Ultraviolet and X-ray variability of active galactic nuclei with<i>Swift</i>

Buisson, D. J. K.; Lohfink, A.; Alston, W. N.; Fabian, A. C.

doi:10.1093/mnras/stw2486

Cited by 79 publications

(96 citation statements)

References 134 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We estimate a range for the bolometric luminosity of ∼ 0.3 − 3.0 L Edd (with the uncertainty mainly driven by the blackbody temperature adopted). This agrees with Sani et al (2010) and the average measurements of Buisson et al (2017) ) using an additional blackbody for the UV emission from thin disc.…”

Section: High Eddington Accretion?supporting

confidence: 89%

Ultrafast outflows disappear in high-radiation fields

Pinto

Alston

Parker

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

Ultrafast outflows (UFOs) are the most extreme winds launched by active galactic nuclei (AGN) due to their mildly-relativistic speeds (∼ 0.1 − 0.3c) and are thought to significantly contribute to galactic evolution via AGN feedback. Their nature and launching mechanism are however not well understood. Recently, we have discovered the presence of a variable UFO in the narrow-line Seyfert 1 IRAS 13224−3809. The UFO varies in response to the brightness of the source. In this work we perform fluxresolved X-ray spectroscopy to study the variability of the UFO and found that the ionisation parameter is correlated with the luminosity. In the brightest states the gas is almost completely ionised by the powerful radiation field and the UFO is hardly detected. This agrees with our recent results obtained with principal component analysis. We might have found the tip of the iceberg: the high ionisation of the outflowing gas may explain why it is commonly difficult to detect UFOs in AGN and possibly suggest that we may underestimate their actual feedback. We have also found a tentative correlation between the outflow velocity and the luminosity, which is expected from theoretical predictions of radiation-pressure driven winds. This trend is rather marginal due to the Fe XXV-XXVI degeneracy. Further work is needed to break such degeneracy through time-resolved spectroscopy.

show abstract

Section: High Eddington Accretion?supporting

confidence: 89%

Ultrafast outflows disappear in high-radiation fields

Pinto

Alston

Parker

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…4). Such lags favor the X-ray reprocessing scenario at accretion disk and have been reported in many AGNs where UV is found to be lagging behind X-ray emission as expected in the reprocessing scenario (e.g., Buisson et al 2017;McHardy et al 2014McHardy et al , 2018. Additional support for this comes from the general variability trend of OJ 287 where multi-wavelength variations are normally simultaneous on short timescales (Kushwaha et al 2018a(Kushwaha et al , 2013 with lag reported only when an additional emission component was competing with its general emission (Kushwaha et al 2018b).…”

Section: Radio-quiet Agn/disk Based Modelsmentioning

confidence: 61%

Strong Soft X-Ray Excess in 2015 XMM-Newton Observations of BL Lac OJ 287

Pal

Kushwaha

Dewangan

et al. 2020

ApJ

View full text Add to dashboard Cite

We report a strong soft X-ray excess in the BL-Lacartae γ-ray blazar OJ 287 during the long exposure in May 2015, amongst two of the latest XMM-Newton observations performed in May 2015 and 2018. In case of May 2015 observation, a logparabola model fits the EPIC-pn data well while a logparabola plus powerlaw describes the overall simultaneous optical to X-ray spectra, suggesting the excess as the synchrotron tail. This interpretation, however, is inconsistent with the observed spectral break between near-infrared and optical spectra, attributed to standard disk around a supermassive black hole (SMBH). Based on this, we considered two commonly invoked accretion disk based models in AGNs to explain the soft excess: the cool Comptonization component in the accretion disk and the blurred reflection from the partially ionized accretion disk. We found that both cool Comptonization and blurred reflection models provide equally good fit to the data and favor a super-heavy SMBH of mass ∼ 10 10 M ⊙ . Further investigation of about a month long simultaneous X-ray and UV pointing observations revealed a delayed UV emission with respect to the 1.5-10 keV band, favoring X-ray reprocessing phenomenon as the dominant mechanism. The results suggest that the soft excess is probably caused by strong light bending close to the SMBH. The detected soft excess in 2015 data and its disappearance in 2018 data is also consistent with the presence of accretion disk emission, inferred from the NIR-optical spectral break between

show abstract

“…This is the equivalent to the disks being too big (the lag too large) by a factor of 1.6 based on the observed flux compared to the accretion disk model. More recently, observations of NGC2617 (Shappee et al 2014), NGC3516 (Noda et al 2016), NGC6814 (Troyer et al 2016), Fairall9 (Pal et al 2017), Ark120 (Gliozzi et al 2017), and a sample of 21 AGNs in the Swift archive (Buisson et al 2017) all find lags that are longer than expected for a standard thin disk. Both Pan-STARRS and the Dark Energy Survey (DES) are obtaining light curves of quasars in multiple photometric bands, allowing for determination of the average sizes from a large number of objects (Jiang et al 2017;Mudd et al 2017).…”

Section: Introductionmentioning

confidence: 98%

Accretion Disk Reverberation with Hubble Space Telescope Observations of NGC 4593: Evidence for Diffuse Continuum Lags

Cackett

Chiang

McHardy

et al. 2018

ApJ

143

186

View full text Add to dashboard Cite

The Seyfert 1 galaxy NGC 4593 was monitored spectroscopically with the Hubble Space Telescope as part of a reverberation mapping campaign that also included Swift, Kepler, and ground-based photometric monitoring. During 2016 July 12-August 6, we obtained 26 spectra across a nearly continuous wavelength range of ∼1150-10000 Å. These were combined with Swift data to produce a UV/optical "lag spectrum," which shows the interband lag relative to the Swift UVW2 band as a function of wavelength. The broad shape of the lag spectrum appears to follow the τ ∝ λ 4/3 relation seen previously in photometric interband lag measurements of other active galactic nuclei (AGNs). This shape is consistent with the standard thin disk model, but the magnitude of the lags implies a disk that is a factor of ∼3 larger than predicted, again consistent with what has been previously seen in other AGNs. In all cases these large disk sizes, which are also implied by independent gravitational microlensing of higher-mass AGNs, cannot be simply reconciled with the standard model. However, the most striking feature in this higher-resolution lag spectrum is a clear excess around the 3646 Å Balmer jump. This strongly suggests that diffuse emission from gas in the much larger broad-line region (BLR) must also contribute significantly to the interband lags. While the relative contributions of the disk and BLR cannot be uniquely determined in these initial measurements, it is clear that both will need to be considered to comprehensively model and understand AGN lag spectra.

show abstract

Ultraviolet and X-ray variability of active galactic nuclei withSwift

Cited by 79 publications

References 134 publications

Ultrafast outflows disappear in high-radiation fields

Ultrafast outflows disappear in high-radiation fields

Strong Soft X-Ray Excess in 2015 XMM-Newton Observations of BL Lac OJ 287

Accretion Disk Reverberation with Hubble Space Telescope Observations of NGC 4593: Evidence for Diffuse Continuum Lags

Contact Info

Product

Resources

About