Daily observations of compact radio sources at 2.7 and 8.1 GHz - 1979-1987

Waltman, E. B.; Fiedler, Russell; Johnston, K. J.; Spencer, J. H.; Florkowski, D. R.; Josties, F. J.; McCarthy, Dennis D.; Matsakis, Demetrios

doi:10.1086/191609

Cited by 32 publications

(25 citation statements)

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“…Var ∆S (8 GHz) = 7.33). Well below the peak the variability is less pronounced and at a time scale of five years during 1983-1988 the source was steady (S 2.7 GHz ≈ 5 Jy and S 8.2 GHz ≈ 5 Jy-7 Jy, Waltman et al 1991).…”

Section: B0743−006: Is a Gps Quasar Identified Bymentioning

confidence: 97%

Long term variability of gigahertz-peaked spectrum sources and candidates

Torniainen¹,

Tornikoski²,

Teräsranta³

et al. 2005

A&A

102

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Abstract.We have combined new data from our observing campaigns and data from the literature to construct the radio continuum spectra for a sample of mostly quasar-type high peaking gigahertz-peaked spectrum (GPS) source candidates. We have also studied the spectra and variability of so called "bona fide" GPS sources and other inverted-spectrum sources from the literature. For many of our sample sources we now have data spanning over two decades, enabling us to study their long term behaviour. Based on our earlier results we expected to find several new high peaking GPS sources. Instead we found out that even most of the "bona fide" GPS sources cease to adhere to the generic GPS source properties when using these well-sampled long term data sets. In our sample of 35 inverted-spectrum sources from the literature only five seem to be consistent with the GPS properties, and even out of these sources two are too sparsely sampled to firmly make conclusions about their variability. Thirteen of the "bona fide" GPS sources exhibit pronounced activity, which diverges from the low variability expected from these sources. None of our new candidates turned out to have both a convex spectrum and little to no variability, but there is one variable source with a consistently convex spectrum. All the rest have flat spectra, but the upper envelope of the spectrum is clearly convex for four extremely variable sources. Similar continuum spectra with a flat lower envelope and a convex upper envelope are observed for eight previously identified inverted-spectrum sources. According to this study the genuine quasar-type GPS sources are rare but there is a large number of highly variable sources that can have a convex spectrum peaking at high radio frequencies (up to ca. 100 GHz) during flares. Many of the GPS sources from the literature have too easily been classified as GPS sources based on too sparse data, and studying the long term variability is essential for identifying the sources with consistently convex continuum spectra.

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Section: B0743−006: Is a Gps Quasar Identified Bymentioning

confidence: 97%

Long term variability of gigahertz-peaked spectrum sources and candidates

Torniainen¹,

Tornikoski²,

Teräsranta³

et al. 2005

A&A

102

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“…The total radio flux density of 3C 345 has been monitored at 5, 8, and 15 GHz (Aller et al 2003), and at 22 and 37 GHz (Teräsranta et al 1998). The source has also been monitored with the Green Bank Interferometer at 2.7 and 8.1 GHz (Waltman et al 1991). The observed variability of the optical emission is possibly quasi-periodic with a period of ≈1560 days (Babadzhanyants & Belokon' 1984;Kidger 1989), although it has been suggested that the light curve may originate from a non-linear and non-stationary stochastic process (Vio et al 1991).…”

Section: The Quasar 3c 345mentioning

confidence: 99%

A supermassive binary black hole in the quasar 3C 345

Lobanov

Roland

2005

A&A

118

162

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Abstract. Radio loud active galactic nuclei present a remarkable variety of signs indicating the presence of periodical processes possibly originating in binary systems of supermassive black holes, in which orbital motion and precession are ultimately responsible for the observed broad-band emission variations, as well as for the morphological and kinematic properties of the radio emission on parsec scales. This scenario, applied to the quasar 3C 345, explains the observed variations of radio and optical emission from the quasar, and reproduces the structural variations observed in the parsec-scale jet of this object. The binary system in 3C 345 is described by two equal-mass black holes with masses of ≈7.1 × 10 8 M separated by ≈0.33 pc and orbiting with a period ∼480 yr. The orbital motion induces a precession of the accretion disk around the primary black hole, with a period of ≈2570 yr. The jet plasma is described by a magnetized, relativistic electron-positron beam propagating inside a wider and slower electron-proton jet. The combination of Alfvén wave perturbations of the beam, the orbital motion of the binary system and the precession of the accretion disk reproduces the variability of the optical flux and evolution of the radio structure in 3C 345. The timescale of quasi-periodic flaring activity in 3C 345 is consistent with typical disk instability timescales. The present model cannot rule out a small-mass orbiter crossing the accretion disk and causing quasi-periodic flares.

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“…This huge data set was published by Waltman et al (1991). Additional observations carried out with new receivers at 2.25 GHz and at 8.3 GHz from 1989 to 1994 are also included in the database.…”

Section: Radio Observationsmentioning

confidence: 99%

30 years of multi-wavelength observations of 3C 273

Türler¹,

Paltani²,

Courvoisier³

et al. 1999

Astron. Astrophys. Suppl. Ser.

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Abstract. We present a wide multi-wavelength database of most observations of the quasar 3C 273 obtained during the last 30 years. This database is the most complete set of observations available for an active galactic nucleus (AGN). It contains nearly 20 000 observations grouped together into 70 light curves covering 16 orders of magnitude in frequency from the radio to the γ-ray domain.The database is constituted of many previously unpublished observations and of most publicly available data gathered in the literature and on the World Wide Web (WWW). It is complete to the best of our knowledge, except in the optical (UBV ) domain where we chose not to add all observations from the literature. In addition to the photometric data, we present the spectra of 3C 273 obtained by the International Ultraviolet Explorer (IUE) satellite. In the X-ray domain, we used the spectral fit parameters from the literature to construct the light curves.Apart from describing the data, we show the most representative light curves and the average spectrum of 3C 273. The database is available on the WWW in a homogeneous and clear form and we wish to update it regularly by adding new observations.Send offprint requests to: M. Türler (ISDC)

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Daily observations of compact radio sources at 2.7 and 8.1 GHz - 1979-1987

Cited by 32 publications

References 0 publications

Long term variability of gigahertz-peaked spectrum sources and candidates

Long term variability of gigahertz-peaked spectrum sources and candidates

A supermassive binary black hole in the quasar 3C 345

30 years of multi-wavelength observations of 3C 273

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