Polarization of changing-look quasars

Hutsemékers, Damien; González, B. Agís; Marin, Frédéric; Sluse, Dominique; Almeida, C. Ramos; Pulido, J. A. Acosta

doi:10.1051/0004-6361/201834633

Cited by 61 publications

(46 citation statements)

References 55 publications

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“…Crucially, our use of changing-look quasars enables us to bypass both the issues of dust obscuration and M BH measurements. Since changing-look quasars are observed to be Type 1 AGN before their fading, and their fading has been shown to be consistent with a decrease in their Eddington ratio while disfavoring dust obscuration (LaMassa et al 2015;Ruan et al 2016;Runnoe et al 2016;MacLeod et al 2016;Hutsemékers et al 2017;Sheng et al 2017;Yang et al 2018;Stern et al 2018;Ross et al 2018;MacLeod et al 2019;Hutsemékers et al 2019), we know that their UV luminosities after they fade are also unobscured. Furthermore, changing-look quasars also allow us to estimate M BH for AGN at L bol /L Edd 10 −2 , since we can estimate M BH using the prominent broad emission lines in their bright state optical spectra, and then measure both their α OX and L bol /L Edd after they fade.…”

Section: Introductionmentioning

confidence: 94%

The Analogous Structure of Accretion Flows in Supermassive and Stellar Mass Black Holes: New Insights from Faded Changing-look Quasars

Ruan

Anderson

Eracleous

et al. 2019

ApJ

109

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Despite their factor of ∼10 8 difference in black hole mass, several lines of evidence suggest possible similarities between black hole accretion flows in active galactic nuclei (AGN) and Galactic X-ray binaries. However, it is still unclear whether the geometry of the disk-corona system in X-ray binaries directly scale up to AGN, and whether this analogy still holds in different accretion states. We test this AGN/X-ray binary analogy, by comparing the observed correlations between the UV-to-X-ray spectral index (α OX ) and Eddington ratio in AGN to those predicted from observations of X-ray binary outbursts. This approach probes the geometry of their disk-corona systems as they transition between different accretion states. We use new Chandra X-ray and ground-based rest-UV observations of faded 'changing-look' quasars to extend this comparison to lower Eddington ratios of <10 −2 , where observations of X-ray binaries predict a softening of α OX in AGN. We find that the observed correlations between α OX and Eddington ratio of AGN displays a remarkable similarity to accretion state transitions in prototypical X-ray binary outbursts, including an inversion of this correlation at a critical Eddington ratio of ∼10 −2 . Our results suggest that the structures of black hole accretion flows directly scale across a factor of ∼10 8 in black hole mass and across different accretion states, enabling us to apply theoretical models of X-ray binaries to explain AGN phenomenology.

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Section: Introductionmentioning

confidence: 94%

The Analogous Structure of Accretion Flows in Supermassive and Stellar Mass Black Holes: New Insights from Faded Changing-look Quasars

Ruan

Anderson

Eracleous

et al. 2019

ApJ

109

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“…Recent evidence from spectropolarimetry (e.g., Hutsemékers et al 2019) and mid-infrared (mid-IR) echo (Sheng et al 2017) implies that variable obscuration is a rather unlikely explanation for the CL-AGNs. The drastic spectral changes seen in CL-AGNs most plausibly come from the intrinsic changes in accretion power.…”

Section: Introductionmentioning

confidence: 99%

X-Ray Spectral Shape Variation in Changing-look Seyfert Galaxy SDSS J155258+273728

Dou

Yang

et al. 2020

ApJL

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We analyze the X-ray, optical, and mid-infrared data of a "changing-look" Seyfert galaxy SDSS J155258+273728 at z;0.086. Over a period of one decade (2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018), its broad Hα line intensity increased by a factor of ∼4. Meanwhile, the X-ray emission in 2014 as observed by Chandra was about five times brighter than that in 2010 by Suzaku, and the corresponding emissions in the V-band, mid-infrared W1 band brighten by ∼0.18, 0.32 mag, respectively. Moreover, the absorption in X-rays is moderate and stable, i.e.,~-N 10 cm H 21 2 , but the X-ray spectrum becomes harder in the 2014 Chandra bright state (i.e., photon index G = -+ 1.52 0.06 0.06 ) than that of the 2010 Suzaku low state (G = -+ 2.03 0.21 0.22 ). With an Eddington ratio being lower than a few percent, the inner region of the accretion disk in SDSS J155258+273728is likely a hot accretion flow. We then compile from literature the X-ray data of "changing-look" active galactic nuclei (AGNs), and find that they generally follow the well-established "V"-shaped correlation in AGNs, that is, above a critical turnover luminosity the X-ray spectra soften with the increasing luminosity, and below that luminosity the trend is reversed in the way of "harder when brighter." This presents direct evidence that CL-AGNs have distinctive changes in not only the optical spectral type, but also the X-ray spectral shape. The similarity in the X-ray spectral evolution between CL-AGNs and black hole X-ray binaries indicates that the observed CL-AGNs phenomena may relate to the state transition in accretion physics.

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“…The measurement of the polarization of changing-look AGNs can constrain the mechanism at the origin of their variations, while the time delay expected between the direct and the polarized light can be used to map the scattering regions (Hutsemékers et al 2017(Hutsemékers et al , 2019Marin 2017;Marin & Hutsemékers 2020). The polarization of Mrk 1018 was only measured once on February 9, 1986, by Goodrich (1989), who reported a linear polarization degree p = 0.28 ± 0.05% and a polarization position angle θ = 165 ± 5 • in the 4180−6903 Å optical band.…”

Section: Introductionmentioning

confidence: 99%

Spectropolarimetry of the changing-look active galactic nucleus Mrk 1018

Hutsemékers

González

Marin

et al. 2020

A&A

Self Cite

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We have obtained new spectropolarimetric observations at visible wavelengths of the changing-look active galactic nucleus (AGN) Mrk 1018. The AGN direct spectrum shows an extremely weak continuum with faint broad Hβ and Hα emission lines. Both lines can be fit with a single very broad emission line component of full width at half maximum FWHM 7200 km s −1 , with no evidence of the additional 3000 km s −1-wide component that was previously detected. While this is in agreement with line formation in a Keplerian disk, the line profile variability suggests that the broad emission line region is likely more complex. The continuum polarization of Mrk 1018 is low; it is not higher in the current faint state compared to the past bright state, confirming that dust obscuration is not the mechanism at the origin of the change of look. The polarization profile of the Hα line is asymmetric with no rotation of the polarization angle, which possibly reveals line formation in a polar outflow. Alternatively, the polarization profile may be the consequence of a time delay between the direct and the polarized light. Interestingly, the polarization signatures predicted for broad lines emitted around supermassive binary black holes are not observed.

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Polarization of changing-look quasars

Cited by 61 publications

References 55 publications

The Analogous Structure of Accretion Flows in Supermassive and Stellar Mass Black Holes: New Insights from Faded Changing-look Quasars

The Analogous Structure of Accretion Flows in Supermassive and Stellar Mass Black Holes: New Insights from Faded Changing-look Quasars

X-Ray Spectral Shape Variation in Changing-look Seyfert Galaxy SDSS J155258+273728

Spectropolarimetry of the changing-look active galactic nucleus Mrk 1018

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