Long-term variability of a complete sample of flat-spectrum radio sources at declinations of 4°–6° (B1950)

Gorshkov, A. G.; Konnikova, V. K.; Мингалиев, М. Г.

doi:10.1134/s1063772908040033

Cited by 12 publications

(14 citation statements)

References 17 publications

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“…Within the uncertainties, the spectral indices in the optically thick range do not depend on the source type, and are close to the values obtained in [7]. Only six objects (two objects of each type) have ν max < 21.7 GHz, which determine the spectral index in the optically thin range.…”

Section: Comments On Long-term Variability and Spectrasupporting

confidence: 69%

“…For BL Lac objects, ν max = 2.3 and 4.8 GHz, and for one galaxy ν max = 7.7 GHz. Thus, α is basically determined by BL Lac objects and galaxies, and coincides within the errors with the similar estimate obtained in [7]. The nearly complete absence of quasars in the optically thin range, together with the fact that their mean angular sizes are the same as those for the other types of sources, could indicate either a different degree of inhomogeneity of their radiating regions or a much higher magnetic field intensity in quasars.…”

Section: Comments On Long-term Variability and Spectrasupporting

confidence: 65%

“…We calculated the flare time scales τ var for sources with detected flares. This time scale was defined as in the paper [7], which considered long-term variability of sources at declinations 4 • −6 • : τ var = dt/d ln S. The technique used to determine τ var was proposed in [23]. This quantity remains constant if the fluxdensity variations during the flare have an exponential character.…”

Section: Sources With Detected Flaresmentioning

confidence: 99%

“…In [7], we reported the results of 20-year RATAN-600 studies of the long-term variability of a complete sample of flat-spectrum radio sources with α 3.9−7.7 GHz > −0.5 (S ∝ ν α ). This sample includes 68 sources with flux densities S > 200 mJy from the Zelenchuk Survey at 3.9 GHz, at declinations 4 • −6 • (B1950), at all right ascensions, and at Galactic latitudes |b| > 15 • [8].…”

Section: Introductionmentioning

confidence: 98%

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Long-term variability of a complete sample of flat-spectrum radio sources at declinations 10°–12°30′ (J2000)

2012

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The paper reports the results of ten-year centimeter-wavelength observations with the RATAN-600 radio telescope of a complete sample of 83 flat-spectrum sources from the GB6 catalog of the MGB Survey, with S 4.85 > 200 mJy at declinations 10 • −12 • 30 . Starting in 2000, the observations were conducted simultaneously at six frequencies in the range 0.97-21.7 GHz. Seventy-six sources (including 54 quasars) have been identified with optical objects, which have redshifts in the range z = 0.331−3.601. Analysis of light curves and spectra at different activity phases has shown that, in most cases, the dynamics of the development of flares is consistent with a model in which the variability results from the evolution of a shock in a radio jet. A relationship between the time scales for the rise and fall of the flares has been found. There is no redshift dependence of the true linear dimensions of the radiating regions and the variability indices obtained over ten years. These facts can be interpreted as an absence of cosmological evolution of quasars at least up to z ≈ 3.

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Section: Comments On Long-term Variability and Spectrasupporting

confidence: 69%

Section: Comments On Long-term Variability and Spectrasupporting

confidence: 65%

Section: Sources With Detected Flaresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

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Long-term variability of a complete sample of flat-spectrum radio sources at declinations 10°–12°30′ (J2000)

2012

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“…The results of these long-term studies were reported in many publications by the researchers from the Sternberg Astronomical Institute, the Special Astrophysical Observatory of the Russian Academy of Sciences, and the Astro Space Center of the Lebedev Physical Institute of the Russian Academy of Sciences, e.g. [7][8][9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

On possibility of detection of variable sources using the data of “Cold” surveys carried out on RATAN-600

Majorova

Желенкова

2012

Astrophys. Bull.

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In this study we attempt to assess the possibility of detection of variable sources using the data of the 7.6-cm wavelength surveys carried out on the RATAN-600 radio telescope in the period from 1980 through 1994. Objects selected according to certain criteria from the RCR catalog are used to construct the calibration curves and to estimate the accuracy of the resulting calibration curves and determine the r.m.s. errors for the measured source flux densities. To check the calibration sources for the presence of variable objects, quantitative estimates are performed for a number of parameters that characterize variability, in particular, for the long-term variability index V and the χ 2 (chi-square) probability p. The long-term variability index was found to be positive for 14 out of approximately 80 calibration sources, possibly indicating that these sources are variable. The most likely candidate variables are the three sources with the χ 2 probability p > 0.95. Five sources have χ 2 probabilities in the 0.85 < p < 0.95 interval, and the remaining six in the 0.6 < p < 0.8 interval.Nine out of 14 objects are possibly variable in the optical range. The light curves and spectra are determined for possible variable sources and a number of "non-variable" objects. We plan to use the results of this study in our future searches for variable radio sources using the data of the "Cold" surveys.

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Two active states of the narrow-line gamma-ray-loud AGN GB 1310+487

Sokolovsky¹,

Schinzel²,

Tanaka³

et al. 2014

A&A

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Context. Previously unremarkable, the extragalactic radio source GB 1310+487 showed a γ-ray flare on 2009 November 18, reaching a daily flux of ∼10 −6 photons cm −2 s −1 at energies E > 100 MeV and became one of the brightest GeV sources for about two weeks. Its optical spectrum shows strong forbidden-line emission while lacking broad permitted lines, which is not typical for a blazar. Instead, the spectrum resembles those of narrow emission-line galaxies. Aims. We investigate changes in the object's radio-to-GeV spectral energy distribution (SED) during and after the prominent γ-ray flare with the aim of determining the nature of the object and of constraining the origin of the variable high-energy emission. Methods. The data collected by the Fermi and AGILE satellites at γ-ray energies; Swift at X-ray and ultraviolet (UV); the Kanata, NOT, and Keck telescopes at optical; OAGH and WISE at infrared (IR); and IRAM 30 m, OVRO 40 m, Effelsberg 100 m, RATAN-600, and VLBA at radio are analyzed together to trace the SED evolution on timescales of months. Results. The γ-ray/radio-loud narrow-line active galactic nucleus (AGN) is located at redshift z = 0.638. It shines through an unrelated foreground galaxy at z = 0.500. The AGN light is probably amplified by gravitational lensing. The AGN SED shows a two-humped structure typical of blazars and γ-ray-loud narrow-line Seyfert 1 galaxies, with the high-energy (inverse-Compton) emission dominating by more than an order of magnitude over the low-energy (synchrotron) emission during γ-ray flares. The difference between the two SED humps is smaller during the low-activity state. Fermi observations reveal a strong correlation between the γ-ray flux and spectral index, with the hardest spectrum observed during the brightest γ-ray state. The γ-ray flares occurred before and during a slow rising trend in the radio, but no direct association between γ-ray and radio flares could be established. Conclusions. If the γ-ray flux is a mixture of synchrotron self-Compton and external Compton emission, the observed GeV spectral variability may result from varying relative contributions of these two emission components. This explanation fits the observed changes in the overall IR to γ-ray SED.

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Long-term variability of a complete sample of flat-spectrum radio sources at declinations of 4°–6° (B1950)

Cited by 12 publications

References 17 publications

Long-term variability of a complete sample of flat-spectrum radio sources at declinations 10°–12°30′ (J2000)

Long-term variability of a complete sample of flat-spectrum radio sources at declinations 10°–12°30′ (J2000)

On possibility of detection of variable sources using the data of “Cold” surveys carried out on RATAN-600

Two active states of the narrow-line gamma-ray-loud AGN GB 1310+487

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