RadioAstron Science Program Five Years after Launch: Main Science Results

Kardashëv, N. S.; Alakoz, A. V.; Andrianov, A. S.; Artyukhov, M. I.; Baan, Willem A.; Babyshkin, V.; Bartel, N.; Bayandina, O. S.; Вальтц, И. Е.; Voitsik, P. A.; Vorobyov, A. Z.; Gwinn, C. R.; Gómez, J. L.; Giovannini, G.; Jauncey, D. L.; Johnson, Michael D.; Imai, Hiroshi; Kovalev, Y. Y.; Kurtz, S.; Lisakov, M. M.; Lobanov, A. P.; Molodtsov, V. A.; Novikov, B.; Pogodin, A. V.; Попов, М. В.; Privesenzev, A. S.; Rudnitski, A. G.; Rudnitski, G. M.; Savolainen, Tuomas; Smirnova, T. V.; Sobolev, A. M.; Soglasnov, V. A.; Sokolovsky, K. V.; Filippova, E. N.; Хартов, В. В.; Churikova, M. E.; Shirshakov, A. E.; Shishov, V. I.; Edwards, P. G.

doi:10.1134/s0038094617070085

Cited by 30 publications

(13 citation statements)

References 22 publications

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“…If flow velocities are underestimated, it may explain the extreme brightness temperatures observed e.g. by RadioAstron Gómez et al 2016;Kardashev et al 2017;Pilipenko et al 2018;Kutkin et al 2018b) and significantly alter various other estimates of jet parameters. Variability of the core position reported above can provide an independent way to estimate the plasma speed in the jet.…”

Section: Opacity Changes In the Core And Jet Flow Velocitymentioning

confidence: 99%

Significant core shift variability in parsec-scale jets of active galactic nuclei

Plavin

Kovalev

Pushkarev

et al. 2019

Monthly Notices of the Royal Astronomical Society

103

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The apparent position of jet base (core) in radio-loud active galactic nuclei changes with frequency because of synchrotron self-absorption. Studying this 'core shift' effect enables us to reconstruct properties of the jet regions close to the central engine. We report here results from core shift measurements in AGNs observed with global VLBI at 2 and 8 GHz at epochs from 1994 to 2016. Our sample contains 40 objects observed at least 10 times during that period. The core shift is determined using a new automatic procedure introduced to minimize possible biases. The resulting multiple epoch measurements of the core position are employed for examining temporal variability of the core shift. We argue that the core shift variability is a common phenomenon, as established for 33 of 40 AGNs we study. Our analysis shows that the typical offsets between the core positions at 2 and 8 GHz are about 0.5 mas and they vary in time. Typical variability of the individual core positions is about 0.3 mas. The measurements show a strong dependence between the core position and its flux density, suggesting that changes in both are likely related to the nuclear flares injecting denser plasma into the flow. We determine that density of emitting relativistic particles significantly increases during these flares, while relative magnetic field changes less and in the opposite direction.

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Section: Opacity Changes In the Core And Jet Flow Velocitymentioning

confidence: 99%

Significant core shift variability in parsec-scale jets of active galactic nuclei

Plavin

Kovalev

Pushkarev

et al. 2019

Monthly Notices of the Royal Astronomical Society

103

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“…The most recent space-Earth VLBI has been implemented in Radioastron space mission, which is a 10 meter space radio telescope, that has been successfully operating for more than 7 years (Kardashev et al 2013(Kardashev et al , 2015(Kardashev et al , 2017. Radioastron formed a space-Earth interferometer together with up to 60 ground telescopes at four frequencies: 0.3 GHz, 1.6 GHz, 4.8 GHz and 22 GHz.…”

Section: Millimetron Missionmentioning

confidence: 99%

Simulations of M87 and Sgr A* Imaging with the Millimetron Space Observatory on near-Earth orbits

Andrianov,

Baryshev,

Falcke

et al. 2020

Preprint

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High resolution imaging of supermassive black holes shadows is a direct way to verify the theory of general relativity at extreme gravity conditions. Very Long Baseline Interferometry (VLBI) observations at millimeter/sub-millimeter wavelengths can provide such angular resolution for supermassive black holes, located in Sgr A* and M87. Recent VLBI observations of M87 with the Event Horizon Telescope (EHT) has shown such capabilities. The maximum obtainable spatial resolution of EHT is limited by Earth diameter and atmospheric phase variations. In order to improve the image resolution longer baselines are required. Radioastron space mission has successfully demonstrated the capabilities of Space-Earth VLBI with baselines much larger than Earth diameter. Millimetron is a next space mission of the Russian Space Agency that will operate at millimeter wavelengths. Nominal orbit of the observatory will be located around Lagrangian L2 point of the Sun-Earth system. In order to optimize the VLBI mode, we consider a possible second stage of the mission that could use near-Earth high elliptical orbit (HEO). In this contribution a set of near Earth orbits is used for the synthetic space-ground VLBI observations of Sgr A* and M87 in joint Millimetron and EHT configuration. General-relativistic magnetohydrodynamic models (GRMHD) for black hole environment of Sgr A* and M87 are used for static and dynamic imaging simulations at 230 GHz. A comparison is made between ground and space-ground baselines. It demonstrates that joined observations with Millimetron and EHT facilities significantly improve the image resolution and allow obtaining the dynamic snapshot images of Sgr A*.

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“…Currently, the mission has been operating for more than 7 years already, conducting daily space-ground VLBI observations [7]. It has four frequency bands: 0.327 GHz (P-band), 1.665 GHz (L-band), 4.830 GHz (C-band) and 18.392-25.112 GHz (K-band) and is capable of observing at two bands simultaneously.…”

Section: Radioastron Missionmentioning

confidence: 99%

The Current and Future of Ground and Space-VLBI Science.

Rudnitskiy¹,

Лихачев²,

Andrianov³

et al. 2019

Proceedings of Frontier Research in Astrophysics – III — PoS(FRAPWS2018)

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Very Long Baseline Interferometry (VLBI) has been developing for more than half a century and came to a new level after the emergence of the possibility to launch radio telescope into space. Radioastron mission that is led by Astro Space Center was launched in July, 2011 and currently is the only 10-m space radio telescope operating for more than 6 years. It operates as a Space-Earth interferometer together with more than 40 ground telescopes, observing pulsars, masers, AGN&QSO sources with the highest angular resolution. Millimetron is the next space observatory of Astro Space Center to be addressed for the far infrared, sub-millimeter and millimeter wavelength ranges. The unprecedented sensitivity and angular resolution of the cooled 10-m telescope, operating in a L2 orbit, will provide the astronomical community an opportunity to solve key scientific problems in astronomy and astrophysics. The observatory will have two observing modes: Space-Earth VLBI element and single dish telescope.

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RadioAstron Science Program Five Years after Launch: Main Science Results

Cited by 30 publications

References 22 publications

Significant core shift variability in parsec-scale jets of active galactic nuclei

Significant core shift variability in parsec-scale jets of active galactic nuclei

Simulations of M87 and Sgr A* Imaging with the Millimetron Space Observatory on near-Earth orbits

The Current and Future of Ground and Space-VLBI Science.

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