Intraday Variability and Microarcsecond Structure in Blazar Cores

Jauncey, D. L.; Kedziora-Chudczer, Lucyna; Lovell, J. E. J.; Macquart, Jean-Pierre; Nicolson, G. D.; Perley, R. A.; Reynolds, John E.; Tzioumis, Anastasios; Wieringa, M.; Bignall, Hayley

doi:10.1017/s0074180900220524

Cited by 3 publications

(1 citation statement)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Time-delay measurements of the variability pattern arrival time between two sites located at different places of the Earth were successfully performed in the case of PKS0405-385 [4], J1819+3845 [3] and PKS1257-326 [5]. These measurements however are only feasible in the case of IDV sources showing extremely rapid variations (also called intra-hour variable sources), when changes in the flux density can be detected (with high accuracy) within tens of seconds [6].…”

Section: Introductionmentioning

confidence: 99%

A Newly Discovered Highly Variable IDV Source

Gabányi¹,

Marchili²,

Krichbaum³

et al. 2008

Proceedings of Bursts, Pulses and Flickering: Wide-Field Monitoring of the Dynamic Radio Sky — PoS(Dynamic2007)

View full text Add to dashboard Cite

Short time scale radio variations of compact extragalactic radio quasars and blazars known as IntraDay Variability (IDV) can be explained in at least some sources as a propagation effect; the variations are interpreted as scintillation of radio waves in the turbulent interstellar medium of the Milky Way. One of the most convincing observational arguments in favour of a propagationinduced variability scenario is the observed annual modulation in the characteristic variability time scale due to the Earth's orbital motion. So far there are only two sources known with a well-constrained seasonal cycle. J1128+592 is a recently discovered, highly variable IDV source. Previous, densely time-sampled flux-density measurements with the Effelsberg 100-m radio telescope (Germany) and the Urumqi 25-m radio telescope (China), strongly indicate an annual modulation of the time scale. Here, we summarise the annual modulation model derived using all the measurements, carried out in the last 2.5 years.

show abstract

Section: Introductionmentioning

confidence: 99%

A Newly Discovered Highly Variable IDV Source

Gabányi¹,

Marchili²,

Krichbaum³

et al. 2008

Proceedings of Bursts, Pulses and Flickering: Wide-Field Monitoring of the Dynamic Radio Sky — PoS(Dynamic2007)

View full text Add to dashboard Cite

show abstract

The Parkes quarter-Jansky flat-spectrum sample

Jackson

Wall

Shaver

et al. 2002

A&A

View full text Add to dashboard Cite

Abstract. We present a new sample of quarter-Jansky flat-spectrum radio sources selected to search for highredshift quasars and to study the evolution of the flat-spectrum quasar population. The sample comprises 878 radio sources selected from the Parkes catalogues with spectral indices α 5 GHz 2.7 GHz ≥ −0.4 where Sν ∝ ν α . The sample covers all right ascensions and the declination range from −80.• 0 to +2.• 5, excluding low galactic latitudes (| b |< 10• ) and the Magellanic Cloud regions. We have obtained improved radio source positions, firstly to reconfirm the majority of the existing identifications, and secondly, using digitized sky-survey data and deep B, Gunn-i and Gunn-z CCD-imaging, to find optical identifications for 223 previously-unidentified sources. We present the final catalogue of 878 flat-spectrum sources: 827 are compact radio sources identified with galaxies, quasars and BL Lac objects, 38 have either extended radio structure or are identified with Galactic objects (PN, HII or non-compact radio source), 4 are obscured by Galactic stars, and 9 (1 per cent of the total sample) remain unidentified.

show abstract

The IDV source J 1128+5925, a new candidate for annual modulation?

Gabányi

Marchili²,

Krichbaum³

et al. 2007

A&A

View full text Add to dashboard Cite

Context. Short time-scale radio variations of compact extragalactic radio sources, known as IntraDay Variability (IDV), can be explained in at least some sources by a source-extrinsic effect, in which the variations are interpreted as scintillation of radio waves caused by the turbulent interstellar medium of the Milky Way. One of the most convincing observational arguments in favour of propagation-induced variability is the so-called "annual modulation" of the characteristic variability time-scale, which is due to the orbital motion of the Earth. So far there are only two sources known which show such a well-defined seasonal cycle, a few more sources with fewer data can be regarded as possible candidates for this effect. However, source-intrinsic effects, such as structural variations, can also cause the observed changes of the variability time-scale. Data for the new, recently discovered, and highly variable IDV source J 1128+5925 are presented. Aims. We study the frequency and time dependence of the IDV in this compact quasar. We measure the characteristic variability time-scale of the IDV throughout the year, and analyze whether the observed changes in the variability time-scale are consistent with annual modulation. Assuming a radio wave propagation effect as origin, we are able to constrain some physical properties (such as distance, scattering-strength, and possible anisotropy) of the "plasma" screen, which may cause the scintillation. Methods. We monitored the flux density variability of J 1128+5925 with dense time sampling between 2.7 and 10.45 GHz. We observed with the 100 m Effelsberg radio telescope of the Max-Planck-Institut für Radioastronomie (MPIfR) at 2.70 GHz, 4.85 GHz, and 10.45 GHz, as well as with the 25 m Urumqi radio telescope (China) at 4.85 GHz. From ten observing sessions, each of which lasted several days during the period between 2004-2006, we determine the variability characteristics and time-scales which we investigate in view of possible scintillation and annual modulation. Results. The observed pronounced changes of the variability time-scale of J 1128+5925 are modelled with an anisotropic annual modulation model. The observed frequency dependence of the variation is in good agreement with the prediction from interstellar scintillation. Adopting a simple model for the annual modulation model and also using the frequency dependence of the IDV, we derive a lower limit to the distance the scattering screen and an upper limit for the scintillating source size. The latter is found to be consistent with the measured core size from Very Long Baseline Interferometry (VLBI).

show abstract

Intraday Variability and Microarcsecond Structure in Blazar Cores

Cited by 3 publications

References 13 publications

A Newly Discovered Highly Variable IDV Source

A Newly Discovered Highly Variable IDV Source

The Parkes quarter-Jansky flat-spectrum sample

The IDV source J 1128+5925, a new candidate for annual modulation?

Contact Info

Product

Resources

About