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Frey, S. (author), Zhang, Y. (author), Perger, K. (author), An, T. (author), Gabányi, K. (author), Gurvits, L. (author), Hwang, C. Y. (author), Koptelova, E. (author), Paragi, Z. (author), Fogasy, J. (author)Context. The existence of accreting supermassive black holes of up to billions of solar masses at early cosmological epochs (in the context of this work, redshifts z & 6) requires very fast growth rates that are challenging to explain. The presence of a relativistic jet can be a direct indication of activity and accretion status in active...journal article 2024
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Cho, Ilje (author), Gómez, José L. (author), Lico, Rocco (author), Zhao, Guang Yao (author), Traianou, Efthalia (author), Dahale, Rohan (author), Fuentes, Antonio (author), Toscano, Teresa (author), Gurvits, L. (author)We present total intensity and linear polarization images of OJ 287 at 1.68 GHz, obtained through space-based very long baseline interferometry (VLBI) observations with RadioAstron on April 16, 2016. The observations were conducted using a ground array consisting of the Very Long Baseline Array (VLBA) and the European VLBI Network (EVN)....journal article 2024
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Titov, Oleg (author), Frey, Sándor (author), Melnikov, Alexey (author), Shu, Fengchun (author), Xia, Bo (author), González, Javier (author), Tercero, Belén (author), Gurvits, L. (author), de Witt, Aletha (author)Radio-loud quasars at high redshift (z ≥ 4) are rare objects in the universe and rarely observed with Very Long Baseline Interferometry (VLBI). But some of them have flux density sufficiently high for monitoring of their apparent position. The instability of the astrometric positions could be linked to the astrophysical process in the jetted...journal article 2023
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Gurvits, L. (author), Cimò, Giuseppe (author), Dirkx, D. (author), Pallichadath, V. (author), Altobelli, Nicolas (author), Bocanegra Bahamon, T.M. (author), Cazaux, S.M. (author), Vermeersen, L.L.A. (author), Visser, P.N.A.M. (author)Planetary Radio Interferometry and Doppler Experiment (PRIDE) is a multi-purpose experimental technique aimed at enhancing the science return of planetary missions. The technique exploits the science payload and spacecraft service systems without requiring a dedicated onboard instrumentation or imposing on the existing instrumentation any...review 2023
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Fletcher, Leigh N. (author), Cavalié, Thibault (author), Grassi, Davide (author), Hueso, Ricardo (author), Lara, Luisa M. (author), Kaspi, Yohai (author), Galanti, Eli (author), Gurvits, L. (author), Cazaux, S.M. (author)ESA’s Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the...review 2023
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Kim, Jae Young (author), Savolainen, Tuomas (author), Voitsik, Petr (author), Kravchenko, Evgeniya V. (author), Lisakov, Mikhail M. (author), Kovalev, Yuri Y. (author), Müller, Hendrik (author), Gurvits, L. (author), Lee, S. (author)We present results from the first 22 GHz space very long baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in 2014 February at 22 GHz with 21 ground stations, reaching projected (u, v) spacings up to ∼11 Gλ. The imaging experiment was...journal article 2023
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Nunes, N. V. (author), Bartel, N. (author), Belonenko, A. (author), Manucharyan, G. D. (author), Rudenko, V. N. (author), Gurvits, L. (author), Cimò, G. (author), Molera Calvés, G. (author), Zakhvatkin, M. V. (author)The Einstein Equivalence Principle (EEP) is a cornerstone of general relativity and predicts the existence of gravitational redshift. We report on new results of measuring this shift with RadioAstron (RA), a space very long baseline interferometry (VLBI) spacecraft launched into an evolving high eccentricity orbit around Earth with geocentric...journal article 2023
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Fayolle-Chambe, M.S. (author), Lainey, V. (author), Dirkx, D. (author), Gurvits, L. (author), Cimo, G. (author), Bolton, S. J. (author)Context. Stellar occultations currently provide the most accurate ground-based measurements of the positions of natural satellites (down to a few kilometres for the Galilean moons). However, when using these observations in the calculation of satellite ephemerides, the uncertainty in the planetary ephemerides dominates the error budget of the...journal article 2023
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Benke, P. (author), Gabányi, K. E. (author), Frey, S. (author), An, T. (author), Gurvits, L. (author), Kun, E. (author), Mohan, P. (author), Paragi, Z. (author), Ros, E. (author)Context. PSO J334.2028+1.4075 (PSO J334) is a luminous quasar located at redshift z = 2.06. The source gained attention when periodic flux density variations were discovered in its optical light curve. These variations were initially interpreted as the variability due to the orbital motion of a supermassive black hole binary (SMBHB) residing...journal article 2023
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Frey, Sándor (author), An, Tao (author), Gabányi, Krisztina (author), Gurvits, L. (author), Krezinger, Máté (author), Melnikov, Alexey (author), Mohan, Prashanth (author), Paragi, Zsolt (author), Perger, Krisztina (author)The powerful high-redshift quasar J2102+6015 (at z = 4.575) may provide useful information for studying supermassive black hole growth, galaxy evolution and feedback in the early Universe. The source has so far been imaged with very-long-baseline interferometry (VLBI) at 2/8 GHz (S/X) bands only, showing complex compact structure. Its total...journal article 2023
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Perger, Krisztina (author), Zhang, Yingkang (author), Frey, Sándor (author), An, Tao (author), Gabányi, Krisztina E. (author), Gurvits, L. (author), Hwang, Chorng Yuan (author), Koptelova, Ekaterina (author), Paragi, Zsolt (author), Wang, Ailing (author)There are approximately 250 quasars discovered at redshift z ≥ 6, of which only a handful were detected in radio bands, and even fewer were imaged with the highest resolution very long baseline interferometry (VLBI) technique. Here we report the results of our dual-frequency observations with the Very Long Baseline Array (VLBA) of two such...journal article 2023
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Hudson, Ben (author), Gurvits, L. (author), Wielgus, Maciek (author), Paragi, Zsolt (author), Liu, Lei (author), Zheng, Weimin (author)Recent advances in technology coupled with the progress of observational radio astronomy methods resulted in achieving a major milestone of astrophysics - a direct image of the shadow of a supermassive black hole, taken by the Earth-based Event Horizon Telescope (EHT). The EHT was able to achieve a resolution of ∼20μas, enabling it to resolve...journal article 2023
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Yang, Jun (author), Paragi, Zsolt (author), Frey, Sándor (author), Gurvits, L. (author), Liao, Mai (author), Liu, Xiang (author), Cui, Lang (author), Yang, Xiaolong (author), Chen, Wen (author)Dwarf galaxies are characterized by a very low luminosity and low mass. Because of significant accretion and ejection activity of massive black holes, some dwarf galaxies also host low-luminosity active galactic nuclei (AGNs). In a few dwarf AGNs, very long baseline interferometry (VLBI) observations have found faint non-thermal radio...journal article 2023
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Yan, Jingye (author), Wu, Ji (author), Gurvits, L. (author), Wu, Lin (author), Deng, Li (author), Zhao, Fei (author), Zhou, Li (author), Lan, Ailan (author), Fan, Wenjie (author)This paper introduces the first results of observations with the Ultra-Long-Wavelength (ULW) —- Low Frequency Interferometer and Spectrometer (LFIS) on board the selenocentric satellite Longjiang-2. We present a brief description of the satellite and focus on the LFIS payload. The in-orbit commissioning confirmed a reliable operational status...journal article 2023
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Gabanyi, K.E. (author), Belladitta, S. (author), Frey, S. (author), Orosz, G. (author), Gurvits, L. (author), Rozgonyi, Krisztina (author), An, T. (author), Cao, H (author), Paragi, Z (author), Perger, Krisztina (author)Active galactic nuclei (AGN) have been observed as far as redshift. They are crucial in investigating the early Universe as well as the growth of supermassive black holes at their centres. Radio-loud AGN with their jets seen at a small viewing angle are called blazars and show relativistic boosting of their emission. Thus, their apparently...journal article 2023
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Gómez, José L. (author), Traianou, Efthalia (author), Krichbaum, Thomas P. (author), Lobanov, Andrei P. (author), Fuentes, Antonio (author), Lico, Rocco (author), Zhao, Guang Yao (author), Bruni, Gabriele (author), Gurvits, L. (author)We present the first polarimetric space very long baseline interferometry (VLBI) observations of OJ 287, observed with RadioAstron at 22 GHz during a perigee session on 2014 April 4 and five near-in-time snapshots, together with contemporaneous ground VLBI observations at 15, 43, and 86 GHz. Ground-space fringes were obtained up to a...journal article 2022
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Krezinger, Máté (author), Perger, Krisztina (author), Gabányi, Krisztina Éva (author), Frey, Sándor (author), Gurvits, L. (author), Paragi, Zsolt (author), An, Tao (author), Zhang, Yingkang (author), Cao, Hongmin (author), Sbarrato, Tullia (author)High-redshift radio sources provide plentiful opportunities for studying the formation and evolution of early galaxies and supermassive black holes. However, the number of known radio-loud active galactic nuclei (AGN) above redshift 4 is rather limited. At high redshifts, it appears that blazars, with relativistically beamed jets pointing...journal article 2022
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Zhang, Y. (author), An, T. (author), Wang, A. (author), Frey, S. (author), Gurvits, L. (author), Gabányi, K. E. (author), Perger, K. (author), Paragi, Z. (author)The nature of jets in active galactic nuclei (AGNs) in the early Universe and their feedback to the host galaxy remains a highly topical question. Observations of the radio structure of high-redshift AGNs enabled by very long baseline interferometry (VLBI) provide indispensable input into studies of their properties and role in the galaxies'...journal article 2022
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Gurvits, L. (author), Falcke, Heino (author), Frey, Sándor (author), Fromm, Christian M. (author), García-Miró, Cristina (author), Janssen, Michael (author), Masania, K. (author), Rajan, R.T. (author), Visser, P.N.A.M. (author)Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI...journal article 2022
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Yang, Jun (author), Yang, Xiaolong (author), Wrobel, Joan M. (author), Paragi, Zsolt (author), Gurvits, L. (author), Ho, Luis C. (author), Nyland, Kristina (author), Fan, Lulu (author), Tafoya, Daniel (author)NGC 4395 is a dwarf galaxy at a distance of about 4.3 Mpc (scale: ∼0.021 pc mas-1). It hosts an intermediate-mass black hole (IMBH) with a mass between ∼104 and ∼105 solar masses. The early radio observations of NGC 4395 with the very long baseline interferometry (VLBI) network, High Sensitivity Array (HSA), at 1.4 GHz in 2005 showed that its...journal article 2022