Correlated radio and optical variability in the BL Lacertae object 0716 + 714

Quirrenbach, A.; Witzel, A.; Wagner, S. J.; Sanchez-Pons, F.; Krichbaum, T. P.; Wegner, R.; Anton, K.; Erkens, U.; Haehnelt, Martin G.; Zensus, J. A.; Johnston, K. J.

doi:10.1086/186026

Cited by 173 publications

(157 citation statements)

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“…Apparently correlated optical/radio quasi-periods of ∼1 day lasting over several days have been observed by Quirrenbach et al (1991). Gupta et al (2008) report a rough period of ∼3.0 ± 0.3 years and Gupta et al (2009) find quasiperiodic oscillations (QPOs) of ∼30 min.…”

Section: Introductionmentioning

confidence: 91%

“…It is still the only active galactic nuclei (AGN) for which a simultaneous change in the mode of the radio/optical variability has been observed on intra-day time scales (Quirrenbach et al 1991) and is thus so far the best candidate for an intrinsic origin of intra-day variability (IDV, Wagner & Witzel 1995, and references therein).…”

Section: Introductionmentioning

confidence: 99%

“…Several authors claim the detection of periodicity or nearly periodic variations in radio and optical (Quirrenbach et al 1991), optical (Gupta et al 2008) and X-ray light-curves (Gupta et al 2009). Apparently correlated optical/radio quasi-periods of ∼1 day lasting over several days have been observed by Quirrenbach et al (1991).…”

Section: Introductionmentioning

confidence: 99%

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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: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

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

Britzen¹,

Kam²,

Witzel³

et al. 2009

A&A

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“…One of the most prominent sources displaying correlated variability at different wavelengths is 0716+714 (radio and optical) (Quirrenbach et al 1991;Wagner et al 1996). The source OJ287 is another famous example, that has correlated variability in the radio, optical, and infrared (see e.g., Fan & Lin 1999).…”

Section: Periodicities In the Lightcurvesmentioning

confidence: 99%

Tracing the merger-driven evolution of active galaxies using the CJF sample

Karouzos¹,

Britzen²,

Eckart

et al. 2010

A&A

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Context. For the evolution of large-scale structures in the Universe, it is unclear whether active galaxies represent a phase that each galaxy undergoes, and whether and to which extent the evolution of black holes at their centers is important. Binary black hole (BBH) systems may play a key role in our understanding of the above questions. Aims. We investigate the Caltech-Jodrell Bank flat-spectrum (CJF) sample to identify evidence that supports the merger-driven evolution scheme of active galaxies, and search for tracer-systems of active galactic nucleus (AGN) evolution and possible BBH candidates. We discuss the strength of and uncertainty in the evidence and formulate a set of selection criteria to detect such tracer-systems. Methods. We conduct an extensive literature search for all available multiwavelength data, particularly in the optical and infrared regime, and morphological information about the CJF sources. We perform a statistical analysis of the properties of this sample. Results. We find 1 ULIRG (Mrk 231) included in the CJF prototype of a transitory system. In total, 28.6% of the CJF sources with z ≤ 0.4 are distorted or have a companion. Given the unbiased sample used here, this provides strong evidence of the ubiquity of the merger phenomenon in the context of active galaxies. We find a correlation between the radio and the near-infrared luminosity of the high-luminosity sources, interpreted in the context of the interplay between a star-formation and AGN component. We find a connection between variability and evolutionary transitory systems, as selected on the basis of their near-infrared colors. We select 28 sources that trace the different evolution phases of an AGN, as well as a number of the most promising BBH candidates. We find 4 sources with almost periodical variability in the optical and radio on similar timescales.

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“…Ghisellini et al 1997;Raiteri et al 2003). Correlation between radio (at 5 GHz) and optical (at 650 nm) variability suggest that scintillation, a process that is not effective at high radio and optical frequencies, does not play a large part in the observed variability (Quirrenbach et al 1991;Wagner 2001). More recent multi-frequency studies of S5 0716+714 (e.g.…”

Section: The Bl Lac Object S5 0716+714mentioning

confidence: 99%

A synchrotron self-Compton model with low-energy electron cut-off for the blazar S5 0716+714

Tsang

Kirk

2007

A&A

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Context. In a self-absorbed synchrotron source with power-law electrons, rapid inverse Compton cooling sets in when the brightness temperature of the source reaches T B ∼ 10 12 K. However, brightness temperatures inferred from observations of intra-day variable sources (IDV) are well above the "Compton catastrophe" limit. This can be understood if the underlying electron distribution cuts off at low energy. Aims. We examine the compatibility of the synchrotron and inverse Compton emission of an electron distribution with low-energy cut-off with that of IDV sources, using the observed spectral energy distribution of S5 0716+714 as an example. Methods. We compute the synchrotron self-Compton (SSC) spectrum of monoenergetic electrons and compare it to the observed spectral energy distribution (SED) of S5 0716+714. The hard radio spectrum is well-fitted by this model, and the optical data can be accommodated by a power-law extension to the electron spectrum. We therefore examine the scenario of an injection of electrons, which is a double power law in energy, with a hard low-energy component that does not contribute to the synchrotron opacity. Results. We show that the double power-law injection model is in good agreement with the observed SED of S5 0716+714. For intrinsic variability, we find that a Doppler factor of D ≥ 30 can explain the observed SED provided that low-frequency (<32 GHz) emission originates from a larger region than the higher-frequency emission. To fit the entire spectrum, D ≥ 65 is needed. We find the constraint imposed by induced Compton scattering at high T B is insignificant in our model. Conclusions. We confirm that electron distribution with a low-energy cut-off can explain the high brightness temperature in compact radio sources. We show that synchrotron spectrum from such distributions naturally accounts for the observed hard radio continuum with a softer optical component, without the need for an inhomogeneous source. The required low energy electron distribution is compatible with a relativistic Maxwellian.

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Correlated radio and optical variability in the BL Lacertae object 0716 + 714

Cited by 173 publications

References 0 publications

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

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

Tracing the merger-driven evolution of active galaxies using the CJF sample

A synchrotron self-Compton model with low-energy electron cut-off for the blazar S5 0716+714

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