The origin of intrinsic variability of intraday variable sources

Roland, J.; Britzen, S.; Witzel, A.; Zensus, J. A.

doi:10.1051/0004-6361/200810709

Cited by 11 publications

(7 citation statements)

References 36 publications

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“…We conclude, remarking that if the inner parts of the accretion disk contain a warp or precess faster than the precession of the outer part, this will produce a very small perturbation that will produce a day-to-month variability of the core flux (Roland et al 2009). Solutions 1 and 5 are excluded because they have γ c > 30 .…”

Section: Discussionmentioning

confidence: 98%

Binary black holes in nuclei of extragalactic radio sources

Roland¹,

Britzen²,

Caproni³

et al. 2013

A&A

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If we assume that nuclei of extragalactic radio sources contain binary black hole systems, the two black holes can eject VLBI components, in which case two families of different VLBI trajectories will be observed. Another important consequence of a binary black hole system is that the VLBI core is associated with one black hole, and if a VLBI component is ejected by the second black hole, one expects to be able to detect the offset of the origin of the VLBI component ejected by the black hole that is not associated with the VLBI core. The ejection of VLBI components is perturbed by the precession of the accretion disk and the motion of the black holes around the center of gravity of the binary black hole system. We modeled the ejection of the component taking into account the two pertubations and present a method to fit the coordinates of a VLBI component and to deduce the characteristics of the binary black hole system. Specifically, this is the ratio T p /T b where T p is the precession period of the accretion disk and T b is the orbital period of the binary black hole system, the mass ratio M 1 /M 2 , and the radius of the binary black hole system R bin . From the variations of the coordinates as a function of time of the ejected VLBI component, we estimated the inclination angle i o and the bulk Lorentz factor γ of the modeled component. We applied the method to component S1 of 1823+568 and to component C5 of 3C 279, which presents a large offset of the space origin from the VLBI core. We found that 1823+568 contains a binary black hole system whose size is R bin ≈ 60 µas (µas is a microarcsecond) and 3C 279 contains a binary black hole system whose size is R bin ≈ 420 µas. We calculated the separation of the two black holes and the coordinates of the second black hole from the VLBI core. This information will be important to link the radio reference-frame system obtained from VLBI observations and the optical reference-frame system obtained from Gaia.

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Section: Discussionmentioning

confidence: 98%

Binary black holes in nuclei of extragalactic radio sources

Roland¹,

Britzen²,

Caproni³

et al. 2013

A&A

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“…However, in the case of S5 0716+714, correlated variations at frequencies in the radio and the optical regimes indicate an intrinsic component to the variability. Roland et al (2009) found that the formation and the rotation of a warp in the inner part of the accretion disk produce a small perturbation of the relativistic beam and consequently a variation in the viewing angle and in the beamed synchrotron emission explaining IDV variations.…”

Section: Astrophysical Phenomena Involved In the Optical Flux Variatimentioning

confidence: 97%

Long-termRandV-band monitoring of some suitable targets for the link between ICRF and the futureGaiacelestial reference frame

Taris

Andrei

Roland

et al. 2016

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Context. The Gaia astrometric mission of the European Space Agency was launched on December 2013. It will provide a catalog of 500 000 quasars. Some of these targets will be chosen to build an optical reference system that will be linked to the International Celestial Reference Frame (ICRF). The astrometric coordinates of these sources will have roughly the same uncertainty at both optical and radio wavelengths, and it is then mandatory to observe a common set of targets to build the link. In the ICRF, some targets have been chosen because of their pointlikeness. They are quoted as defining sources, and they ensure very good uncertainty about their astrometric coordinates. At optical wavelengths, a comparable uncertainty could be achieved for targets that do not exhibit strong astrophysical phenomena, which is a potential source of photocenter flickering. A signature of these phenomena is a magnitude variation at optical wavelengths. Aims. The goal of this work is to present the time series of 14 targets suitable for the link between the ICRF and the future Gaia Celestial Reference Frame. The observations have been done systematically by robotic telescopes in France and Chile once every two nights since 2011 and in two filters. These time series are analyzed to search for periodic or quasi-periodic phenomena that must be taken into account when computing the uncertainty about the astrometric coordinates. Methods. Two independent methods were used in this work to analyze the time series. We used the CLEAN algorithm to compare the frequency obtained to those given by the Lomb-Scargle method. It avoids misinterpreting the frequency peaks given in the periodograms. Results. For the 14 targets we determine some periods with a confidence level above 90% in each case. Some of the periods found in this work were not previously known. For the others, we did a comparative study of the periods previously studied by others and always confirm their values. All the periods given by the two methods are in good agreement with the difference always below 7.9% in the worst case. Finally we also present the structure functions for our two sets of objects (BL Lac and Seyfert galaxies). Conclusions. For all but one target, we find variations that could be the signature of periodic or quasi-periodic phenomena. Our time series could allow to bring some constraints on astrophysical models that could explain such variations. Binary black hole system, instabilities in the jet or in the accretion disk, changes in the torus structure are some of these astrophysical phenomena. They must be kept in mind when evaluating the uncertainty about the astrometric position of the targets suitable for the link between reference systems in a conservative way.

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“…Usually, for the IDV light curve of blazars there is no significant pattern and period. Roland et al (2009) proposed that the formation and the rotation of a warp in the inner part of the accretion disk can lead to some perturbations of the beam that finally produce the observed IDV.…”

Section: Introductionmentioning

confidence: 99%

Fractal dimension and thermodynamic fluctuation properties of IDV light curves

Leung¹,

Wei²,

Kong³

et al. 2011

Res. Astron. Astrophys.

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Fractals are a basic tool to phenomenologically describe natural objects having a high degree of temporal or spatial variability. From a physical point of view the fractal properties of natural systems can also be interpreted by using the standard formalism of thermodynamical fluctuations. In the present paper we introduce and analyze the fractal dimension of the Intra -Day-Variability (IDV) light-curves of the BL Lac objects, in the optical, radio and X-ray bands, respectively. A general description of the fluctuation spectrum of these systems based on general thermodynamical principles is also proposed. Based on the general fractal properties of a given physical system, we also introduce the predictability index for the IDV light curves. We have explicitly determined the fractal dimension for the R-band observations of five blazars, as well as for the radio band observations of the compact extragalactic radio source J 1128+5925, and of several X-ray sources. Our results show that the fractal dimension of the optical and X-ray observations indicates an almost pure "Brownian noise" (random walk) spectrum, with a very low predictability index, while in the radio band the predictability index is much higher. We have also studied the spectral properties of the IDV light curves, and we have shown that their spectral index is very closely correlated with the corresponding fractal dimension.

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The origin of intrinsic variability of intraday variable sources

Cited by 11 publications

References 36 publications

Binary black holes in nuclei of extragalactic radio sources

Binary black holes in nuclei of extragalactic radio sources

Long-termRandV-band monitoring of some suitable targets for the link between ICRF and the futureGaiacelestial reference frame

Fractal dimension and thermodynamic fluctuation properties of IDV light curves

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