Photo-centric variability of quasars caused by variations in their inner structure: Consequences on Gaia measurements

Abstract

We study the photocenter position variability due to variations in the quasar inner structure. We consider variability in the accretion disk emissivity and torus structure variability due to different illumination by the central source. We discuss possible detection of these effects by Gaia. Observations of the photocenter variability in two AGNs, SDSS J121855+020002 and SDSS J162011+1724327 have been reported and discussed. With investigation of the variations in the quasar inner structure we explore how much this effect can affect the position determination and whether it can be (or not) detected with Gaia mission. We used (a) a model of a relativistic disk, including the perturbation that can increase brightness of a part of the disk, and consequently offset the photocenter position, and (b) a model of a dusty torus which absorbs and re-emits the incoming radiation from accretion disk. We estimated the value of the photocenter offset due to these two effects. We found that perturbations in the inner structure can significantly offset the photocenter. It depends on the characteristics of perturbation and accretion disk and structure of the torus. In the case of two considered QSOs the observed photocenter offsets cannot be explained by variations in the accretion disk and other effects should be considered. We discussed possibility of exploding stars very close to the AGN source, and also possibility that there are two variable sources in the center of these two AGNs that may indicate a binary super-massive black hole system on a kpc (pc) scale. The Gaia mission seems to be very perspective, not only for astrometry, but also for exploring the inner structure of AGNs. We conclude that variations in the quasar inner structure can affect the observed photocenter (up to several mas). There is a chance to observe such effect in the case of bright and low-redshifted QSOs.

12 pages, 8 figures, 3 tables. Accepted for publication in Astronomy and Astrophysics. Language improved, typos corrected

References in corpus (11)

• Radio-Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications
• A Close Look at Star Formation around Active Galactic Nuclei
• Efficient 3D NLTE dust radiative transfer with SKIRT
• Opacity in compact extragalactic radio sources and its effect on astrophysical and astrometric studies
• Cosmic Evolution of Mass Accretion Rate and Metalicity in Active Galactic Nuclei
• Radio Properties of Low Redshift Broad Line Active Galactic Nuclei
• HST Images and KPNO Spectroscopy of the Binary Black Hole Candidate SDSS J153636.22+044127.0
• Spectral optical monitoring of 3C 390.3 in 1995-2007: II. Variability of the spectral line parameters
• 3D Spectroscopic Study of the Line Emitting Regions of Mrk 493
• Observational Effects of Strong Gravity in Vicinity of Supermassive Black Holes
• X-ray Emission From Accretion Disks of AGN: Signatures of Supermassive Black Holes

Cited by in corpus (17)

• The dust covering factor in active galactic nuclei
• Star-galaxy Classification Using Deep Convolutional Neural Networks
• Gaia Data Release 1: The reference frame and the optical properties of ICRF sources
• Observational consequences of optical band milliarcsecond-scale structure in active galactic nuclei discovered by Gaia
• The optical variability of Supermassive Black Hole Binary Candidate PG1302-102: Periodicity and perturbation in the light curve
• Optical-radio positional offsets for active galactic nuclei
• Radio-Optical Reference Frame Link Using the US Naval Observatory Astrograph and Deep CCD Imaging
• Gaia reference frame amid quasar variability and proper motion patterns in the data
• Quasars can be used to verify the parallax zero-point of the Tycho-Gaia Astrometric Solution
• Composite profile of the Fe K$\alpha$ spectral line emitted from a binary system of supermassive black holes
• The Gaia-WISE Extragalactic Astrometric Catalog
• SQUAB I: The first release of Strange QUasar candidates with ABnormal astrometric characteristics from Gaia EDR3 and SDSS
• Spectro-photometric variability of quasars caused by lensing of diffuse massive substructure: Consequences on flux anomaly and precise astrometric measurements
• Broad spectral line and continuum variabilities in QSO spectra induced by microlensing of diffusive massive substructure
• The photocentre-AGN displacement: Is M87 actually harbouring a displaced supermassive black hole?
• The Host Galaxies of PTA Sources: Converting Supermassive BH Binary Parameters into EM Observables
• Toward a Measurement of the Transverse Peculiar Velocity of Galaxy Pairs