VLBI using a telescope in Earth orbit. II - Brightness temperatures exceeding the inverse Compton limit

Linfield, R. P.; Levy, G. S.; Ulvestad, J. S.; Edwards, C. D.; Dinardo, S. J.; Stavert, L. R.; Ottenhoff, C. H.; Whitney, A. R.; Cappallo, R. J.; Rogers, A. E. E.; Hirabayashi, H.; Morimoto, Manabu; Inoue, Makoto; Jauncey, D. L.; Nishimura, Tetsuro

doi:10.1086/167081

Cited by 86 publications

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“…This procedure is described in Section 2.4. (Linfield et al 1989), used for gain calibration. Unfortunately, due to hardware issues, we were only able to process right-hand circular polarization.…”

Section: Discussionmentioning

confidence: 99%

A Multiwavelength Study of the High Surface Brightness Hot Spot in PKS 1421–490

Godfrey

Bicknell

Lovell

et al. 2009

ApJ

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Long Baseline Array imaging of the z = 0.663 broadline radio galaxy PKS 1421−490 reveals a 400 pc diameter high surface brightness hot spot at a projected distance of ∼40 kpc from the active galactic nucleus. The isotropic X-ray luminosity of the hot spot, L 2-10 keV = 3 × 10 44 ergs s −1 , is comparable to the isotropic X-ray luminosity of the entire X-ray jet of PKS 0637−752, and the peak radio surface brightness is hundreds of times greater than that of the brightest hot spot in Cygnus A. We model the radio to X-ray spectral energy distribution using a one-zone synchrotron self-Compton model with a near equipartition magnetic field strength of 3 mG. There is a strong brightness asymmetry between the approaching and receding hotspots and the hot spot spectrum remains flat (α ≈ 0.5) well beyond the predicted cooling break for a 3 mG magnetic field, indicating that the hotspot emission may be Doppler beamed. A high plasma velocity beyond the terminal jet shock could be the result of a dynamically important magnetic field in the jet. There is a change in the slope of the hotspot radio spectrum at GHz frequencies, which we model by incorporating a cutoff in the electron energy distribution at γ min ≈ 650, with higher values implied if the hotspot emission is Doppler beamed. We show that a sharp decrease in the electron number density below a Lorentz factor of 650 would arise from the dissipation of bulk kinetic energy in an electron/proton jet with a Lorentz factor Γ jet 5.

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Section: Discussionmentioning

confidence: 99%

A Multiwavelength Study of the High Surface Brightness Hot Spot in PKS 1421–490

Godfrey

Bicknell

Lovell

et al. 2009

ApJ

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“…The brightness temperatures of the strongest compact sources determined at gigahertz frequencies with the finest resolution obtainable from ground-based interferometry are, coincidentally, ϳ10 12 K, which is similar to the inverse Compton limit. A number of sources (15,32) were found to have source frame brightness temperatures Ͼ10 12 K. These brightness temperatures were interpreted as being due to bulk relativistic motion close to the line of sight, with the inferred Doppler factors being consistent with those determined from superluminal motion studies (32). Measurements of brightness temperatures on Earth-space baselines, a primary aim of the VSOP Survey Program, will be of great importance in determining whether the 10 12 K cutoff is approached in the cores of extragalactic radio sources or whether, as has been suggested, some mechanism prevents radical departures from minimum energy and equipartition in these objects (33).…”

Section: Discussionmentioning

confidence: 99%

Overview and Initial Results of the Very Long Baseline Interferometry Space Observatory Programme

Hirabayashi

Hirosawa

Kobayashi

et al. 1998

Science

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168

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High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli–arc-second–scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here, VSOP images of the gamma-ray source 1156+295, the quasar 1548+056, the ultraluminous quasar 0014+813, and the superluminal quasar 0212+735 are presented and discussed.

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“…a 15th magnitude BL Lac object of unknown redshift (White et al 1988). It is amongst the most compact, submilliarcsecond, radio sources known based on space VLBI observations at 2.3 GHz (Linfield et al 1989) and 5 GHz (Hirabayashi et al 2000). The overall spectrum from 0.4 to 22 GHz as determined from measurements at the RATAN 600 over several epochs (Kovalev et al 1999) is given in Figure 2.…”

Section: Figurementioning

confidence: 99%

Variability in GPS Sources

Jauncey

King

Bignall

et al. 2003

Publ. – Astron. Soc. Aust

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Flux density monitoring data at 2.3 and 8.4 GHz is presented for a sample of 33 southern hemisphere GPS sources, drawn from the 2.7 GHz Parkes survey. This monitoring data, together with VLBI monitoring data, shows that a small fraction of these sources, ∼10%, vary. Their variability falls into several categories: sources whose spectral classification is, at best, ephemeral on a timescale of years; sources with a stable GPS classification that vary, but retain their classification; and a small number of sources that exhibit interstellar scintillation, but that maintain a mean GPS spectrum. Existing data on GPS sources with higher frequency peaks, ≥3 GHz, reveals that many such sources vary. However, the majority of these sources possess a GPS spectrum only during outbursts, and hence should perhaps be classified as ephemeral GPS sources. In addition, significant levels of circular polarisation have been found in a number of GPS sources, both amongst the variables and non-variables. Remarkable amongst these is PKS 1519−273, which possesses strong and variable circular polarisation, and which exhibits IDV in all Stokes parameters.

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VLBI using a telescope in Earth orbit. II - Brightness temperatures exceeding the inverse Compton limit

Cited by 86 publications

References 0 publications

A Multiwavelength Study of the High Surface Brightness Hot Spot in PKS 1421–490

A Multiwavelength Study of the High Surface Brightness Hot Spot in PKS 1421–490

Overview and Initial Results of the Very Long Baseline Interferometry Space Observatory Programme

Variability in GPS Sources

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