Optical and radio variability of the BL Lacertae object AO 0235+16: A possible 5-6 year periodicity

Raiteri, C. M.; Villata, M.; Aller, H. D.; Aller, M. F.; Heidt, J.; Kurtanidze, O. M.; Lanteri, L.; Maesano, M.; Massaro, E.; Montagni, F.; Nesci, R.; Nilsson, K.; Nikolashvili, M. G.; Nurmi, P.; Ostorero, L.; Pursimo, T.; Rekola, R.; Sillanpää, A.; Takalo, L. O.; Teräsranta, H.; Tosti, G.; Balonek, T. J.; Feldt, M.; Heines, A.; Heisler, Charlene A.; Hu, Jingyao; Kidger, M.; Mattox, J. R.; McGrath, Elizabeth J.; Pati, A. K.; Robb, R. M.; Sadun, A. C.; Shastri, P.; Wagner, S. J.; Wei, J. Y.; Wu, Xue-Bing

doi:10.1051/0004-6361:20011112

Cited by 170 publications

(138 citation statements)

References 54 publications

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“…Rieger (2004) also attributes variability of blazars to differential Doppler boosting effects, as the plasma follows helical trajectories, induced by different possible mechanisms (as orbital motion of a BBH system, intrinsic jet rotation and jet precession). A geometrical origin (relativistic beaming) for the variability of blazar AO 0235+16 is also considered by Raiteri et al (2001).…”

Section: Correlation Between Kinematics and Flux-density Variabilitymentioning

confidence: 99%

Non-radial motion in the TeV blazar S5 0716+714

Britzen¹,

Kam²,

Witzel³

et al. 2009

A&A

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Context. Flat-spectrum radio sources often show a core-jet structure on pc-scales. Individual jet components reveal predominantly outward directed motion. For the BL Lac object S5 0716+714 conflicting apparent velocities have been reported in the literature. This object is an intra-day variable source and suited to investigate a possible correlation between kinematic properties and flux-density variability on different timescales. Aims. We study the kinematics in the pc-scale jet of S5 0716+714 to determine the apparent speeds of the jet components based on a much improved data set. In addition, we search for correlations between the radio flux-density light curves and the morphological changes detected along the VLBI jet. Methods. We (re-)analyze 50 VLBI observations obtained with the VLBA at 5 different frequencies (5-43 GHz) between 1992.73 and 2006.32. The data have been parameterized using circular Gaussian components. We analyze the jet component motion in detail taking care not only to account for motion in the radial but also in the orthogonal direction. We study the evolution of the jet ridge line and investigate the spectral properties of the individual components. We search for correlations between radio band light curves and the kinematic properties of the jet components. Results. We present an alternative kinematic scenario for jet component motion in S5 0716+714. We present evidence for the apparent stationarity of jet components (with regard to their core separation) with time. Jet components, however, do seem to move significantly non-radially with regard to their position angle and in a direction perpendicular to the major axis of the jet. We discuss a possible correlation between the long-term radio flux-density variability and apparent jet component motions. Conclusions. In S5 0716+714 an alternative motion scenario is proposed. With regard to the core separation, rather stationary components can fit the VLBI observations well. A new model to explain the observed motion with regard to the position angle is required. Based on the correlation between the longterm radio flux-density variability and the position angle evolution of a jet component, we conclude that a geometric contribution to the origin of the long-term variability might not be negligible. Subluminal motion has been reported for most of the TeV blazars. Our analysis also confirms this finding for the case of S5 0716+714. This result increases the number of TeV blazars showing apparent subluminal motion to 7.

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Section: Correlation Between Kinematics and Flux-density Variabilitymentioning

confidence: 99%

Non-radial motion in the TeV blazar S5 0716+714

Britzen¹,

Kam²,

Witzel³

et al. 2009

A&A

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“…In low resolution images, the modulation of the gas ejection appears in a radio flux density variability, which is observed in many objects. In particular there are several studies of radio light curves of single objects (e.g., Vicente et al 1996;Raiteri et al 2001) or of group of blazars (e.g., Venturi et al 2001). In latter works, it is possible to recognize a quasi-periodical variability of the sources, much more evident in the high-frequency light curves Teräsranta et al (2005).…”

Section: This Workmentioning

confidence: 99%

“…The production of such blobs is connected with flares in the strongly variable light curves (Perlman et al 2001). Generally, the radio light curves of AGN do not exhibit any periodicity, but the analysis of most time-extended radio light curves of some X and γ ray-loud blazars (Raiteri et al 2001;Venturi et al 2001) shows the signature of a longterm quasi-periodic behaviour. Some of the observed periodic variabilities may be explained by the helical-jet model (Königl & Choudhuri 1985;Camenzind & Krockenberg 1992;Raiteri et al 1999;Guerra 2004;Rieger 2004), but kinematic studies of parsec-scale radio jets have provided observational evidence for helical trajectories only in a few AGN showing periodicities (Vicente et al 1996;Tateyama et al 1998;Gomez et al 1999;Kellermann et al 2004).…”

Section: Introductionmentioning

confidence: 99%

The role of viscosity in AGN outflows in relation to jet periodicities

Lanzafame¹,

Cassaro

Schillirò

et al. 2008

A&A

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Aims. Adopting the Smoothed Particle Hydrodynamics (SPH) numerical method, we performed a grid of evolving models of a 3D axially-symmetric, viscous accretion disc around a supermassive black hole (SMBH) of 10 6 ÷ 10 9 M . Such sort of simulations are typical of accretion discs in active galactic nuclei (AGN). In such disc models, we pay attention to the role of the specific angular momentum λ and the turbulent viscosity parameter α, according to the Shakura and Sunyaev prescription. One or two shock fronts in the radial inviscid flow develop, according to the assigned initial kinematic and thermodynamic conditions. Methods. By fixing the initial and boundary conditions on the flow at the disc outer edge, where the total energy, the specific angular momentum λ, and the initial velocity are concerned, we find pairs of (α, λ) values determining radial periodical oscillations in the shock front. In some cases, an outflow develops from the subsonic post-shock region, close to the black hole. Results. The link between the accretion disc and the jet refueling through the onset of a centrifugal shock front is evident. We also compare model variability periods with observed ones in the radio light curves of AGN.

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“…Among other claims of optical, radio, or optical-radio regular oscillations of year timescale in blazars, we refer to the quasiperiodic radio-band behavior of BL Lac (∼8 yr, Villata et al 2004Villata et al , 2009) and the occurrence of major radio-optical outbursts in AO 0235+16 (∼5.7 yr or longer, Raiteri et al 2001Raiteri et al , 2006Raiteri et al , 2008 that are compatible with the optical light curves. A helical jet model that leads to changes in Doppler-boosted flux (Ostorero et al 2004) and driven by orbital motion in a BBHS was proposed for both the sources.…”

Section: Introductionmentioning

confidence: 99%

Gamma-ray and optical oscillations of 0716+714, MRK 421, and BL Lacertae

Sandrinelli

Covino

Treves

et al. 2017

A&A

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We examine the 2008-2016 γ-ray and optical light curves of three bright BL Lac objects, 0716+714, MRK 421, BL Lac, which exhibit large structured variability. We searched for periodicities by using a fully Bayesian approach. For two out of three sources investigated, no significant periodic variability was found. In the case of BL Lac, we detected a periodicity of ∼ 680 days. Although the signal related to this is modest, the coincidence of the periods in both gamma and optical bands is indicative of a physical relevance. Taking into consideration previous literature results, possibly related γ-ray and optical periodicities of about one year time scale are proposed in four bright γ-ray blazars out of the ten examined in detail. Compared with results from periodicity search of optical archives of quasars, the presence of quasi-periodicities in blazars may be more frequent by a large factor. This suggests the intriguing possibility that the basic conditions for their observability are related to the relativistic jet in the observer direction, but the overall picture remains uncertain.

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Optical and radio variability of the BL Lacertae object AO 0235+16: A possible 5-6 year periodicity

Cited by 170 publications

References 54 publications

Non-radial motion in the TeV blazar S5 0716+714

Non-radial motion in the TeV blazar S5 0716+714

The role of viscosity in AGN outflows in relation to jet periodicities

Gamma-ray and optical oscillations of 0716+714, MRK 421, and BL Lacertae

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