Search results for "RLU"

Does GRS 1915+105 exhibit "canonical" black-hole states?

2003

We have analysed RXTE data of the superluminal source GRS 1915+105 in order to investigate if, despite its extreme variability, it also exhibits the canonical source states that characterise other black-hole candidates. The phenomenology of GRS 1915+105 has been described in terms of three states (named A, B and C) based on their hardness ratios and position in the colour-colour diagram. We have investigated the connection between these states and the canonical behaviour and found that the shape of the power spectral continuum and the values of the best-fit model parameters to the noise components in all three states indicate that the source shows properties similar to the canonical very hi…

VSOP monitoring of the quasar 1928+738

2000

Abstract In the paper we describe the first results from a campaign to monitor the relatively low redshift (z=0.3) circumpolar superluminal quasar 1928+738 with VSOP. The three epochs of data that we have analyzed show that there have been substantial structural changes in this source near the core on the time-scale of a few months.

Jet stability and the generation of superluminal and stationary components

2001

We present a numerical simulation of the response of an expanding relativistic jet to the ejection of a superluminal component. The simulation has been performed with a relativistic time-dependent hydrodynamical code from which simulated radio maps are computed by integrating the transfer equations for synchrotron radiation. The interaction of the superluminal component with the underlying jet results in the formation of multiple conical shocks behind the main perturbation. These trailing components can be easily distinguished because they appear to be released from the primary superluminal component, instead of being ejected from the core. Their oblique nature should also result in distinc…

Radio-optical scrutiny of compact AGN: Correlations between properties of pc-scale jets and optical nuclear emission

2010

We study the correlations between the Very Long Baseline Array radio emission at 15 GHz, extended emission at 151 MHz, and optical nuclear emission at 5100 AA for a complete sample of 135 compact jets. We use the partial Kendall's tau correlation analysis to check the link between radio properties of parsec-scale jets and optical luminosities of host AGN. We find a significant positive correlation for 99 quasars between optical nuclear luminosities and total radio (VLBA) luminosities of unresolved cores at 15 GHz originated at milliarcseconds scales. For 18 BL Lacs, the optical continuum emission correlates with the radio emission of the jet at 15 GHz. We suggest that the radio and optical …

ERRATUM: “MOJAVE. X. PARSEC-SCALE JET ORIENTATION VARIATIONS AND SUPERLUMINAL MOTION IN ACTIVE GALACTIC NUCLEI” (2013, AJ, 146, 120)

2016

Simulations of Precessing Jets

2003

We report on the results of a three-dimensional, relativistic, hydrodynamical simulation of a precessing jet through which a compact blob of matter is set to propagate. We conclude that the morphology of superluminal sources is the result of a complex combination of phase motions, viewing angle selection effects, and non-linear interactions between perturbations and the underlying jet and/or external medium.

Subparsec Polarimetric Radio Observations of 3C 120: A Close‐up Look at Superluminal Motion

1998

We present two-epoch polarimetric images of the radio galaxy 3C 120 obtained with the Very Long Baseline Array at 22 and 43 GHz. Because of the proximity of 3C 120 (z = 0.033), the 43 GHz observations allow us to observe superluminal motions with the highest resolution achieved to date, 0.07 h-1 pc. Up to ten different superluminal components, with velocities between 2.3 and 5.4 h-1c, can be observed in this active source, with approximately monthly ejections of new components. Polarization is observed in several components and at both frequencies, with peaks in the linearly polarized flux not always coincident with the peaks in total intensity. The orientation of the magnetic field is obse…

Hydrodynamical and Emission Simulations of Relativistic Jets: Stability and Generation of Superluminal and Stationary Components

2001

We present 2D hydrodynamical and emission simulations of the jet stabilityafter the introduction of strong perturbations on a relativistic jet. These simulations show that the interaction of a single strong perturbation with the underlying jet results in the formation of multiple conical shocks with very specific observational properties.

Superluminal two-color light in multiple Raman gain medium

2014

We investigate theoretically the formation of two-component light with superluminal group velocity in a medium controlled by four Raman pump fields. In such an optical scheme only a particular combination of the probe fields is coupled to the matter and exhibits superluminal propagation, the orthogonal combination is uncoupled. The individual probe fields do not have a definite group velocity in the medium. Calculations demonstrate that this superluminal component experiences an envelope advancement in the medium with respect to the propagation in vacuum.

Changes in the trajectory of the radio jet in 0735+178?

2001

We present multi-epoch 8.4 and 43 GHz Very Long Baseline Array images of the BL Lac object 0735+178. The images confirm the presence of a twisted jet with two sharp apparent bends of 90$^{\circ}$ within two milliarcseconds of the core, resembling a helix in projection. The observed twisted geometry could be the result of precession of the jet inlet, but is more likely produced by pressure gradients in the external medium through which the jet propagates. Quasi-stationary components are observed at the locations of the 90$^{\circ}$ bends, possibly produced by differential Doppler boosting. Identification of components across epochs, since the earliest VLBI observations of this source in 1979…