Unveiling the physics behind the spectral variations of changing-look quasars with optical polarimetry

Marin, Frédéric

doi:10.1051/0004-6361/201731726

Cited by 17 publications

(18 citation statements)

References 46 publications

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“…This result supports the variable accretion rate scenario as suggested by [21]. Afterwards, [35] reinforced the use of polarimetry as a diagnostic tool by modeling the optical continuum polarization expected from CL AGN in a transition from type 1 to type 2. The author carried out simulations for the two described scenarios, variable accretion rate and variable obscuration, using the Monte Carlo radiative transfer code STOKES [36,37].…”

Section: Changing-look Scenario and Optical Polarimetry As A Diagnostsupporting

confidence: 83%

A Changing-Look AGN to Be Probed by X-ray Polarimetry

2018

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Active galactic nuclei (AGN) produce the highest intrinsic luminosities in the Universe from within a compact region. The central engine is thought to be powered by accretion onto a supermassive black hole. A fraction of this huge release of energy influences the evolution of the host galaxy, and in particular, star formation. Thus, AGN are key astronomical sources not only because they play an important role in the evolution of the Universe, but also because they constitute a laboratory for extreme physics. However, these objects are under the resolution limit of current telescopes. Polarimetry is a unique technique capable of providing us with information on physical AGN structures. The incoming new era of X-ray polarimetry will give us the opportunity to explore the geometry and physical processes taking place in the innermost regions of the accretion disc. Here we exploit this future powerful tool in the particular case of changing-look AGN, which are key for understanding the complexity of AGN physics.

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Section: Changing-look Scenario and Optical Polarimetry As A Diagnostsupporting

confidence: 83%

A Changing-Look AGN to Be Probed by X-ray Polarimetry

2018

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“…In this phase, the intensity in the broad component of a spectral line is too weak that probably the AP15 method could not be used. Another technique must be used to explore the geometry of the object, such as proved by Hutsemékers et al (2017) and Marin (2017).…”

Section: Observationsmentioning

confidence: 99%

AGN black hole mass estimates using polarization in broad emission lines

Savić

Goosmann

Popović

et al. 2018

A&A

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Context. The innermost regions in active galactic nuclei (AGNs) were not being spatially resolved so far but spectropolarimetry can provide us insight about their hidden physics and the geometry. From spectropolarimetric observations in broad emission lines and assuming equatorial scattering as a dominant polarization mechanism, it is possible to estimate the mass of supermassive black holes (SMBHs) residing in the AGN center. Aims. We explore the possibilities and limits and put constraints on the usage of the method for determining SMBH masses using polarization in broad emission lines by providing more in-depth theoretical modeling. Methods. We use the Monte Carlo radiative transfer code stokes for exploring polarization properties of Type 1 AGNs. We model equatorial scattering using flared-disk geometry for a set of different SMBH masses assuming Thomson scattering. In addition to the Keplerian motion which is assumed to be dominant in the broad line region (BLR), we also consider cases of additional radial inflows and vertical outflows. Results. We model the profiles of polarization plane position angle ϕ, degree of polarization and total unpolarized line for different BLR geometries and different SMBH masses. Our modeling confirms that the method can be widely used for Type-1 AGNs when viewing inclinations are between 25• and 45• . We show that the distance between the BLR and scattering region (SR) has a significant impact on the mass estimates and the best mass estimates are when the SR is situated at the distance 1.5-2.5 times larger than the outer BLR radius. Conclusions. Our models show that if Keplerian motion can be traced through the polarized line profile, then the direct estimation of the mass of the SMBH can be performed. When radial inflows or vertical outflows are present in the BLR, this method can still be applied if velocities of the inflow/outflow are less than 500 km s −1 . We also find that models for NGC 4051, NGC 4151, 3C 273 and PG0844+349 are in good agreements with observations.

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“…LaMassa et al 2015;Ruan et al (2016); MacLeod et al 2016;Runnoe et al 2016;McElroy et al 2016;Gezari et al 2017). Possible explanations for this phenomenon include changes in accretion rate (e.g., Marin 2017). On longer timescales, >10 4 yr, AGN variability is probed through extended AGN photoionised emission line regions (EELR) such as the Voorwerpjes (VP, e.g., Lintott et al 2009;Gagne et al 2011;Keel et al 2012;Keel et al 2017;Sartori et al 2016;Sartori et al 2018) or ionisation and radio structures in our own Milky Way (e.g., Su et al look quasars" are used inconsistently throughout the literature, and can refer to changes both in emission line width or obscuration, as well as in luminosity.…”

Section: Introductionmentioning

confidence: 98%

A model for AGN variability on multiple time-scales

Sartori

Schawinski

Trakhtenbrot

et al. 2018

Monthly Notices of the Royal Astronomical Society: Letters

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We present a framework to link and describe AGN variability on a wide range of timescales, from days to billions of years. In particular, we concentrate on the AGN variability features related to changes in black hole fuelling and accretion rate. In our framework, the variability features observed in different AGN at different timescales may be explained as realisations of the same underlying statistical properties. In this context, we propose a model to simulate the evolution of AGN light curves with time based on the probability density function (PDF) and power spectral density (PSD) of the Eddington ratio (L/L Edd ) distribution. Motivated by general galaxy population properties, we propose that the PDF may be inspired by the L/L Edd distribution function (ERDF), and that a single (or limited number of) ERDF+PSD set may explain all observed variability features. After outlining the framework and the model, we compile a set of variability measurements in terms of structure function (SF) and magnitude difference. We then combine the variability measurements on a SF plot ranging from days to Gyr. The proposed framework enables constraints on the underlying PSD and the ability to link AGN variability on different timescales, therefore providing new insights into AGN variability and black hole growth phenomena.

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Unveiling the physics behind the spectral variations of changing-look quasars with optical polarimetry

Cited by 17 publications

References 46 publications

A Changing-Look AGN to Be Probed by X-ray Polarimetry

A Changing-Look AGN to Be Probed by X-ray Polarimetry

AGN black hole mass estimates using polarization in broad emission lines

A model for AGN variability on multiple time-scales

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