Multi-frequency VLBI observations of NRAO 530

Feng, Shiwei; Shen, Zhi-Qiang; Cai, H.-B.; Chen, X.; Lu, R.-S.; Huang, Lei

doi:10.1051/0004-6361:20054678

Cited by 15 publications

(28 citation statements)

References 23 publications

(20 reference statements)

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“…In our analysis, we identify the southernmost component (component c) to be the stationary core of the radio emission, because of its flat radio spectrum (see ) and high compactness (see Table 2). This is in agreement with the identification scheme proposed by Jorstad et al (2001), Feng et al (2006) and Chen, Shen & Feng (2010).…”

Section: Resultssupporting

confidence: 92%

“…Our new images in 2007 reveal a jet structure for the inner region very different from those previously reported (e.g. in Feng et al 2006). NRAO 530 has undergone two moderate flares (Aller, Aller & Hughes 2009; Jenness, Robson & Stevens 2010) since the dramatic flare around 1997 (Bower et al 1997; Feng et al 2006).…”

Section: Introductioncontrasting

confidence: 90%

“…A comparison of the projected trajectories of jet components in 2007 and 1997 (Feng et al 2006) indicated that the morphology of the jet changed significantly. It is obvious that the major differences are in the regions close to the core, in contrast to the relative ‘position’ stationarity of the outermost component.…”

Section: Resultsmentioning

confidence: 99%

“…Space VLBI observations revealed brightness temperatures of NRAO 530 significantly in excess of both, the inverse Compton and the equipartition limit (Bower & Backer 1998). Superluminal motion of several jet components is detected with apparent velocities in the range of 10–40 c (Bower et al 1997; Jorstad et al 2001; Feng et al 2006; Hong et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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High-frequency very long baseline interferometry studies of NRAO 530

Lu¹,

Krichbaum²,

Zensus³

2011

Monthly Notices of the Royal Astronomical Society

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NRAO 530 is an optically violent variable source and has been studied with multi‐epoch multifrequency high‐resolution very long baseline interferometry (VLBI) observations. NRAO 530 was monitored with the Very Long Baseline Array (VLBA) at three frequencies (22, 43 and 86 GHz) on 10 consecutive days in 2007 May during observations of the Galactic Centre (Sgr A*). Furthermore, analysis of archival data of NRAO 530 at 15 GHz over the last 10 years allows us to study its detailed jet kinematics. We identified the compact component located at the southern‐end of the jet as the VLBI core, consistent with previous studies. The 10‐d monitoring data at the three high frequencies were shown to produce high‐quality and self‐consistent measurements of the component positions, from which we detected for the first time a two‐dimensional frequency‐dependent position shift. In addition, the repeated measurements also permit us to investigate the interday flux density and structure variability of NRAO 530. We find that it is more variable for the inner jet components than those further out. We obtained apparent velocities for eight jet components with βapp ranging from 2 to 26c. Accordingly, we estimated physical jet parameters with the minimum Lorentz factor of 14 and Doppler factors in the range of 14–28 (component f). The changes in the morphology of NRAO 530 were related to the motion of separate jet components with the most pronounced changes occurring in the regions close to the core. For NRAO 530, we estimated a position angle swing of 34 per year for the entire inner jet (components d and e). The non‐ballistic motion and change of jet orientation make this source another prominent example of a helical and possibly ‘swinging’ jet.

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Section: Resultssupporting

confidence: 92%

Section: Introductioncontrasting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

High-frequency very long baseline interferometry studies of NRAO 530

Lu¹,

Krichbaum²,

Zensus³

2011

Monthly Notices of the Royal Astronomical Society

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“…In addition, although the turnover is usually located in high frequencies (>43 GHz), this is not always the case (Rabaça & Zensus 1994;Fromm 2015) and is different for every blazar. The location of the turnover frequency has also been shown to change, moving either to higher or lower frequencies during outbursts (Feng et al 2006;Fromm 2015). Recent results from the F-GAMMA survey show that the turnover frequency can range from < 2.6 to > 86 GHz in a single source (Angelakis et al in prep., also Angelakis et al 2012).…”

Section: Observed Versus Turnover Radio Frequencymentioning

confidence: 99%

Reconciling inverse-Compton Doppler factors with variability Doppler factors in blazar jets

Liodakis

Zezas

Angelakis

et al. 2017

A&A

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Context. Blazar population models have shown that the inverse-Compton and variability Doppler factor estimates yield consistent results at the population level for flat spectrum radio quasars (FSRQs). The two methods, however, are inconsistent when compared on a source-by-source basis. Aims. In this work, we attempt to understand the source of the discrepancy by tracing the potential sources of systematic and statistical error for the inverse-Compton Doppler factors. By eliminating these sources of error, we provide stronger constrains on the value of the Doppler factor in blazar jets. Methods. We re-estimate the inverse-Compton Doppler factor for 11 sources that meet certain criteria for their synchrotron peak frequency and the availability of Doppler factor estimates in the literature. We compare these estimates with the average of two different estimates of the variability Doppler factor obtained using various datasets and methodologies to identify any discrepancies and, in each case, trace their sources in the methodology or assumptions adopted. Results. We identify three significant sources of error for the inverse-Compton Doppler factors: a) contamination of the X-ray flux by non-synchrotron self-Compton emission; b) radio observations at frequencies other than the synchrotron turnover frequency; c) non-simultaneity between radio and X-ray observations. We discuss key aspects in the correct application of the inverse-Compton method in light of these potential errors. We are able to constrain the Doppler factor of 3C273, 3C345, 3C454.3, PKS1510-089, and PKS1633+382 effectively, since all available estimates from both methods converge to the same values for these five sources.

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The parsec-scale jet of PKS 1749+096

Shen

Krichbaum

et al. 2012

A&A

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Context. PKS 1749+096 is a BL Lac object showing weak extended jet emission to the northeast of the compact VLBI core on parsec scales. Aims. We aim at better understanding the jet kinematics and variability of this source and finding clues that may applicable to other BL Lac objects. Methods. The jet was studied with multi-epoch multi-frequency high-resolution VLBI observations. Results. The jet is characterized by a one-sided curved morphology at all epochs and all frequencies. The VLBI core, located at the southern end of the jet, was identified based on its spectral properties. The equipartition magnetic field of the core was investigated, through which we derived a Doppler factor of 5, largely consistent with that derived from kinematics (component C5). The study of the detailed jet kinematics at 22 and 15 GHz, spanning a period of more than 10 years, indicates the possible existence of a bimodal distribution of the jet apparent speed. Ballistic and non-ballistic components are found to coexist in the jet. Superluminal motions in the range of 5-21 c were measured in 11 distinct components. We estimated the physical jet parameters with the minimum Lorentz factor of 10.2 and Doppler factors in the range of 10.2-20.4 (component C5). The coincidence in time of the component's ejection and flares supports the idea that, at least in PKS 1749+096, ejection of new jet components is connected with major outbursts in flux density. For the best-traced component (C5) we found that the flux density decays rapidly as it travels downstream the jet, accompanied by a steepening of its spectra, which argues in favor of a contribution of inverse Compton cooling. These properties make PKS 1749+096 a suitable target for an intensive monitoring to decipher the variability phenomenon of BL Lac objects.

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Multi-frequency VLBI observations of NRAO 530

Cited by 15 publications

References 23 publications

High-frequency very long baseline interferometry studies of NRAO 530

High-frequency very long baseline interferometry studies of NRAO 530

Reconciling inverse-Compton Doppler factors with variability Doppler factors in blazar jets

The parsec-scale jet of PKS 1749+096

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