Quasi-Stellar Sources: Variation in the Radio Emission of 3C 273

Dent, W. A.

doi:10.1126/science.148.3676.1458

Cited by 106 publications

(40 citation statements)

References 10 publications

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“…The radio intensity variability of active galactic nuclei (AGNs) has been the subject of extensive study since its discovery by Dent (1965) and Sholomitskii (1965). The short timescales of variability of a few months at centimetric wavelengths implied such high brightness temperatures in these compact sources that bulk relativistic motions of the synchrotron-emitting plasma at angles close to the line of sight had to be invoked (for a review see Altschuler 1989).…”

Section: Introductionmentioning

confidence: 99%

14‐year Program Monitoring the Flux Densities of 33 Radio Sources at Low Frequencies

Salgado¹,

Altschuler²,

Ghosh³

et al. 1999

ASTROPHYS J SUPPL S

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We present the results of a low-frequency Ñux density monitoring program of 33 extragalactic radio sources. The light curves at 318 and 430 MHz over a 14 yr period are presented. The measurements were made with the NAIC Arecibo 305 m radio telescope at approximately bimonthly intervals between 1980 January and 1989 February and at less regular intervals between 1989 October and 1993 October, for a total of 64 observing sessions. In addition, we provide a Ðrst discussion of the results, pointing out several source properties and interesting objects.

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Section: Introductionmentioning

confidence: 99%

14‐year Program Monitoring the Flux Densities of 33 Radio Sources at Low Frequencies

Salgado¹,

Altschuler²,

Ghosh³

et al. 1999

ASTROPHYS J SUPPL S

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“…Following the identification of the first quasar 3C 273 [1,2], quasar variability was observed at optical wavelengths [3], and then at the radio wavelengths of 3.75 cm [4] and 32.5 cm [5]. At 3.75 cm, the variability was interpreted as intrinsic to the sources, as the observations displayed a timescale of a year or more.…”

Section: -1980s: Low Frequency Variabilitymentioning

confidence: 99%

Interstellar Scintillation and Scattering of Micro-arc-second AGN

et al. 2016

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Abstract:The discovery of the first quasar 3C 273 led directly to the discovery of their variability at optical and radio wavelengths. We review the radio variability observations, in particular the variability found at frequencies below 1 GHz, as well as those exhibiting intra-day variability (IDV) at cm wavelengths. Observations have shown that IDV arises principally from scintillation caused by scattering in the ionized interstellar medium of our Galaxy. The sensitivity of interstellar scintillation towards source angular sizes has provided a powerful tool for studying the most compact components of radio-loud AGN at microarcsecond and milliarcsecond scale resolution.Keywords: quasars; variability; interstellar scattering 1965-1980s: Low Frequency VariabilityFollowing the identification of the first quasar 3C 273 [1,2], quasar variability was observed at optical wavelengths [3], and then at the radio wavelengths of 3.75 cm [4] and 32.5 cm [5]. At 3.75 cm, the variability was interpreted as intrinsic to the sources, as the observations displayed a timescale of a year or more. However, at lower frequencies the observed variability of CTA102 did not fit this pattern. Sholomitskii's published 1964-65 Soviet telescope data is shown in Figure 1, for which he claimed detection of variability at 32.5 cm wavelength on a time-scale of months or less.

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“…85 a time-scale of years discovered in the first quasar, 3C273, at em wavelengths (Dent 1965) was seen to be intrinsic to the source. Several decades of milliarcsecond resolution VLBI observations have confirmed the intrinsic nature of such variations and revealed a close relationship between structural changes on parsec-scales and flux density variations.…”

Section: Idv and Microarcsecond Structure In Blazar Coresmentioning

confidence: 99%

Intraday Variability and Microarcsecond Structure in Blazar Cores

Jauncey

Kedziora-Chudczer

Lovell

et al. 2001

Symp. - Int. Astron. Union

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Abstract. The accumulation of evidence now strongly favours interstellar scintillation (ISS) as the principal mechanism causing intra-day variability (IDV) at em wavelengths. While ISS reduces the implied brightness temperatures, they remain uncomfortably high. The distance to the scattering screen is an important parameter in determining the actual brightness temperature encountered. The high brightness temperatures, the presence of strong and variable circular polarization and the observed lifetimes of a decade or more for several IDV sources, pose significant problems for synchrotron theory."The fault, dear Brutus, is not in our stars, but in ourselves, that we are underlings."

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Quasi-Stellar Sources: Variation in the Radio Emission of 3C 273

Abstract: Evidence is presented for the first time for large fractional variations in the radio emission of the quasi-stellar sources 3C 273, 3C 279, and 3C 345, all of which have flat radio spectra at centimeter wavelengths.

Cited by 106 publications

References 10 publications

14‐year Program Monitoring the Flux Densities of 33 Radio Sources at Low Frequencies

14‐year Program Monitoring the Flux Densities of 33 Radio Sources at Low Frequencies

Interstellar Scintillation and Scattering of Micro-arc-second AGN

Intraday Variability and Microarcsecond Structure in Blazar Cores

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