A massive binary black hole in 1928 + 738?

Roos, Nico; Kaastra, J. S.; Hummel, Christian A.

doi:10.1086/172647

Cited by 115 publications

(116 citation statements)

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“…Furthermore, they propose that for strong enough magnetic fields, the K-H instabilities can be considered negligible. Roos et al (1993) argue that the orbital motion of the binary is responsible for the change of the jet-ejection direction and thus leads to a wiggling structure (the jet is treated ballistically). Kaastra & Roos (1991) argue that the precession angle is determined by the angle between the primary black hole spin axis and the angular momentum of the binary system.…”

Section: Models Relying On a Binary Black Holementioning

confidence: 99%

The kinematics in the pc-scale jets of AGN

Britzen¹,

Kudryavtseva

Witzel³

et al. 2010

A&A

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Context. BL Lac objects show core-jet structures with features moving outwards along the jet. We present a kinematic analysis of jet component motion in the pc-scale jet of the BL Lac object S5 1803+784, which does not reveal long-term outward motion for most of the components. Aims. S5 1803+784 shows complex kinematic phenomena; understanding these provides new insights into the emission processes in BL Lac objects and possibly into the differences between quasars and BL Lac objects. Methods. The blazar S5 1803+784 has been studied with VLBI at ν = 1.6, 2. 3, 5, 8.4, and 15 GHz between 1993.88 and 2005.68 in 26 observing runs. We (re)analyzed the data and present Gaussian model-fits. We collected the already published kinematic information for this source from the literature and re-identified the components according to the new scenario presented in this paper. Altogether, 94 epochs of observations have been investigated. Results. A careful study of the long-term kinematics reveals a new picture for jet component motion in S5 1803+784. In contrast to previously discussed motion scenarios, we find that the jet structure within 12 mas of the core can most easily be described by the coexistence of several bright jet features that remain on the long-term at roughly constant core separations (in addition to the already known "stationary" jet component ∼1.4 mas) and one faint component moving with an apparent superluminal speed (∼19c, based on 3 epochs). While most of the components maintain long-term roughly constant distances from the core, we observe significant, smooth changes in their position angles. We report on an evolution of the whole jet ridge line with time over the almost 12 years of observations. The width of the jet changes periodically with a period of ∼8−9 years. We find a correlation between changes in the position angle and maxima in the total flux-density light-curves. We present evidence for a geometric origin of the observed phenomena and discuss possible models. Conclusions. We find evidence for a significantly different scenario of jet component motion in S5 1803+784 compared to the generally accepted one of outwardly moving jet components, and conclude that the observed phenomena (evolution of the jet ridge line, roughly constant component core separations but with significant position angle changes) can most easily be explained within a geometric model.

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Section: Models Relying On a Binary Black Holementioning

confidence: 99%

The kinematics in the pc-scale jets of AGN

Britzen¹,

Kudryavtseva

Witzel³

et al. 2010

A&A

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show abstract

“…SMBH), precession can occur as a result of the Bardeen-Petterson effect (Caproni et al 2006), magnetic torques (Lai 2003) or magnetohydrodynamic instabilities, prominently Kelvin-Helmholtz instabilities (e.g., Camenzind & Krockenberger 1992; Hardee & Norman 1988;Birkinshaw 1991;Zhao et al 1992;Hardee et al 1994;Hardee et al 1997;Meier & Nakamura 2006;Perucho et al 2006). If we assume that the AGN core hosts a binary system (presumably a binary black hole, BBH) then precession can occur as a result of the orbital motion of the binary system (e.g., Lobanov & Roland 2005;Roos et al 1993;Kaastra & Roos 1992), tidal forces, gravitational torques (e.g., Katz 1997;Romero et al 2000), as well as orbital motion of the system around the galactic gravity center (Roland et al 2008). …”

Section: Apparent Stationarity and Non-radial Motion Of Jet Componentsmentioning

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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“….12. QSO 1928+738 (4C 73.18) QSO 1928+738 has V = 15.5 and z = 0.3021 (Roos et al 1993), and displays superluminal motion in a jet oriented westwards. It is the best known and most extensively studied radio source of the complete S5 polar cap sample.…”

Section: Bl 1803+784mentioning

confidence: 99%

“…Eckart et al (1985) reported a self-absorbed core and a pc-scale jet 17 mas long, whose components display superluminal motion. Roos et al (1993) modeled the radio source as a binary black hole. Guirado et al ( , 1998 detected a shift in the peak of brightness between different epochs, based on an astrometric analysis.…”

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confidence: 99%

Absolute kinematics of radio source components in the complete S5 polar cap sample

Ros

Marcaide

Guirado

2001

A&A

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Abstract. We observed the thirteen extragalactic radio sources of the S5 polar cap sample at 8.4 GHz with the Very Long Baseline Array, on 1997.93 and 1999.41. We present the maps from those two epochs and briefly discuss the morphological changes experimented by some of the radio sources in the 1.4 yr elapsed. These results correspond to the first two epochs at 8.4 GHz of a program directed to study the absolute kinematics of the radio source components of the members of the sample by means of phase delay astrometry at 8.4, 15 and 43 GHz.

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A massive binary black hole in 1928 + 738?

Cited by 115 publications

References 0 publications

The kinematics in the pc-scale jets of AGN

The kinematics in the pc-scale jets of AGN

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

Absolute kinematics of radio source components in the complete S5 polar cap sample

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