VLBA Observations of Radio Reference Frame Sources. I.

Fey, A. L.; Clegg, Andrew W.; Fomalont, Edward B.

doi:10.1086/192315

Cited by 137 publications

(160 citation statements)

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“…Data reduction for these observations is essentially identical and is described in Fey, Clegg, & Fomalont (1996) and Fey & Charlot (1997). The RRFID data were collected with only 16 MHz total bandwidth, one-fourth of the bandwidth of the current observations.…”

Section: Observations and Data Analysismentioning

confidence: 99%

Anisotropic Interstellar Scattering toward the Cygnus Region

Desai¹,

Fey²

2001

ASTROPHYS J SUPPL S

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We were unable to reliably determine scattering disk parameters for 2021]317 at frequencies from 8.5 GHz down to 1.67 GHz because of its complex intrinsic source structure. The scattering disks are elliptical with axial ratios of about 0.75 : 1 with little measurable variation between these sources. We interpret our measurements as due to the e †ects of anisotropic interstellar turbulence. The anisotropy parameters, axial ratio and position angle, for those sources for which we have data at multiple frequencies appear to be frequency-independent making refractive distortions of isotropic turbulence an unlikely explanation. Our estimates of b, the power-law index of the power spectrum of electron density Ñuctuations, based upon direct model Ðts to the data on a source-by-source and frequency-by-frequency basis, are consistent with b \ 4 for most of the data but are strongly a †ected by our estimate of the intrinsic structure of the sources. Two of these sources, 2005]403 and 2021]317, exhibit signiÐcant intrinsic source structure at frequencies as low as 1.67 GHz, while the other two, 2008]332 and 2048]312, lack discernible source structure at frequencies lower then 2.3 GHz. The frequency scalings of the scattered angular sizes are also consistent with b \ 4. We discuss the implications of our measurements for the inner and outer scales of the turbulence.

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Section: Observations and Data Analysismentioning

confidence: 99%

Anisotropic Interstellar Scattering toward the Cygnus Region

Desai¹,

Fey²

2001

ASTROPHYS J SUPPL S

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“…We have collected published VLBI data from the literature with observations dating back to the early 1980s (Roberts et al 1987, Gabuzda et al 1989, Gabuzda & Cawthorne 1996, Vicente et al 1996, Fey et al 1996, Tateyama et al 1996, 1999, Fey & Charlot 1997, Rantakyrö et al 1998, Gabuzda & Gomez 2001, Tateyama & Kingham 2004, Ojha et al 2004, Jorstad et al 2001, 2005, Piner et al 2007, D'Arcangelo et al 2009). In addition, we have analysed 79 epochs of 15 GHz VLBA observations from the MOJAVE database (Lister et al 2009a), resulting in altogether 196 epochs of VLBI observations.…”

Section: Vlbi Datamentioning

confidence: 99%

Jet-disk connection in OJ287

Valtonen¹,

Savolainen²,

Wiik³

2010

Proc. IAU

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Abstract.A 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.

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“…It has been observed and studied with different VLBI arrays at a range of different frequencies (e.g., Eckart et al 1986Eckart et al , 1987Witzel et al 1988;Charlot 1990;Strom & Biermann 1991;Fey et al 1996;Gabuzda 1999;Gabuzda & Cawthorne 2000;Gabuzda & Chernetskii 2003;Ros et al 2000Ros et al , 2001Britzen et al 2005aBritzen et al ,b, 2008). …”

Section: Application To 1803+784mentioning

confidence: 99%

The origin of intrinsic variability of intraday variable sources

Roland

Britzen

Witzel

et al. 2009

A&A

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Intraday variability (IDV) describes flux-density variations in the radio regime on timescales of a day and less. The origin of such variations has been attributed to both source intrinsic and extrinsic mechanisms. While there is growing evidence that faster fluxdensity variations (on the order of hours to minutes) are caused by refractive interstellar scattering, extrinsic mechanisms alone still fail to explain all the observations. In particular, in the blazar S5 0716+714, correlated variations at frequencies in the radio and the optical regimes indicate an intrinsic component to the variability. Using the characteristics of the relativistic ejection found for the blazar S5 1803+784, we find that the formation and the rotation of a warp in the inner part of the accretion disk produce a small perturbation of the relativistic beam and consequently a variation in the viewing angle and in the beamed synchrotron emission. We find that the relative flux variations become chaotic if the amplitude of the perturbation exceeds a critical value. We investigate the properties of the chaotic behavior of the solution to explain the observed properties of IDV sources, such as the flux variations, the polarized flux variations, and the observable frequency dependence. As a warp can form naturally in the inner part of the accretion disk, we conclude that both intrinsic and extrinsic mechanisms produce IDV sources.

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VLBA Observations of Radio Reference Frame Sources. I.

Cited by 137 publications

References 0 publications

Anisotropic Interstellar Scattering toward the Cygnus Region

Anisotropic Interstellar Scattering toward the Cygnus Region

Jet-disk connection in OJ287

The origin of intrinsic variability of intraday variable sources

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