Detection statistics of the RadioAstron AGN survey

Kovalev, Y. Y.; Kardashëv, N. S.; Sokolovsky, K. V.; Voitsik, P. A.; An, Tao; Anderson, J. M.; Andrianov, A. S.; Avdeev, V. Yu.; Bartel, N.; Bignall, H. E.; Burgin, M. S.; Edwards, P. G.; Ellingsen, S. P.; Frey, S.; Garcı́a-Miró, C.; Gawroński, M.; Ghigo, F. D.; Ghosh, T.; Giovannini, G.; Girin, I. A.; Giroletti, M.; Gurvits, L. I.; Jauncey, D. L.; Horiuchi, S.; Иванов, Д.; Kharinov, M. A.; Koay, Jun Yi; Костенко, В. И.; Kovalenko, A. V.; Kravchenko, Evgeniya V.; Kunert-Bajraszewska, M.; Kutkin, A. M.; Лихачев, С. Ф.; Lisakov, M. M.; Litovchenko, I. D.; McCallum, Jamie; Melis, A.; Melnikov, Alexey; Migoni, Carlo; Nair, Dhanya G.; Pashchenko, I. N.; Phillips, Chris; Polatidis, A. G.; Pushkarev, A. B.; Quick, J.; Rakhimov, I. A.; Reynolds, C.; Rizzo, J. R.; Rudnitskiy, A. G.; Savolainen, Tuomas; Шахворостова, Н. Н.; Shatskaya, M. V.; Shen, Zhi; Щуров, М. А.; Vermeulen, R. C.; Vicente, P. de; Wolak, P.; Zensus, J. A.; Zuga, V. A.

doi:10.1016/j.asr.2019.08.035

Cited by 28 publications

(19 citation statements)

References 37 publications

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“…This difference between the maximum brightness temperatures we observe for most sources and the typical flaring value found by Liodakis et al (2018) may simply be due to the fact that we are measuring the brightness temperature of the core region of the jet as a whole, and even during an outburst, the core region may not consist of just a single flaring component. Indeed this suggestion is supported by the RadioAstron space VLBI measurements which can detect smaller sub-components in the jet core (Kovalev et al 2020c). They indicate higher peak brightness temperatures at 22 GHz in at least two powerful AGN jets at similar epochs to those we observed from the VLBA alone at 15 GHz.…”

Section: Intrinsic T B and Energy Balance In Jet Coressupporting

confidence: 80%

MOJAVE XIX: Brightness Temperatures and Intrinsic Properties of Blazar Jets

Homan,

Cohen,

Hovatta

et al. 2021

Preprint

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We present multi-epoch, parsec-scale core brightness temperature observations of 447 AGN jets from the MOJAVE and 2cm Survey programs at 15 GHz from 1994 to 2019. The brightness temperature of each jet over time is characterized by its median value and variability. We find that the range of median brightness temperatures for AGN jets in our sample is much larger than the variations within individual jets, consistent with Doppler boosting being the primary difference between the brightness temperatures of jets in their median state. We combine the observed median brightness temperatures with apparent jet speed measurements to find the typical intrinsic Gaussian brightness temperature of 4.1(±0.6)×10 10 K, suggesting that jet cores are at or below equipartition between particle and magnetic field energy in their median state. We use this value to derive estimates for the Doppler factor for every source in our sample. For the 309 jets with both apparent speed and brightness temperature data, we estimate their Lorentz factors and viewing angles to the line of sight. Within the BL Lac optical class, we find that high-synchrotron-peaked (HSP) BL Lacs have smaller Doppler factors, lower Lorentz factors, and larger angles to the line of sight than intermediate and low-synchrotron-peaked (LSP) BL Lacs. We confirm that AGN jets with larger Doppler factors measured in their parsec-scale radio cores are more likely to be detected in γ rays, and we find a strong correlation between γ-ray luminosity and Doppler factor for the detected sources.

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Section: Intrinsic T B and Energy Balance In Jet Coressupporting

confidence: 80%

MOJAVE XIX: Brightness Temperatures and Intrinsic Properties of Blazar Jets

Homan,

Cohen,

Hovatta

et al. 2021

Preprint

Self Cite

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“…Launched in 2011, Spektr-R was located on a highly elliptic orbit, with perigee of 350,000 km and an orbital period of approximately 9 days. It successfully observed using receivers at four wavelengths, extending from 1.3 cm to 92 cm (e.g., Popov et al 2017;Kovalev et al 2020). Our observations of Sgr A * include projected baselines 4 times the Earth's diameter, providing the sharpest view of this source at centimeter wavelengths and the first using space-VLBI.…”

Section: Introductionmentioning

confidence: 80%

“…Using the VLBI software processing package PIMA , we performed baseline-based fringe fitting, which included determination of the phase acceleration term to statistically separate observations with significant interferometric signal and http://astrogeo.org/pima/ noise. To do this, we applied the approach described in Petrov et al (2011) and Kovalev et al (2020) to estimate the probability of false detection (PFD) for each interferometric fringe obtained. Fringes with PFD > 10 −4 were classified as non-detections; for each non-detection, we computed the associated visibility amplitude upper limit.…”

Section: Observations Correlation and Processingmentioning

confidence: 99%

First Space-VLBI Observations of Sagittarius A*

Johnson,

Kovalev,

Lisakov

et al. 2021

Preprint

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We report results from the first Earth-space VLBI observations of the Galactic Center supermassive black hole, Sgr A * . These observations used the space telescope Spektr-R of the RadioAstron project together with a global network of 20 ground telescopes, observing at a wavelength of 1.35 cm. Spektr-R provided baselines up to 3.9 times the diameter of the Earth, corresponding to an angular resolution of approximately 55 𝜇as and a spatial resolution of 5.5𝑅 Sch at the source, where 𝑅 Sch ≡ 2𝐺 𝑀/𝑐 2 is the Schwarzschild radius of Sgr A * . Our short ground baseline measurements ( < ∼ 80 M𝜆) are consistent with an anisotropic Gaussian image, while our intermediate ground baseline measurements (100−250 M𝜆) confirm the presence of persistent image substructure in Sgr A * . Both features are consistent with theoretical expectations for strong scattering in the ionized interstellar medium, which produces Gaussian scatter-broadening on short baselines and refractive substructure on long baselines. We do not detect interferometric fringes on any of the longer ground baselines or on any ground-space baselines. While space VLBI offers a promising pathway to sharper angular resolution and the measurement of key gravitational signatures in black holes, such as their photon rings, our results demonstrate that space VLBI studies of Sgr A * will require sensitive observations at submillimeter wavelengths.

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“…Furthermore, the flux fluctuations caused by the ISS-induced IDV, may have contributed partly to the RA SVLBI observed T b excess (over the IC limit) of blazars [22]. So it is important to find and study the IDV from the blazars in the RA SVLBI observations [23]. In order to search for IDV in the RA sources in parallel with the RA SVLBI sessions, we carried out the IDV observations of the RA sources (plus a few blazars from other samples) with the Urumqi 25 m radio telescope in Xinjiang Astronomical Observatory.…”

Section: Introductionmentioning

confidence: 99%

Intra-Day Variability Observations of Two Dozens of Blazars at 4.8 GHz

et al. 2021

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Two dozens of radio loud active galactic nuclei (AGNs) have been observed with Urumqi 25 m radio telescope in order to search for intra-day variability (IDV). The target sources are blazars (namely flat spectrum radio quasars and BL Lac objects) which are mostly selected from the observing list of RadioAstron AGN monitoring campaigns. The observations were carried out at 4.8 GHz in two sessions of 8–12 February 2014 and 7–9 March respectively. We report the data reduction and the first results of observations. The results show that the majority of the blazars exhibit IDV in 99.9% confidence level, some of them show quite strong IDV. We find the strong IDV of blazar 1357 + 769 for the first time. The IDV at centimeter-wavelength is believed to be predominately caused by the scintillation of blazar emission through the local interstellar medium in a few hundreds parsecs away from Sun. No significant correlation between the IDV strength and either redshift or Galactic latitude is found in our sample. The IDV timescale along with source structure and brightness temperature analysis will be presented in a forthcoming paper.

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Detection statistics of the RadioAstron AGN survey

Cited by 28 publications

References 37 publications

MOJAVE XIX: Brightness Temperatures and Intrinsic Properties of Blazar Jets

MOJAVE XIX: Brightness Temperatures and Intrinsic Properties of Blazar Jets

First Space-VLBI Observations of Sagittarius A*

Intra-Day Variability Observations of Two Dozens of Blazars at 4.8 GHz

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