Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

Mathur, S.; Gupta, Anjali; Page, K. L.; Pogge, Richard W.; Krongold, Y.; Goad, M. R.; Adams, S. M.; Arévalo, P.; Barth, Aaron J.; Bazhaw, C.; Beatty, Thomas G.; Bentz, Misty C.; Bigley, A.; Bisogni, S.; Borman, G. A.; Boroson, Todd A.; Bottorff, M. C.; Brandt, W. N.; Breeveld, A. A.; Brown, J. E.; Brown, J. S.; Cackett, Edward M.; Canalizo, Gabriela; Carini, M. T.; Clubb, K. I.; Comerford, Julia M.; Coker, Carl T.; Corsini, E. M.; Crenshaw, D. Michael; Croft, Steve; Croxall, K. V.; Bontà, E. Dalla; Deason, Alis J.; Denney, K. D.; Lorenzo-Cáceres, A. de; Rosa, Gisella De; Dietrich, M.; Edelson, R.; Ely, Justin; Eracleous, Michael; Evans, P. A.; Fausnaugh, Michael; Ferland, Gary J.; Filippenko, A. V.; Flatland, K.; Fox, O.; Gates, E. L.; Gehrels, N.; Geier, S.; Gelbord, Jonathan; Gorjian, Varoujan; Greene, Jenny E.; Grier, C. J.; Grupe, D.; Hall, Patrick B.; Henderson, Calen B.; Hicks, S.; Holmbeck, Erika M.; Holoien, T. W. S.; Horenstein, D.; Horne, K.; Hutchison, Taylor A.; Im, Myungshin; Jensen, J. J.; Johnson, C. A.; Joner, M. D.; Jones, Jeremy; Kaastra, J. S.; Kaspi, S.; Kelly, Brandon C.; Kelly, Patrick L.; Kennea, J. A.; Kim, M.; Kim, S.; Kim, S. C.; King, A.; Klimanov, S. A.; Kochanek, C. S.; Korista, K. T.; Kriss, Gerard A.; Lau, Marie Wingyee; Lee, J. C.; Leonard, Douglas C.; Li, M.; Lira, P.; Ma, Zhiyuan; MacInnis, F.; Manne-Nicholas, E. R.; Malkan, Matthew A.; Mauerhan, Jon C.; McGurk, Rosalie; McHardy, I. M.; Montouri, C.; Morelli, L.; Mosquera, A. M.; Mudd, D.; Müller–Sánchez, F.; Musso, R.; Назаров, С. В.; Netzer, H.; Nguyen, M. L.; Norris, R. P.; Nousek, J. A.; Ochner, P.; Okhmat, D. N.; Ou-Yang, B.; Pancoast, Anna; Papadakis, I. E.; Parks, J. R.; Pei, L.; Peterson, B. M.; Pizzella, A.; Poleski, R.; Pott, Jörg-Uwe; Rafter, Stephen E.; Rix, Hans─Walter; Runnoe, Jessie C.; Saylor, D. A.; Schimoia, J. S.; Schnülle, K.; Сергеев, С. Г.; Shappee, B. J.; Shivvers, I.; Siegel, M. H.; Simonian, G.; Siviero, A.; Skielboe, A.; Somers, Garrett; Spencer, M.; Starkey, D.; Stevens, Daniel J.; Sung, Hyun-Il; Tayar, Jamie; Tejos, Nicolás; Turner, C. S.; Uttley, P.; Saders, Jennifer L. van; Vestergaard, M.; Vican, Laura; Villanueva, Steven; Villforth, C.; Weiss, Y.; Woo, Jong-Hak; Yan, Hao; Young, S.; Yuk, H.; Zheng, W.; Zhu, Wei; Zu, Ying

doi:10.3847/1538-4357/aa832b

Cited by 37 publications

(28 citation statements)

References 29 publications

(36 reference statements)

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“…That is, the probability that the required α for Zw 229-15 is smaller than that for kplr12158940 is less than 10% × 10% = 1%. uum is preferentially suppressed due to, e.g., the intrinsic change of the corona/disk structure (Mathur et al 2017;Sun et al 2018b) or external variations in line-of-sight obscuration (Dehghanian et al 2019;Kriss et al 2019). Indeed, if we split the full multi-wavelength light curves of NGC 5548 into two segments at HJD − 2450000 < 6747, the first portions are more variable than the second ones, especially on timescales longer than 10 days (see Figure 5 of Sun et al 2018b).…”

Section: Ngc 5548mentioning

confidence: 99%

Corona-heated Accretion-disk Reprocessing: A Physical Model to Decipher the Melody of AGN UV/Optical Twinkling

Xue

Brandt

et al. 2020

ApJ

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Active galactic nuclei (AGNs) have long been observed to "twinkle" (i.e., their brightness varies with time) on timescales from days to years in the UV/optical bands. Such AGN UV/optical variability is essential for probing the physics of supermassive black holes (SMBHs), the accretion disk, and the broad-line region. Here we show that the temperature fluctuations of an AGN accretion disk, which is magnetically coupled with the corona, can account for observed high-quality AGN optical light curves. We calculate the temperature fluctuations by considering the gas physics of the accreted matter near the SMBH. We find that the resulting simulated AGN UV/optical light curves share the same statistical properties as the observed ones as long as the dimensionless viscosity parameter α, which is widely believed to be controlled by magnetohydrodynamic (MHD) turbulence in the accretion disk, is about 0.01-0.2. Moreover, our model can simultaneously explain the larger-thanexpected accretion disk sizes and the dependence of UV/optical variability upon wavelength for NGC 5548. Our model also has the potential to explain some other observational facts of AGN UV/optical variability, including the timescale-dependent bluer-when-brighter color variability and the dependence of UV/optical variability on AGN luminosity and black hole mass. Our results also demonstrate a promising way to infer the black-hole mass, the accretion rate, and the radiative efficiency, thereby facilitating understanding of the gas physics and MHD turbulence near the SMBH and its cosmic mass growth history by fitting the AGN UV/optical light curves in the era of time-domain astronomy.

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Section: Ngc 5548mentioning

confidence: 99%

Corona-heated Accretion-disk Reprocessing: A Physical Model to Decipher the Melody of AGN UV/Optical Twinkling

Xue

Brandt

et al. 2020

ApJ

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“…The origin of this variation is not well understood. It may appear because the observed continuum is not the relevant extreme UV ionizing continuum, or due to the change of the line-of-sight covering factor of the obscurers absorbing the soft X-rays (e.g., Mathur et al 2017;Dehghanian et al 2018;Goad et al 2019;Kriss et al 2019).…”

Section: Varying Backgroundsmentioning

confidence: 99%

On reverberation mapping lag uncertainties

Kochanek

Peterson

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We broadly explore the effects of systematic errors on reverberation mapping lag uncertainty estimates from JAVELIN and the interpolated cross-correlation function (ICCF) method. We focus on simulated lightcurves from random realizations of the lightcurves of five intensively monitored AGNs. Both methods generally work well even in the presence of systematic errors, although JAVELIN generally provides better error estimates. Poorly estimated lightcurve uncertainties have less effect on the ICCF method because, unlike JAVELIN, it does not explicitly assume Gaussian statistics. Neither method is sensitive to changes in the stochastic process driving the continuum or the transfer function relating the line lightcurve to the continuum. The only systematic error we considered that causes significant problems is if the line lightcurve is not a smoothed and shifted version of the continuum lightcurve but instead contains some additional sources of variability.

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“…Use of changes in the velocity profile of emission lines can allow the structure of the BLR to be mapped (e.g., Welsh & Horne 1991;Horne et al 2004). Recent developments in modeling (Brewer et al 2011;Pancoast et al 2014), along with better data, have started to improve our understanding of the structure of the BLR, especially the recent AGN STORM campaign to monitor NGC5548 (De Rosa et al 2015;Edelson et al 2015;Fausnaugh et al 2016;Goad et al 2016;Mathur et al 2017;Pei et al 2017;Starkey et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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

Cackett

Chiang

McHardy

et al. 2018

ApJ

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133

186

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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.

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Space Telescope and Optical Reverberation Mapping Project. VII. Understanding the Ultraviolet Anomaly in NGC 5548 with X-Ray Spectroscopy

Cited by 37 publications

References 29 publications

Corona-heated Accretion-disk Reprocessing: A Physical Model to Decipher the Melody of AGN UV/Optical Twinkling

Corona-heated Accretion-disk Reprocessing: A Physical Model to Decipher the Melody of AGN UV/Optical Twinkling

On reverberation mapping lag uncertainties

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

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