Apparent Superluminal Speeds Research Articles

Interactions between the Jet and Disk Wind in Nearby Radio-intermediate Quasar III Zw 2

Disk winds and jets are ubiquitous in active galactic nuclei (AGN), and how these two components interact remains an open question. We study the radio properties of the radio-intermediate quasar III Zw 2. We detect two jet knots, J1 and J2, on parsec scales that move at a mildly apparent superluminal speed of 1.35c. Two γ-ray flares were detected in III Zw 2 in 2009–2010, corresponding to the primary radio flare in late 2009 and the secondary radio flare in early 2010. The primary 2009 flare was found to be associated with the ejection of J2. The secondary 2010 flare occurred at a distance of ∼0.3 pc from the central engine, probably resulting from the collision of the jet with the accretion disk wind. The variability characteristics of III Zw 2 (periodic radio flares, unstable periodicity, multiple quasiperiodic signals and the possible harmonic relations between them) can be explained by the global instabilities of the accretion disk. These instabilities originating from the outer part of the warped disk propagate inward and can lead to modulation of the accretion rate and consequent jet ejection. At the same time, the wobbling of the outer disk may also lead to oscillations of the boundary between the disk wind and the jet tunnel, resulting in changes in the jet–wind collision site. Object III Zw 2 is one of the few cases observed with jet–wind interactions, and the study in this paper is of general interest for gaining insight into the dynamic processes in the nuclear regions of AGN.

Constraining the radio jet proper motion of the high-redshift quasar J2134−0419 at z = 4.3

To date, PMN J2134-0419 (at a redshift z=4.33) is the second most distant quasar known with a milliarcsecond-scale morphology permitting direct estimates of the jet proper motion. Based on two-epoch observations, we constrained its radio jet proper motion using the very long baseline interferometry (VLBI) technique. The observations were conducted with the European VLBI Network (EVN) at 5 GHz on 1999 November 26 and 2015 October 6. We imaged the central 10-pc scale radio jet emission and modeled its brightness distribution. By identifying a jet component at both epochs separated by 15.86 yr, a proper motion of mu=0.035 +- 0.023 mas/yr is found. It corresponds to an apparent superluminal speed of beta_a=4.1 +- 2.7 c . Relativistic beaming at both epochs suggests that the jet viewing angle with respect to the line of sight is smaller than 20 deg, with a minimum bulk Lorentz factor Gamma=4.3. The small value of the proper motion is in good agreement with the expectations from the cosmological interpretation of the redshift and the current cosmological model. Additionally we analyzed archival Very Large Array observations of J2143-0419 and found indication of a bent jet extending to ~30 kpc.

APPARENT INWARD MOTION OF THE PARSEC-SCALE JET IN THE BL LAC OBJECT OJ287 DURING THE 2011-2012 γ-ray FLARES

We present a kinematic study of the parsec-scale radio jet in OJ 287, one of the most studied BL Lac objects, during γ-ray flares, to explore the relation between parsec-scale radio jet activity and γ-ray emission. The 22-GHz light curve of OJ 287 show three obvious flare events around 2011 May, 2011 October, and 2012 March. The second radio flare occurred during the γ-ray flaring period, and the third radio flare seemed to precede the γ-ray flare by one month. One jet component moved outward with respect to the core component with an apparent superluminal speed (~ 11c) from 2010 November to 2011 November. Then it changed direction, moving apparently inward in 2011 November, when the γ-ray flare occurred. The observed apparent inward motion of the jet at 22 GHz could be caused by a new jet component, unresolved at 22 GHz, in the innermost region.

Population statistics of beamed sources – I. A new model for blazars

Observations of blazar jets are shrouded in relativistic effects, thus hindering our understanding of their intrinsic properties and dominant physical processes responsible for their generation, evolution,radiation and particle emission. In this work we focus on extracting information about timescales in the jet rest frame using a population-modeling approach. We employ Monte Carlo simulations to derive a simple population model for the intrinsic unbeamed luminosities and the Lorentz $\Gamma$ of blazar jets that adequately describe the observed redshift and apparent superluminal speed distributions for flux-limited blazar samples. We derive separate models for BL Lacs and Flat Spectrum Radio Quasars. We then use these models to compute the predicted distribution of Doppler factors in each blazar class, and address the following questions: (a) What is the relativistically induced spread in observed timescales (e.g., event duration, time lags) in a flux-limited sample of relativistic jets? (b) Could differences between BL Lacs and FSRQs observed in the time domain be attributed to differences in beaming between the two populations? (c) Is there a statistically preferred amount of beaming in a flux-limited sample? How large are statistical deviations from that preferred value? We use our findings to propose promising approaches in phenomenological studies of timescales in blazar jets.

Apparent Superluminal Speeds in Evanescent Fields, Quantum Tunnelling and Quantum Entanglement

Three cases of wave propagation involving possible superluminal speeds are discussed. The picture that emerges is that the actual propagation velocity of the wave front never exceeds the speed of light in vacuum. However, once the wave front has reached some distant point in space, then propagation may actually seem to take place along this wave with superluminal speed, yet involving no conflict with special relativity. Quantum entanglement – Einstein’s “spooky action at a distance” – is one famous, and now experimentally verified example of propagation at such apparent superluminal speed, but which is here explained within the framework of special relativity. This then at the same time also leads to a deeper understanding of the limitation of the recently proposed clock-hypothesis in special relativity, and also provides an illustration of the mechanism involved in wave-particle duality.

Kinematic study of the parsec-scale jet of the quasar PKS 1741–03

We present 23 interferometric images of parsec-scale jet of the quasar PKS 1741--03 at 15, 24 and 43 GHz spanning about 13 yr. We model the images as a superposition of discrete two--dimensional elliptical Gaussian components, with parameters determined by the cross--entropy technique. All the images present a spatially unresolved component (core) and usually two or three components receding from it. The same components were found in simultaneous 24 and 43 GHz maps, showing the robustness of our model-fitting. The core-shift opacity effect between these frequencies is weak. We have identified seven components moving along straight lines at constant apparent superluminal speeds ($3.5\le\beta_\mathrm{obs}\le 6.1$), with different sky position angles ($-186\deg\le \eta\le -125\deg$). The core flux density tracks quite well the fluctuations seen in the historical single-dish light curve at 14.5 GHz, with no measurable delay. The total flux density from the moving jet components is delayed $\sim$2 yr in relation to the core light curve, roughly the same as the lag between the ejection epoch and the maximum flux density in the light curves of the jet components. We propose that there are three non-exclusive mechanisms for producing these delays. From the kinematics of the most robust jet components and the core brightness temperature, we determined the bulk Lorentz factor ($4.8\le\gamma\le 24.5$) and the jet viewing angle ($0.\deg 35 \le \theta \le 4.\deg 2$); these values agree with previous estimates from the spectral energy distribution of PKS 1741--03 and its radio variability.

On the Extended Lorentz Transformation Model and Its Application to Superluminal Neutrinos

In this paper, we consider the apparent superluminal speed of neutrinos in their travel from CERN to Gran Susso, as measured by the OPERA experiment, within the framework of the Extended Lorentz Transformation Model. The model is based on a natural extension of Lorentz transformation by wick rotation. Scalar and Dirac’s fields are considered and invariance under the new lorentz group is discussed. Moreover, an extension of quantum mechanics to accommodate new particles is considered using the newly proposed Generalized-C quantum mechanics. A two dimensional representation of the new Dirac’s equation is therefore formulated and its solution is calculated.

The kinematics in the pc-scale jets of AGN

We present a kinematic analysis of jet component motion in the VLBI jet of the BL Lac object S5 1803+784, which does not reveal long-term outward motion for most of the components. Understanding the complex kinematic phenomena can possibly provide insights into the differences between quasars and BL Lac objects. The blazar S5 1803+784 has been studied with VLBI at $\nu$ =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. A careful study of the long-term kinematics reveals a new picture for 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 {\it stationary} jet component $\sim$ 1.4 mas) and one faint component moving with an apparent superluminal speed ($\sim$ 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 $\sim$ 8 to 9 years. We find a correlation between changes in the position angle and maxima in the total flux-density. We present evidence for a geometric origin of the phenomena and discuss possible models.

Multi-frequency VLBA study of the blazar S5 0716+714 during the active state in 2004

We observed the blazar 0716+714 with the VLBA during its active state in 2003–2004. In this paper we discuss multi-frequency analysis of the inner jet (first 1 mas) kinematics. The unprecedentedly dense time sampling allows us to trace jet components without misidentification and to calculate the component speeds with good accuracy. In the smooth superluminal jet we were able to identify and track three components over time moving outwards with relatively high apparent superluminal speeds (8.5–19.4c), which contradicts the hypothesis of a stationary oscillating jet in this source. Component ejections occur at a relatively high rate (once in two months), and they are accompanied by mm-continuum outbursts. Superluminal jet components move along wiggling trajectories, which is an indication of actual helical motion. Fast proper motion and rapid decay of the components suggest that this source should be observed with the VLBI at a rate of at least once in one or two months in order to trace superluminal jet components without confusion.

The Parsec-Scale Jet of PKS 0637−752

Abstract Chandra observations of the quasar PKS 0637$-$752 during its checkout phase resulted in the unexpected detection of a luminous kiloparsec-scale X-ray jet. The apparent superluminal speed of this jet on the parsec-scale, based on two VSOP and four ground-based observations, has proven crucial to understanding the X-ray production in the arcsec-scale jet. We present here for the first time the full details of the ground-based observations used to determine the parsec-scale jet speed, describe the results of a third VSOP observation, and examine the reported jet speed in the light of more recent ground-based VLBI observations. We find some evidence of increased source activity coincident with extrapolated epochs of jet component ejection, although the monitoring of the source is relatively sparse and the ejection epochs are not tightly constrained. We also construct the spectral energy distribution for the nucleus of PKS 0637$-$752 and show that it can be modelled well in terms of a one-zone synchrotron self-Compton model of an electron-positron jet with a Doppler factor of $\sim 10$, consistent with the results of the VLBI observations.

X‐ray and radio emission in the nuclei of radio galaxies and thedisk‐jet connection

AbstractIt appears that relativistic jets are produced by accreting black holes. We might therefore expect that events observed in jets, such as the appearance of bright radio knots moving at apparent superluminal speeds, originate as disturbances in the central engine. This is observed in a number of compact X‐ray binary systems in our Galaxy, manifested as changes in the X‐ray emission state followed by superluminal ejections. The author and collaborators have detected somewhat similar events in the radio galaxies 3C 120 (type Fanaroff‐Riley I) and 3C 111 (FR II). The data both confirm the disk‐jet connection in accreting supermassive black holes and provide constraints on the structure of the jet between the central engine and the millimeter‐wave core. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The implications of helical patterns in 3C 120

Ongoing monitoring observations of the 3C 120 radio jet with the VLBA at 1.7 GHz show a pattern and motions that suggest that the internal jet structure is helical with a long wavelength [ApJ 556 (2001) 772]. The pattern is stationary or slowly moving with features moving through it at apparent superluminal speeds. Physical theory and numerical simulation of jets show that the helical patterns are an expected result in many circumstances as a result of perturbations to the jet such as jet-cloud collision or precession. The wavelength and pattern speed of such structures are related to the internal sound speed and Lorentz factor and to the external sound speed. The internal jet structure expected from the theory suggests that the pattern will have a wider opening angle than the trajectories of individual particles. This helps avoid a requirement for extreme conditions when interpreting the appearance of the jet in terms of relativistic beaming.

Space VLBI observations of southern hemisphere gamma-ray and non-gamma-ray AGN: First results for PKS 0637-752

Abstract We present the first results from our VSOP proposal, “γ-ray loud and quiet AGN with VSOP and SHEVE at 5 GHz”. This project is aimed at determining what, if anything, differentiates γ-ray-identified radio sources from similar strong, flat-spectrum radio sources which have not been identified as sources of greater than 100 MeV γ-rays. Five VSOP observations have been successfully completed as part of this project during VSOP AO1. One observation has been correlated thus far, a 4.970 GHz observation of PKS 0637-752 from 1997 November 21. We present the VSOP image for PKS 0637-752 and make comparisons between the space VLBI image and ground-based VLBI and Australia Telescope Compact Array (ATCA) images, as well as present ATCA flux density monitoring at 4.8 GHz. A brightness temperature for PKS 0637-752 of 0.7 × 1012 K has been determined from the VSOP data and a tentative apparent superluminal speed, from comparison to the ground-based VLBI image, of ∼9c.

VLBI Observations of the Gamma‐Ray Blazar 1611+343

As part of an effort to observe high-energy γ-ray blazars with VLBI, we have produced 8 and 2 GHz VLBI images, at eight epochs, of the quasar 1611+343, which has been detected by the EGRET telescope on board the Compton Gamma Ray Observatory. The VLBI data have been taken from the geodetic database of the Washington VLBI correlator. As is expected for a γ-ray quasar, we find that 1611+343 possesses a jet with several compact components moving at apparent superluminal speeds. We have detected five components and have measured speeds for the outer four of 6.7 ± 1.6, 3.8 ± 1.4, 7.6 ± 1.3, and 11.5 ± 2.3 h-1c from the outermost component inward. (H0 = 100 h km s-1 Mpc-1, q0 = 0.5.) By comparing the apparent superluminal expansion speeds with a lower limit to the Doppler beaming factor derived from X-ray observations, we have calculated an upper limit on the angle of the jet to the line of sight of θ ≤ 68 and a lower limit to the Lorentz factor of the components of Γ ≥ 7.1. We have mapped the two-dimensional projected structure of the VLBI jet and clearly see different trajectories for different components at the same distance from the core, which rules out a continuous jet model for this source. A possible connection is found between enhanced levels of γ-ray activity and the ejection of new VLBI components from the core.

Physics of the M87 Jet

Motivated by the recent determination of proper motions of knots in the M87 jet by Biretta, Zhou, & Owen (1995), we have investigated the relationship between the dynamics of the jet and the kpc-scale radio and optical structure. We interpret the knots as internal shocks in the jet, and find that relativistic effects play an important role in their appearance. In particular, knot A, which appears to be almost transverse to the flow and seems to be viewed nearly edge-on, is in fact a highly oblique shock. The direction of its normal with respect to the flow lies within about 10° of the Mach angle, i.e., the angle of obliquity beyond which no shock is possible. In a frame comoving with the shock front, the incident streamlines make an angle of about 40° – 60° with respect to the shock normal. Knot A has a proper motion corresponding to only 0.51c, and the relativistic effects are modest. Its edge-on appearance is largely fortuitous. We have found, however, that relativistic effects would create a strong bias for shocks with apparent superluminal speeds to appear nearly edge-on.

Non-radial ejection in 3C345

The radio source 3C345 is associated with a 16th magnitude quasar with z = 0.595 (ref. 1). At radio wavelengths it has six major components. From largest to smallest these are: a low brightness halo2; a 3 kpc curved jet3; three steep-spectrum components (C1, C2, and C3) which define a curved jet4,5; and a compact component D which is self-absorbed at frequencies up to at least 10 GHz. Components C2 and C3 show proper motion relative to D at an apparent superluminal speed. We present VLBI observations at 10.7 GHz which show that a new radio component C4 has appeared and is moving along a non-radial path. This behaviour is consistent with the hypothesis that bending causes the jet curvature. We interpret our observations in light of the relativistic beam model6 as this is currently the most attractive explanation for both the superluminal effect and the weak X-ray emission4.