Article
Astronomy & Astrophysics
K. Ross, N. Hurley-Walker, N. Seymour, J. R. Callingham, T. J. Galvin, M. Johnston-Hollitt
Summary: Characterizing the spectral variability of radio sources can help determine the physical processes involved and provide evidence to support absorption models. In this study, we observed 15 peaked-spectrum sources with the Australia Telescope Compact Array and the Murchison Widefield Array, and found that the variability at megahertz frequencies is mainly caused by refractive interstellar scintillation. We also identified sources with changes in spectral shape, possibly due to variable optical depth or jet ejections.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
K. Ross, J. R. Callingham, N. Hurley-Walker, N. Seymour, P. Hancock, T. M. O. Franzen, J. Morgan, S. White, M. E. Bell, P. Patil
Summary: Studies of spectral variability for a large population of extragalactic radio sources are now possible, with variability more prevalent in peaked-spectrum sources. Observations suggest that the radio sky in the megahertz regime is more dynamic than previously suggested.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Chemistry, Analytical
Victor Puente, Marta Folgueira
Summary: VLBI is the only technique to directly determine celestial pole offsets. This study uses VLBI data to correct main lunisolar nutation terms in the IAU 2006/2000A precession-nutation model, finding that the choice of celestial reference frame and stochastic model can have a small effect on the estimated corrections.
Article
Astronomy & Astrophysics
Jun Yang, Yongjun Chen, Leonid Gurvits, Zsolt Paragi, Aiyuan Yang, Xiaolong Yang, Zhiqiang Shen
Summary: In this study, the authors found a catalogue of 39 variable radio sources and analyzed 17 of them using very-long-baseline interferometric imaging technique. They identified a diverse nature of these sources based on their spectral and structural properties.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Patrick M. Yates-Jones, Ross J. Turner, Stanislav S. Shabala, Martin G. H. Krause
Summary: In this study, a method is proposed to apply spatially resolved adiabatic and radiative loss processes to synthetic radio emission from hydrodynamic simulations of radio sources from active galactic nuclei (AGNs). The study finds a strong dependence of radio source properties on frequency and redshift, with asymmetric spectral indices in different environments. Additionally, when jets disrupt before reaching the tip of the lobe, a specific morphology is retained.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
N. G. Simion, M. Popescu, J. Licandro, O. Vaduvescu, J. de Leon, R. M. Gherase
Summary: This study examined the spectral characteristics of near-Earth objects with low Jupiter-Tisserand invariant values, revealing that 56.2% exhibit comet-like spectral features, with a higher prevalence for objects with T-J <= 2.8.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Chemistry, Analytical
Sadegh Modiri, Robert Heinkelmann, Santiago Belda, Zinovy Malkin, Mostafa Hoseini, Monika Korte, Jose M. Ferrandiz, Harald Schuh
Summary: Studying the correlation between CPM and GMF variations can enhance the understanding of the contribution of the Earth's rotation parameters, which is crucial for achieving the accuracy goals of Earth orientation parameters.
Article
Multidisciplinary Sciences
Thomas Kronland-Martinet, Leo Poughon, Marcel Pasquinelli, David Duche, Julien R. Serres, Stephane Viollet
Summary: Navigation can be done using celestial polarization and other natural cues. By observing celestial rotation or measuring skylight polarization, the direction and position can be determined.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2023)
Article
Astronomy & Astrophysics
Pratik Dabhade, Gopal-Krishna
Summary: We accurately determined the 'spectral index-flux density relation' (alpha-S) for extragalactic radio sources selected at different wavelengths using recent survey data. The relation shows a progressive flattening of alpha towards lower flux densities, resolving a long-standing controversy in the literature. The relation is less sharply peaked at lower wavelengths due to the presence of very steep spectrum sources associated with clusters of galaxies.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Khaled Alielden
Summary: Understanding the generation mechanism of stripes-pattern radio spectra is important for studying the dynamics of non-thermal electrons in astronomical objects like the Sun, Jupiter, and the Crab Pulsar. This study conducts an analytical investigation to identify the plasma characteristics of fiber- and zebra-pattern emission sources. The results show that the magnetic field in the zebra-pattern emission source is weak compared to the fiber-pattern emission source. The study also provides a computational approach to estimate the plasma parameters of a zebra-pattern emission source and investigates the behavior of the blasted medium produced by magnetic reconnection.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Multidisciplinary Sciences
Renu Malhotra, Takashi Ito
Summary: The unusual properties of Pluto's orbit provide evidence for the orbital migration of giant planets in the early solar system. However, some properties remain enigmatic. This study investigates the gravitational effects of the giant planets on Pluto's orbit and finds that the latitudinal constraint is possible due to the orbital architecture of other giant planets. Additionally, Jupiter has a stabilizing influence while Uranus has a destabilizing influence on Pluto's orbit. Overall, Pluto's orbit is surprisingly close to a zone of strong chaos.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Geosciences, Multidisciplinary
C. M. McKenna, A. C. Maycock
Summary: The study using the Multimodel Large Ensemble Archive found that two-thirds of the spread in late 21st century projections of the winter North Atlantic Oscillation (NAO) can be explained by model structural differences, rather than by NAO itself. Therefore, improving understanding of the NAO alone may not constrain the reducible uncertainty in North Atlantic mean sea level pressure (MSLP) projections.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Astronomy & Astrophysics
Sandeep Kumar Mondal, Raj Prince, Nayantara Gupta, Avik Kumar Das
Summary: A detailed study of the blazar PKS 0903-57 was conducted based on 12 years of Fermi Large Area Telescope data, revealing two bright gamma-ray flares in 2018 and 2020. Analysis of substructures within the flares yielded estimates for variability timescale, magnetic field, and jet power. Further simultaneous multiwavelength monitoring is needed for a better understanding of the physical processes in the blazar's jet.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
J. Katz
Summary: Repeating and apparently non-repeating fast radio bursts (FRBs) are qualitatively different and may be produced by different sources. Although apparently non-repeating FRBs should repeat multiple times in their lifetimes, no infrequent repetitions have been observed so far. They are associated with outbursts of soft gamma repeaters (SGRs), but with lower energy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Oceanography
Junlu Li, Jianping Gan
Summary: The study investigates the subsurface circulation system in the western North Pacific and reveals the characteristics and formation mechanism of the Luzon Undercurrent (LUC). The LUC transport shows weak seasonality and strong intra-seasonal variation, and its origin is closely connected with the Deep North Equatorial Current (DNEC) and the South China Sea Intermediate Water. The appearance of the LUC is dynamically linked with the sea surface height gradient and the downward tilting of the zonal isopycnal off the Philippine coast. The core of the LUC shifts from in-shore to off-shore waters spatially.
JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
(2022)
Article
Engineering, Aerospace
Yu. A. Kovalev, N. S. Kardashev, Y. Y. Kovalev, K. V. Sokolovsky, P. A. Voitsik, P. G. Edwards, A. V. Popkov, G. V. Zhekanis, Yu. V. Sotnikova, N. A. Nizhelsky, P. G. Tsybulev, A. K. Erkenov, N. N. Bursov
ADVANCES IN SPACE RESEARCH
(2020)
Article
Astronomy & Astrophysics
P. H. T. Tam, P. S. Pal, Y. D. Cui, N. Jiang, Y. Sotnikova, C. W. Yang, L. Z. Wang, B. T. Tang, Y. B. Li, J. Mao, A. K. H. Kong, Z. H. Zhong, J. Ding, T. Mufakharov, J. F. Fan, L. M. Dou, R. F. Shen, Y. L. Ai
JOURNAL OF HIGH ENERGY ASTROPHYSICS
(2020)
Article
Astronomy & Astrophysics
Hao Peng, Zhongzu Wu, Bo Zhang, Yongjun Chen, Xingwu Zheng, Dongrong Jiang, Zhiqiang Shen, Xi Chen, Yu Sotnikova
ASTRONOMY & ASTROPHYSICS
(2020)
Article
Astronomy & Astrophysics
A. G. Mikhailov, Yu Sotnikova
Summary: This paper presents observation results of 33 FR0 radio galaxies in the local universe, showing that they dominate compact radio sources and have flat, complex spectra with high opacity and multiple components contributing to the total spectrum. Additionally, a statistically significant correlation was found between parsec scale jet power and bolometric luminosity of the accretion disk. New candidates for sources with spectral peaks in the GHz range were identified, and 44% of objects exhibited peaked-shaped spectral profiles.
Article
Astronomy & Astrophysics
Yulia Sotnikova, Timur Mufakharov, Marat Mingaliev, Alexander Mikhailov
Summary: This study reports the radio continuum properties of several peaked spectrum (PS) radio sources, discussing statistical differences among various AGN types and focusing on high redshift (z>3) PS quasars. It confirms that only a small fraction of bright PS sources can be considered genuine gigahertz-peaked spectrums (GPSs) with dense and long-term monitoring, and highlights the contamination of GPS source samples by blazars, which is underestimated due to lack of systematic multifrequency observations.
ASTRONOMISCHE NACHRICHTEN
(2021)
Article
Astronomy & Astrophysics
Alexander Mikhailov, Yulia Sotnikova
Summary: This study examines the relationship between FR0 radio galaxies and GPS sources, suggesting a potential connection between them. Analysis of radio spectra indicates that most FR0 objects have broader spectra than genuine GPS sources, with some demonstrating significant variability. The findings suggest a possible link between FR0 objects and blazars.
ASTRONOMISCHE NACHRICHTEN
(2021)
Article
Astronomy & Astrophysics
Yu Sotnikova, Zhongzu Wu, T. Mufakharov, A. G. Mikhailov, M. G. Mingaliev, A. K. Erkenov, T. A. Semenova, N. N. Bursov, R. Y. Udovitskiy, V. A. Stolyarov, P. G. Tsybulev, Y. J. Chen, J. S. Zhang, Z. Shen, D. R. Jiang
Summary: The study found that the OH megamaser sample has more flat-spectrum sources and both samples are dominated by steep radio spectra. There is a strong correlation between far-infrared and radio luminosities in the OHM sample. Differences in FIR and radio properties between masers powered by AGNs and star formation were found to be insignificant.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Yu Sotnikova, A. Mikhailov, T. Mufakharov, M. Mingaliev, N. Bursov, T. Semenova, V Stolyarov, R. Udovitskiy, A. Kudryashova, A. Erkenov
Summary: This study presents the radio properties of optically selected quasars with redshifts greater than or equal to 3, showing that bright high-redshift quasars commonly exhibit a peaked spectral shape and high radio loudness. Several new candidates for megahertz-peaked spectrum (MPS) and gigahertz-peaked spectrum (GPS) were suggested, requiring further research and additional low-frequency observations for precise classification.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Hong Wu, Zhongzu Wu, Yu Sotnikova, Yongjun Chen, Bo Zhang, T. Mufakharov, Zhiqiang Shen, Xi Chen, A. Mikhailov, M. Mingaliev, Xianming L. Han, Prabhakar Misra
Summary: Based on the analysis of data from IIZw 096, this study confirms the high-resolution OH emission mainly comes from the D1 component of the merging system, and the environment does not show clear velocity structure. The brightness temperature of the OH megamaser is consistent with a starburst origin according to radio continuum observations.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Yu. V. Sotnikova, T. V. Mufakharov, A. G. Mikhailov, V. A. Stolyarov, Z. Z. Wu, M. G. Mingaliev, T. A. Semenova, A. K. Erkenov, N. N. Bursov, R. Y. Udovitskiy
Summary: This study investigates the radio variability of galaxies with and without OH megamaser radiation. It estimates the variability index and finds that the radio variability of galaxies with and without OH emission is moderate and of the same order of magnitude on long time scales. The study also determines the spectral index and color temperatures of dust components and finds no statistically significant differences in the distribution of these parameters between the two samples.
ASTROPHYSICAL BULLETIN
(2022)
Article
Astronomy & Astrophysics
Yingkang Zhang, Tao An, Sandor Frey, Krisztina Eva Gabanyi, Yulia Sotnikova
Summary: This paper presents evidence and parameter estimates for high-redshift jets in radio quasars with a redshift range of z > 3.5. The results show that the apparent speeds of these jets do not exceed 20 times the speed of light, consistent with earlier studies.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Zhongzu Wu, Yu. V. Sotnikova, Bo Zhang, T. Mufakharov, Ming Zhu, Peng Jiang, Yongjun Chen, Zhiqiang Shen, Chun Sun, Hao Peng, Hong Wu
Summary: In this study, we investigate the radio continuum and OH line emission of OH megamaser (OHM) galaxies with z >= 0.15. Our findings reveal that the OH emission is distributed in a compact structure and is associated with the radio continuum emission. The obtained results suggest that the OH line profiles of these sources originate from one masing region or multiple components on small scales. Additionally, our analysis of the radio parameters suggests that the presence of a radio active galactic nucleus in the nuclei may not be essential for the formation of OH emission.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Tao An, Ailing Wang, Yuanqi Liu, Yulia Sotnikova, Yingkang Zhang, J. N. H. S. Aditya, Sumit Jaiswal, George Khorunzhev, Baoqiang Lao, Ruqiu Lin, Alexander Mikhailov, Marat Mingaliev, Timur Mufakharov, Sergey Sazonov
Summary: Jets may have played a role in the growth of seed black holes in the early Universe, making observations of radio-loud high-redshift quasars important for understanding the growth and evolution of supermassive black holes. In this study, the radio properties of a bright X-ray quasar at z=5.5, J1702+1301, were examined. A radio counterpart was detected at the optical position of J1702+1301, as well as another radio component associated with a foreground galaxy. After removing contamination from the foreground source, the radio loudness of J1702+1301 was recalculated to be consistent with blazars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Yu. V. Sotnikova, T. V. Mufakharov, M. G. Mingaliev, R. Y. Udovitskiy, T. A. Semenova, A. K. Erkenov, N. N. Bursov, A. G. Mikhailov, Yu. V. Cherepkova
Summary: This paper presents the updated version of the RATAN-600 multi-frequency catalogue of BL Lacertae objects, which now includes flat-spectrum radio quasars (FSRQs). The catalogue provides radio continuum data for blazars at various frequencies and additional data from external sources for a more comprehensive study. Tools for calculating spectral index, variability index, and radio luminosity are also developed for user convenience. The paper briefly describes the basic radio properties of different types of blazars in the catalogue.
ASTROPHYSICAL BULLETIN
(2022)
Article
Astronomy & Astrophysics
T. Mufakharov, A. Mikhailov, Yu Sotnikova, M. Mingaliev, V Stolyarov, A. Erkenov, N. Nizhelskij, P. Tsybulev
Summary: This paper reports the first detection of the source PSO J047.4478+27.2992, identified as a blazar at z=6.1, using the RATAN-600 radio telescope at 4.7 and 8.2 GHz. The source shows moderate variability and a single power-law radio spectrum, consistent with high-redshift quasars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
