongiorno, A.; Bischetti, M.; Olmo, A. del; Lanzuisi, G.; Luminari, A.; Middei, R.; Perri, M.; Ricci, Cláudio; Vietri, G.

doi:10.1051/0004-6361/202141829

“…Although our proposed obscuration scenario was based on the new sensitive NuSTAR observations of these three quasars, the general connection with obscuration from the disk wind suggests that this scenario may be applicable to the other intrinsically X-ray weak quasar candidates (e.g., those in Nardini et al 2019 andLaurenti et al 2022). Obscuration from the clumpy disk wind would predict X-ray variability from varying obscuration.…”

Section: Ra)iomentioning

confidence: 94%

NuSTAR Observations of Intrinsically X-Ray Weak Quasar Candidates: An Obscuration-only Scenario

Wang

¹

,

Brandt

²

,

Alexander

³

et al. 2022

ApJ

View full text Add to dashboard Cite

We utilize recent NuSTAR observations (co-added depth ≈55–120 ks) of PG 1001+054, PG 1254+047, and PHL 1811 to constrain their hard X-ray (≳5 keV) weakness and spectral shapes and thus to investigate the nature of their extreme X-ray weakness. These quasars showed very weak soft X-ray emission, and they were proposed to be intrinsically X-ray weak, with the X-ray coronae producing weak continuum emission relative to their optical/UV emission. However, the new observations suggest an alternative explanation. The NuSTAR 3–24 keV spectral shapes for PG 1001+054 and PHL 1811 are likely flat (effective power-law photon indices Γ eff = 1.0 − 0.6 + 0.5 and Γ eff = 1.4 − 0.7 + 0.8 , respectively), while the shape is nominal for PG 1254+047 (Γeff = 1.8 ± 0.3). PG 1001+054 and PHL 1811 are significantly weak at hard X-ray energies (by factors of ≈26–74 at rest-frame 8 keV) compared to the expectations from their optical/UV emission, while PG 1254+047 is only hard X-ray weak by a factor of ≈3. We suggest that X-ray obscuration is present in all three quasars. We propose that, as an alternative to the intrinsic X-ray weakness + X-ray obscuration scenario, the soft and hard X-ray weakness of these quasars can be uniformly explained under an obscuration-only scenario. This model provides adequate descriptions of the multiepoch soft and hard X-ray data of these quasars, with variable column density and leaked fraction of the partial covering absorber. We suggest that the absorber is the clumpy dust-free wind launched from the accretion disk. These quasars probably have super-Eddington accretion rates that drive powerful and high-density winds.

show abstract

“…First, we treat the primary parameters (θ, p, f D , Γ, α OX , and λ ion ) being independent of each other (see Figure 5 and other dependences in Appendices A-C). In reality, it has been reported, for instance, that some observable AGN measurements appear to be (tightly) correlated in various samples of AGN surveys (e.g., Γ, α OX , Eddington ratio, and monochromatic UV luminosities; Steffen et al 2006;Shemmer et al 2008;Luo et al 2014;Laurenti et al 2022). Although these correlations are preferentially suggested in highly accreting quasars, this may well be relevant for Seyfert 1s accreting at low Eddington rate.…”

Section: Summary and Discussionmentioning

confidence: 99%

Tell-tale Spectral Signatures of MHD-driven Ultrafast Outflows in AGNs

Fukumura

¹

,

Dadina²,

Matzeu

³

et al. 2022

ApJ

View full text Add to dashboard Cite

We aim to explore spectral signatures of the predicted multi-ion ultrafast outflows (UFOs) in the broadband X-ray spectra of active galactic nuclei by exploiting an accretion disk-wind model in the context of a simple magnetohydrodynamic (MHD) framework. We are focused primarily on examining the spectral dependences on a number of key properties: (1) ionizing luminosity ratio λ ion, (2) line-of-sight wind density slope p, (3) optical/UV-to-X-ray strength α OX, (4) inclination θ, (5) X-ray photon index Γ, and (6) wind density factor f D . With an emphasis on radio-quiet Seyferts in the sub-Eddington regime, multi-ion UFO spectra are systematically calculated as a function of these parameters to show that MHD-driven UFOs imprint a unique asymmetric absorption line profile with a pronounced blue tail structure on average. Such a characteristic line signature is generic to the simplified MHD disk-wind models presented in this work due to their specific kinematics and density structure. The properties of these absorption line profiles could be utilized as a diagnostics to distinguish between different wind-driving mechanisms or even the specific values of given MHD wind parameters. We also present high-fidelity microcalorimeter simulations in anticipation of the upcoming XRISM/Resolve and Athena/X-IFU instruments to demonstrate that such a “tell-tale” sign may be immune to a spectral contamination by the presence of additional warm absorbers and partially covering gas.

show abstract

“…As seen in Figure7, the apparent change of the entire spectrum is mostly explained by only variation in the covering fraction.In this study, the power-law photon index Γ is invariable between 2007 and 2016, except for X4. This might sound inconsistent with the widely-accepted "softer-when-brighter" trend of Seyfert galaxies (e.g.,Sobolewska & Papadakis 2009, Soldi et al 2014, Liu et al 2021,Laurenti et al 2022. We point out that considering the partial absorption, larger covering fractions cause a reduction of the soft X-rays and apparently flat spectra even when the intrinsic photon index is invariable.…”

mentioning

confidence: 79%

Simple interpretation of the seemingly complicated X-ray spectral variation of NGC 5548

Midooka,

Ebisawa,

Mizumoto

et al. 2022

Preprint

0

View full text Add to dashboard Cite

NGC 5548 is a very well-studied Seyfert 1 galaxy in broad wavelengths. Previous multiwavelength observation campaigns have indicated that its multiple absorbers are highly variable and complex. A previous study applied a two-zone partial covering model with different covering fractions to explain the complex X-ray spectral variation and reported a correlation between one of the covering fractions and the photon index of the power-law continuum. However, it is not straightforward to physically understand such a correlation. In this paper, we propose a model to avoid this unphysical situation; the central X-ray emission region is partially covered by clumpy absorbers composed of double layers. These "double partial coverings" have precisely the same covering fraction. Based on our model, we have conducted an extensive spectral study using the data taken by XMM-Newton, Suzaku, and NuSTAR in the range of 0.3-78 keV for 16 years. Consequently, we have found that the X-ray spectral variations are mainly explained by independent changes of the following three components;(1) the soft excess spectral component below ∼1 keV, (2) the cut-off power-law normalization, and (3) the partial covering fraction of the clumpy absorbers. In particular, spectral variations above ∼1 keV are mostly explained only by the changes of the partial covering fraction and the power-law normalization. In contrast, the photon index and all the other spectral parameters are not significantly variable.

show abstract

X-ray spectroscopic survey of highly accreting AGN

Cited by 22 publications

References 116 publications

NuSTAR Observations of Intrinsically X-Ray Weak Quasar Candidates: An Obscuration-only Scenario

NuSTAR Observations of Intrinsically X-Ray Weak Quasar Candidates: An Obscuration-only Scenario

Tell-tale Spectral Signatures of MHD-driven Ultrafast Outflows in AGNs

Simple interpretation of the seemingly complicated X-ray spectral variation of NGC 5548

Contact Info

Product

Resources

About