Kinematics of the parsec-scale jet of the blazar AO 0235+164

2019 ◽  
Vol 15 (S359) ◽  
pp. 345-346
Author(s):  
Flávio Benevenuto da Silva Junior ◽  
Anderson Caproni
Keyword(s):  
Structural Characteristics ◽  
Position Angle ◽  
Lorentz Factor ◽  
Merit Function ◽  
Cross Entropy ◽  
Optimum Number ◽  
Viewing Angle ◽  
Core Component ◽  
Upper Limit ◽  
Distance Position

AbstractRadio interferometric maps of the blazar AO 0235+164 show the existence of a stationary core, and a compact jet composed of multiple receding components. In this work, we determined the structural characteristics of these jet components (core-component distance, position angle, flux density, etc.) using the statistical method for global optimization Cross-Entropy (CE). The images we analyzed were extracted from public databases, totaling 41 images at 15 GHz and 128 images at 43 GHz. Using criteria such as the value of the CE merit function, and mean residuals, we determined the optimum number of components in each map analyzed in this work. We found that jet components are distributed across all four quadrants on the plane of the sky, indicating a possible non-fixed jet orientation during the monitoring interval. The time evolution of the equatorial coordinates of the jet components were used to determine their respective speeds, ejection epochs, and mean position angles on the plane of the sky. We have identified more than 20 components in the jet of AO 0235+164, with their apparent speeds ranging roughly from 2c to 40c, and distributed across all four quadrants on the plane of the sky. From the kinematics of these jet components we could derive a lower limit of about 39 for its bulk jet Lorentz factor and an upper limit of approximately 42 degrees for its jet viewing angle.

scholarly journals Kinematic signatures of triaxial stellar systems

1993 ◽  
Vol 153 ◽  
pp. 407-408
Author(s):  
Richard Arnold ◽  
Tim De Zeeuw ◽  
Chris Hunter
Keyword(s):  
Velocity Field ◽  
Dynamic Models ◽  
Elliptical Galaxies ◽  
Velocity Fields ◽  
Stellar Systems ◽  
Viewing Angle ◽  
Upper Limit ◽  
Wide Range ◽  
Triaxial Stellar Systems ◽  
Kinematic Models

Analytic dynamic models of triaxial stellar systems, such as elliptical galaxies and galactic bulges, can be used to calculate the velocity fields of systems in a wide range of potentials without the need for orbit integrations. We present results from a first application of these models, in the form of velocity fields projected onto the sky. The appearance of the velocity field depends strongly on the viewing angle. Thin orbit models provide a theoretical upper limit to streaming in all possible kinematic models in a given potential.

scholarly journals Jet-disk connection in OJ287

2010 ◽  
Vol 6 (S275) ◽  
pp. 275-279
Author(s):  
Mauri J. Valtonen ◽  
Tuomas Savolainen ◽  
Kaj Wiik
Keyword(s):  
Black Hole ◽  
Time Lag ◽  
Zero Point ◽  
Position Angle ◽  
Viewing Angle ◽  
The Past ◽  
Basic Model ◽  
Optical Light Curve ◽  
The Mean ◽  
Free Parameters

AbstractA model for OJ 287 consisting of two orbiting black holes has been constructed using optical light curve data. The model has successfully predicted the occurrence of sharp optical outbursts of OJ 287 for the past 15 years. Here we test if also the variations in the radio jet position angle can be explained within the framework of this same model, which has most of its parameters fixed by the timing of the optical flares. The model applied here has only three free parameters left, the (trivial) zero point of the jet position angle, the time lag between changes in the disk and jet orientations, and the zero point of the viewing angle. Despite its simplicity and the small number of free parameters, the model appears to be able to reproduce the main properties of the observed position angle variations during the past 30 years. The best fits are obtained when the time lag is either ~4 or ~14 years. However, the jet orientation seems to be unrelated to the direction of the spin of the primary black hole. This implies, assuming that the basic model is correct, that the mean orientation of the jet is determined by the orientation of the inner accretion disk, not by the spin axis of the black hole.

scholarly journals Searching for Hα emitting sources around MWC 758

2018 ◽  
Vol 613 ◽  
pp. L5 ◽  
Author(s):  
N. Huélamo ◽  
G. Chauvin ◽  
H. M. Schmid ◽  
S. P. Quanz ◽  
E. Whelan ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Mass Range ◽  
Position Angle ◽  
Central Star ◽  
Young Star ◽  
Upper Limit ◽  
T Tauri ◽  
Very Large Telescope ◽  
Accretion Rates ◽  
Differential Imaging

Context. MWC 758 is a young star surrounded by a transitional disk. The disk shows an inner cavity and spiral arms that could be caused by the presence of protoplanets. Recently, a protoplanet candidate has been detected around MWC 758 through high-resolution L′-band observations. The candidate is located inside the disk cavity at a separation of ~111 mas from the central star, and at an average position angle of ~165.5°. Aims. We aim at detecting accreting protoplanet candidates within the disk of MWC 758 through angular spectral differential imaging (ASDI) observations in the optical regime. In particular, we explore the emission at the position of the detected planet candidate. Methods. We have performed simultaneous adaptive optics observations in the Hα line and the adjacent continuum using SPHERE/ZIMPOL at the Very Large Telescope (VLT). Results. The data analysis does not reveal any Hα signal around the target. The derived contrast curve in the B_Ha filter allows us to derive a 5σ upper limit of ~7.6 mag at 111 mas, the separation of the previously detected planet candidate. This contrast translates into a Hα line luminosity of LHα ≲ 5×10−5 L⊙ at 111 mas. Assuming that LHα scales with Lacc as in classical T Tauri stars (CTTSs) as a first approximation, we can estimate an accretion luminosity of Lacc < 3.7 × 10−4 L⊙ for the protoplanet candidate. For the predicted mass range of MWC 758b, 0.5–5 MJup, this implies accretion rates smaller than Ṁ < 3.4 × (10−8−10−9)M⊙ yr−1, for an average planet radius of 1.1 RJup. Therefore, our estimates are consistent with the predictions of accreting circumplanetary accretion models for Rin = 1RJup. The ZIMPOL line luminosity is consistent with the Hα upper limit predicted by these models for truncation radii ≲3.2 RJup. Conclusions. The non-detection of any Hα emitting source in the ZIMPOL images does not allow us to unveil the nature of the L′ detected source. Either it is a protoplanet candidate or a disk asymmetry.

scholarly journals The Brightness and Polarization Structure of Compact Radio Sources

1988 ◽  
Vol 129 ◽  
pp. 161-162
Author(s):  
Raymond Rusk
Keyword(s):  
Position Angle ◽  
Active Galaxies ◽  
Radio Sources ◽  
Optical Polarization ◽  
Polarization Data ◽  
Core Component ◽  
Structural Position ◽  
Bl Lac Objects ◽  
The Core ◽  
Bl Lac

New VLA polarization data for 140 radio sources have been used to study the correlation between VLBI structural position angle and radio and optical polarization position angles reported in Rusk and Seaquist (1985). We confirm that there is a strong tendency, in active galaxies and quasars, for the radio E vector (of the core component) to lie normal to the VLBI structural axis. However, in BL Lac objects we find a tendency for the core radio E vector to be aligned parallel to the VLBI structural axis.

scholarly journals Determining the Lorentz Factor and Viewing Angle of GRB 170817A

2017 ◽  
Vol 852 (1) ◽  
pp. L1 ◽  
Author(s):  
Yuan-Chuan Zou ◽  
Fei-Fei Wang ◽  
Reetanjali Moharana ◽  
Bin Liao ◽  
Wei Chen ◽  
...  
Keyword(s):  
Lorentz Factor ◽  
Viewing Angle

scholarly journals Simulations of the radio polarization of a precessing pulsar PSR J1906+0746

2020 ◽  
Vol 497 (3) ◽  
pp. 2831-2838
Author(s):  
A K Galishnikova ◽  
A A Philippov ◽  
V S Beskin
Keyword(s):  
Wave Propagation ◽  
Radio Wave ◽  
Position Angle ◽  
Lorentz Factor ◽  
Radio Wave Propagation ◽  
Pulsar Magnetosphere ◽  
Plasma Parameters ◽  
Pair Plasma ◽  
General Aspects ◽  
Magnetic Poles

ABSTRACT The recently constructed theory of radio wave propagation in the pulsar magnetosphere outlines the general aspects of the radio light curve and polarization formation. It allows us to describe general properties of mean profiles, such as the position angle of the linear polarization, and the circular polarization for the realistic structure of the pair creation region in the pulsar magnetosphere. In this work, we present an application of the radio wave propagation theory to the radio observations of pulsar PSR J1906+0746. This pulsar is particularly interesting because observations of relativistic spin precession in a binary system allow us to put strong constraints on its geometry. Because it is an almost orthogonal rotator, the pulsar allows us to observe both magnetic poles; as we show, this is crucial for testing the theory of radio wave propagation and obtaining constraints on the parameters of magnetospheric plasma. Our results show that plasma parameters are qualitatively consistent with theories of pair plasma production in polar cap discharges. Specifically, for PSR J1906+0746, we constrain the plasma multiplicity λ ∼ 103 and the Lorentz factor of secondary plasma γ ∼ a few hundred.

Doppler factor, Lorentz factor and viewing angle of superluminal quasars

2013 ◽  
Vol 348 (1) ◽  
pp. 193-198 ◽  
Author(s):  
C. C. Onuchukwu ◽  
A. A. Ubachukwu
Keyword(s):  
Lorentz Factor ◽  
Viewing Angle ◽  
Doppler Factor

scholarly journals Viewing Angle and the Appearance of Superluminal Jets

1996 ◽  
Vol 175 ◽  
pp. 437-438
Author(s):  
H. D. Aller ◽  
M. F. Aller ◽  
P. A. Hughes ◽  
A. Mioduszewski
Keyword(s):  
Flow Pattern ◽  
Time History ◽  
Lorentz Factor ◽  
Helical Flow ◽  
Line Of Sight ◽  
Viewing Angle ◽  
Density Data ◽  
Bl Lacertae ◽  
Relativistic Flow ◽  
History Of

The time history of BL Lacertae has shown clear evidence of changes in jet orientation both in the plane of the sky and in the angle to the line of sight (see Figure 1). Models based on transverse shocks in a relativistic flow quantitatively fit the polarization and flux density data well and permit one to determine parameters of the flow such as the bulk Lorentz factor and the angle of the flow to the line of sight (Hughes, Aller and Aller 1989). The orientation of the jet flow to the line of sight changed by approximately 6° between the early 1980 bursts and one in 1991. There have been comparable changes in the orientation of the jet on the plane of the sky. Such changes in jet orientation may be due to a helical flow pattern arising from precession or instability.

scholarly journals Multi-Epoch Observations of Survey Sources

1984 ◽  
Vol 110 ◽  
pp. 131-134
Author(s):  
A.C.S. Readhead ◽  
T. J. Pearson ◽  
S. C. Unwin
Keyword(s):  
Structural Variations ◽  
Core Component ◽  
Upper Limit ◽  
5 Ghz

Five objects mapped as part of a VLBI survey have been re-observed at 5 GHz, and four of them have also been observed at 10 GHz. Three of the objects show no substantial structural variations: an upper limit of 2c can be placed on the apparent relative velocities of the components. One object (0711+356) shows structural variations which are mostly simply described in terms of a superluminal contraction. The remaining object (3C371, 1807+698) shows substantial structural variations which suggest that it probably is a superluminal source. The source 0710+439 is especially interesting as it consists of a central flat-spectrum core component straddled by two compact steep-spectrum components.

scholarly journals Parsec-scale properties of the radio brightest jetted AGN at z > 6

2020 ◽  
Vol 643 ◽  
pp. L12
Author(s):  
C. Spingola ◽  
D. Dallacasa ◽  
S. Belladitta ◽  
A. Caccianiga ◽  
M. Giroletti ◽  
...  
Keyword(s):  
Lorentz Factor ◽  
Physical Parameters ◽  
Viewing Angle ◽  
Microwave Background ◽  
Very Large Array ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Long Baseline ◽  
Scale Properties ◽  
Very Long Baseline Array

We present Director’s Discretionary Time multi-frequency observations obtained with the Jansky Very Large Array and the Very Long Baseline Array (VLBA) of the blazar PSO J030947.49+271757.31 (hereafter PSO J0309+27) at z = 6.10 ± 0.03. The milliarcsecond angular resolution of our VLBA observations at 1.5, 5, and 8.4 GHz unveils a bright one-sided jet extended for ∼500 parsecs in projection. This high-z radio-loud active galactic nucleus is resolved into multiple compact sub-components that are embedded in a more diffuse and faint radio emission that enshrouds them in a continuous jet structure. We directly derive limits on some physical parameters from observable quantities such as viewing angle and Lorentz and Doppler factors. If PSO J0309+27 is a genuine blazar, as suggested by its X-ray properties, then we find that its bulk Lorentz factor must be relatively low (lower than 5). This value would be in favour of a scenario currently proposed to reconcile the paucity of high-z blazars with current predictions. Nevertheless, we cannot exclude that PSO J0309+27 is seen under a larger viewing angle, which would imply that the X-ray emission must be enhanced, for example, by inverse Compton scattering with the cosmic microwave background. More stringent constraints on the bulk Lorentz factor in PSO J0309+27 and on these factors in the other high-z blazars are necessary to test whether their properties are intrinsically different from those of the low-z blazar population.

Sign in / Sign up

Export Citation Format

Share Document