Query : 2009A&A...508.1205B

2009A&A...508.1205B - Astronomy and Astrophysics, volume 508, 1205-1215 (2009/12-4)

Non-radial motion in the TeV blazar S5 0716+714. The pc-scale kinematics of a BL Lacertae object.


Abstract (from CDS):

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. 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. We (re-)analyze 50 VLBI observations obtained with the VLBA at 5 different frequencies (5-43GHz) 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. 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. 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.

Abstract Copyright:

Journal keyword(s): galaxies: active - BL Lacertae objects: individual: S5 0716+714 - techniques: interferometric

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 QSO B0235+1624 BLL 02 38 38.93010450 +16 36 59.2745528   16.46 15.50 15.92   ~ 1531 2
2 6C 035545+504923 Bla 03 59 29.74727351 +50 57 50.1618607           ~ 442 1
3 QSO J0530+13 Bla 05 30 56.41674741 +13 31 55.1494688     20.00 19.35   ~ 952 1
4 8C 0716+714 BLL 07 21 53.4482942664 +71 20 36.363846516   15.5 15.50 14.27   ~ 1283 1
5 QSO J0854+2006 BLL 08 54 48.8749846272 +20 06 30.639583620   15.91 15.43 15.56   ~ 2314 1
6 NAME Her B Sy1 16 42 58.80997043 +39 48 36.9939552   16.81 16.59 16.84   ~ 1711 2
7 8C 1803+784 BLL 18 00 45.6838528560 +78 28 04.018028016   16.4 15.90 15.46   ~ 732 1

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