Quasi-simultaneous five-frequency VLBA observations of PKS 0528+134

Cai, H.-B.; Shen, Zhi-Qiang; Chen, X.; Shang, L.-L.

doi:10.1051/0004-6361:20065094

Cited by 3 publications

(2 citation statements)

References 29 publications

(38 reference statements)

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“…Rotating jet patterns have been discussed in the literature in connection with VLBI observations of morphologically "curved" or "bent" jets, and of apparent helical motion of parsec-scale jet components (Zensus 1997;Kellermann et al 2004). Among the sources for which we find a variability pattern matched with the rotating jet model, curved and potentially helical VLBI jets have been observed in J0423−0120 (Wagner et al 1995;Britzen et al 2001), J0530+1332 (Pohl et al 1996;Cai et al 2006), J0721+7120 (Bach et al 2005), J1159+2914 (Hong et al 2004;Zhao et al 2011), J1337−1257 (Lister et al 2009), J1613+3412 (Piner & Kingham 1997), and J1924−2914(Shen et al 1999Lister et al 2009). Helical structures have also been found in the VLBI jet of FSRQ J1310+3220 (Cassaro et al 2002), for which a rotating pattern with essentially constant period is largely consistent with the flux variation pattern shown in the Metsähovi 37 GHz data (Sect.…”

Section: Geometric Variability and Helical Jetssupporting

confidence: 67%

Long-term variability of extragalactic radio sources in thePlanckEarly Release Compact Source Catalogue

Chen

Rachen

López‐Caniego

et al. 2013

A&A

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Combining measurements taken using the Wilkinson Microwave Anisotropy Probe (WMAP) from 2001 to 2008 with measurements taken using Planck from 2009 to 2010, we investigate the long-term flux density variability of extragalactic radio sources selected from the Planck Early Release Compact Source Catalogue. The single-year, single-frequency WMAP maps are used to estimate yearly-averaged flux densities of the sources in the four WMAP bands: Ka (33 GHz), Q (41 GHz), V (61 GHz), and W (94 GHz). We identify 82, 67, 32, and 15 sources respectively as variable at greater than 99% confidence level in these four bands. The amplitudes of variation are comparable between bands, and are not correlated with either the flux densities or the spectral indices of the sources. The number counts of WMAP Ka-band sources are stable from year to year despite the fluctuation caused by individual source variability. Most of our sources show strong correlation in variability between bands. Almost all the sources that show variability are blazars. We have attempted to fit two simple, four-parameter models to the time-series of 32 sources showing correlated variability at multiple frequencies -a long-term flaring model and a rotating-jet model. We find that 19 sources (60%) can be fit with the simple rotating-jet model, and ten of these also fit the simple long-term flaring model. The remaining 13 sources (40%) show more complex variability behaviour that is not consistent with either model. Extended radio galaxies in our sample show no sign of variability, as expected, with the exception of Pictor A for which we report evidence for a millimetre flare lasting between 2002 and 2010.

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Section: Geometric Variability and Helical Jetssupporting

confidence: 67%

Long-term variability of extragalactic radio sources in thePlanckEarly Release Compact Source Catalogue

Chen

Rachen

López‐Caniego

et al. 2013

A&A

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“…Unfortunately due to the lack of the corresponding VLBA observations for other compact amplitude calibrators, we could not perform any absolute amplitude calibration. Based on our experience of the study on PKS 0528+134 and 3C 138 by the multi-frequency VLBA observations (Cai et al 2006;Shen et al 2005), the errors in the absolute flux-density calibration are about 10% at 2.3 and 8.4 GHz, and about 20% at 22.2 GHz. We also used the Difwrap program (Lovell 2000) to estimate the errors of the Gaussian model-fitting parameters.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Multi-epoch VLBA observations of 3C 66A

Cai

Shen

Sudou

et al. 2007

A&A

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We present the results of six-epoch Very Long Baseline Array (VLBA) observations of 3C 66A. The high-resolution Very Long Baseline Interferometer (VLBI) maps obtained at multi-frequency (2.3, 8.4, and 22.2 GHz) simultaneously enabled us to identify the brightest compact component with the core. We find that the spectrum of the core can be reasonably fitted by the synchrotron self-absorption model. Our VLBA maps show that the jet of 3C 66A has two bendings at about 1.2 and 4 mas from the core. We also give possible identifications of our jet components with the components in previous VLBA observations by analysing their proper motions. We find consistent differences of the position from the core in one component between different frequencies at six epochs.

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Phase-Reference VLBI Observations of the Compact Steep-Spectrum Source 3C 138

Shen

Shang

Jiang

et al. 2006

Publications of the Astronomical Society of Japan

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We investigate a phase-reference VLBI observation that was conducted at 15.4 GHz by fast switching VLBA antennas between the compact steep-spectrum radio source 3C 138 and the quasar PKS 0528+134 which are about 4 • away on the sky. By comparing the phase-reference mapping with the conventional hybrid mapping, we demonstrate the feasibility of high precision astrometric measurements for sources separated by 4 • . VLBI phase-reference mapping preserves the relative phase information, and thus provides an accurate relative position between 3C 138 and PKS 0528+134 of ∆α = −9 m 46 s .531000 ± 0 s .000003 and ∆δ = 3 • 6 ′ 26 ′′ .90311 ± 0 ′′ .00007 (J2000.0) in right ascension and declination, respectively. This gives an improved position of the nucleus (component A) of 3C 138 in J2000.0 to be RA=05 h 21 m 9 s .885748 and Dec=16 • 38 ′ 22 ′′ .05261 under the assumption that the position of calibrator PKS 0528+134 is correct. We further made a hybrid map by performing several iterations of CLEAN and self-calibration on the phase-referenced data with the phase-reference map as an input model for the first phase self-calibration. Compared with the hybrid map from the limited visibility data directly obtained from fringe fitting 3C 138 data, this map has a similar dynamic range, but a higher angular resolution. Therefore, phase-reference technique is not only a means of phase connection, but also a means of increasing phase coherence time allowing self-calibration technique to be applied to much weaker sources.

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Quasi-simultaneous five-frequency VLBA observations of PKS 0528+134

Cited by 3 publications

References 29 publications

Long-term variability of extragalactic radio sources in thePlanckEarly Release Compact Source Catalogue

Long-term variability of extragalactic radio sources in thePlanckEarly Release Compact Source Catalogue

Multi-epoch VLBA observations of 3C 66A

Phase-Reference VLBI Observations of the Compact Steep-Spectrum Source 3C 138

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