Astronomical and Astrophysical Transactions最新文献

{"title":"Receiver gain and system temperature instability during the calibration of spectral data at radio telescopes in C-band","authors":"O. Antyufeyev, M. Bleiders, O. Patoka, V. Bezrukovs, A. Aberfelds, I. Shmeld, A. Orbidans, J. Šteinbergs, Y. Karelin, V. Shulga","doi":"10.17184/eac.6474","DOIUrl":"https://doi.org/10.17184/eac.6474","url":null,"abstract":"The errors arising at the calibration of spectral data from single-dish observations at the radio telescopes of C-band are considered. It was assumed that errors arise as a result of the instability of the receiver gain and system temperature. Theoretical formula for the relative error of the antenna temperature of the source is obtained. Simulation of the calibration process was carried out to verify this formula. The process of observation of methanol masers at the frequency of 6.7 GHz at the Irbene RT-32 radio telescope (Ventspils) was reproduced during simulation. The errors of the antenna temperature of the source arising from observations are estimated.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"127 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85356675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of intra-day variability of the radio galaxy 3C 84 (Perseus A) flux density in centimeter range on the RT-32 VIRAC (Latvia) and RT-32 NSFCTC (Ukraine) radio telescopes","authors":"A. Sukharev, M. Ryabov, V. Bezrukovs, A. Orbidans","doi":"10.17184/eac.6477","DOIUrl":"https://doi.org/10.17184/eac.6477","url":null,"abstract":"Extragalactic radio source 3C 84 (also known as Perseus A) is the active nucleus of the giant galaxy NGC 1275, the largest in the Perseus galaxy cluster (Abell 426). It is one of the brightest X-ray galaxy clusters. The nucleus of galaxy NGC 1275 (Seyfert II type) is a powerful radio source in the Northern Sky (flux density at frequency 8 GHz is about 30 Jy). 3C 84 has a long-term variability in the radio band, with a “wave-like” change in the flux density on a time scale of several decades. The purpose of our work was to search for and study the properties and features of the appearance of fast variability of the 3C 84 radio source in the centimeter radio range. For this, as part of the international Ukrainian–Latvian cooperation between the Institute of Radio Astronomy NAS of Ukraine and the Ventspils International Radio Astronomy Centre, many observation sessions were performed (October 2020 – September 2021) at the 32-m radio telescopes in Ukraine (Zolochiv) and Latvia (Irbene), with additional observations at the 16-m radio telescope (Irbene). As a result, the following main results were obtained: the 3C 84 radio source exhibits manifestations of episodic intraday variability, with characteristic times, usually in the range 3–8 hours, as well as “calm phases”, when there is no significant variability, and the source flux density does not change over several observation sessions. The most likely cause of this variability could be interstellar scintillations, but some quasi-simultaneous observations of 3C 84 carried out at the 32-m radio telescopes in Ukraine and Latvia showed the presence of a correlation in cross-Fourier spectra, with a characteristic time about 6 hours. In addition, the appearance of 3C 84 flux variability with characteristic times from 1–3 hours to several tens of minutes were recorded, which were not associated with radiointerference or hardware effects. They were detected in observations both in Ukraine and in Latvia, in different seasons of the year.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"os-41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87231981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Prediction of cometary OH maser emission in 1.6 GHz frequency band based on optical brightness","authors":"K. Šķirmante, G. Jasmonts","doi":"10.17184/eac.6476","DOIUrl":"https://doi.org/10.17184/eac.6476","url":null,"abstract":"Cometary OH maser emission evaluation was carried out to identify potentially bright comets for which OH maser emission were detectable in 1.6 GHz frequency range using Irbene RT-32 radio telescope. The evaluation model was based on the results of more than 3320 comets observations using data from optical and radio observations. Using the evaluation model, the correlation between optical brightness and radio flux density and correlation between flux density and OH production models was analyzed. In the research a prediction neural network model prototype was created to predict the comet brightness value in optical frequency range, based on the analyzed results from obtained correlation and characteristics of the comet. Based on the prediction model, the comet C/2021 A1 (Leonard) was observed in 1.6 GHz frequency band using Irbene RT-32 radio telescope. Spectral analysis using Fourier transform was applied to radio astronomical data from multiple observations related to weak cometary OH maser detection.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"70 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86048922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Probable connection between the drag of the International Space Station and various indexes that determine the state of space weather in 23–24 solar activity cycles","authors":"V. H. Komendant","doi":"10.17184/eac.6467","DOIUrl":"https://doi.org/10.17184/eac.6467","url":null,"abstract":"The analysis of the ISS’s drag data during the period from 2005 to 2019 was carried out. In the analysis the B-star drag term was applied. This coefficient reflects the influence of changes in the state of the atmosphere on the movement of artificial objects in the Earth’s orbit. The time periods of the ISS movement when significant adjustments they were not made to the station’s orbit and the reception of planned missions were selected. The analysis of changes in the ISS’s drag was carried out. Data of solar and geomagnetic activity, including episodes of strong drag and periods of regular changes were used.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90623182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Results of comparison of fast variations of geomagnetic field and ionospheric scintillations of 3C 144 radio source in the area of Odessa geomagnetic anomaly","authors":"A. Sukharev, M. Orlyuk, M. Ryabov, L. Sobitniak, V. Bezrukovs, S. Panishko, A. Romenets","doi":"10.17184/eac.6481","DOIUrl":"https://doi.org/10.17184/eac.6481","url":null,"abstract":"From November 2017 to May 2019 at the Astronomical Observatory of Odessa I.I. Mechnikov National University, the variational component of the geomagnetic field was monitored to study short-periodic geomagnetic variations in the central part of the Odessa regional magnetic anomaly. The measurements were carried out using a LEMI-008 precision fluxgate magnetometer with a sampling rate of 1 Hz. The aim of this work is to compare the manifestation of short-periodic geomagnetic oscillations (which in some cases coincided with periods of geomagnetic pulsations) and ionospheric scintillations of the 3C 144 radio source (Taurus A) according to the data of URAN-4 low-frequency phased antenna array at frequencies of 20 and 25 MHz. The data obtained were processed on a daily basis using the method of continuous wavelet transform, as well as band-pass filtering based on Fourier transform, to select individual frequency bands containing irregular and quasi-harmonic variations in the geomagnetic field and radio flux density. The analysis of results of the observations, during geomagnetic disturbances, storms and in calm conditions, is carried out. The data from long-term monitoring of variational component of the geomagnetic field in the most interesting, central part of the Odessa magnetic anomaly, where such studies have not been conducted before, have been obtained. Observations of various manifestations of ionospheric scintillations were carried out both during magnetic storms and during a calm geomagnetic field. It is shown that during storms, main scintillation time scale of the 3C 144 radio source is 1–3 minutes. Ionospheric scintillations occasionally show a quasiperiodic structure.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84253247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Results of studying the radio and optical variability properties of MRK 501 active galaxy","authors":"A. Sukharev, M. Ryabov, V. Bezrukovs, O. Ulyanov, S. Udovichenko, L. Keir, P. Dubovský, I. Kudzej, A. Konovalenko, V. Zakharenko, I. Eglitis, V. Tsehmeystrenko, D. Bakun","doi":"10.17184/eac.6469","DOIUrl":"https://doi.org/10.17184/eac.6469","url":null,"abstract":"MRK 501 is a giant radio galaxy with an active core in the constellation Hercules. It is a powerful gamma source. MRK 501 has gamma cyclic variability as well as high X-ray and optical activity. MRK 501 is a quite powerful variable radio source, with a flux density at 15 GHz about 1.2 Jy. Of particular interest is the presence of cyclic brightness variations in gamma and optical ranges, which, according to modern models, may be caused by the presence of a supermassive double black hole in the core of the galaxy MRK 501. In this work, optical observatories of three countries, Ukraine (Mayaki, Heavenly Owl), Slovakia (Vihorlat) and Latvia (Baldone), took part in a joint project to study the rapid variability of AGN in radio and optical bands. The analysis of observations obtained from different observatories in V , R, I bands showed the presence of a wave-like, presumably cyclic, variability in the light curves with an average quasi-period of 46.7 days. Taking into account that a quasi-period of about 23 days was detected in the gamma range, it is most likely that we have found a harmonic (doubled value) of this period in the optical range, which is a new result. In addition, an analysis of long-term variability of MRK 501, from historical light curves of the AAVSO catalog, showed the presence of two longer cycles of variability with quasiperiods of about 1 year and about 5–6 years. It is shown that these quasi-periods, as well as their amplitudes, are unevenly distributed over an observation time interval from 2003 to 2021 (18 years) and change significantly over time.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80389640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On one property of the movement on the outskirts of the Solar System","authors":"O. Bazyey, N. Bazyey","doi":"10.17184/eac.6465","DOIUrl":"https://doi.org/10.17184/eac.6465","url":null,"abstract":"A numerical simulation of the equipotential surfaces of the gravitational field in the immediate vicinity of the Solar System has been performed taking into account gravitational perturbations from the Galactic tide and 355 stars closest to the Sun. It is demonstrated that at certain values of the gravitational potential energy, the Sun shares the equipotential surface with Toliman (Alpha Centauri B), Sirius and Procyon. The use of a method of numerical integration of the equations of motion of 150 test bodies has shown instability of circular orbits with a radius of 60,000 au about the Sun.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77692496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"On the perspectives for separating the radio flux variations of the nucleus and the jet of active galactic based on data from monitoring programs and VLBI observations","authors":"D. Zabora, M. Ryabov, A. Sukharev, M. Petrenko","doi":"10.17184/eac.6470","DOIUrl":"https://doi.org/10.17184/eac.6470","url":null,"abstract":"The subject and purpose of the work: the possibility of separating the spectral flux densities of the active core and the jet of sources (3C 120, 3C 273, 3C 345, 3C 454.3, 3C 446, Bl Lac, CTA 102, OJ 287, OT 081) is considered. The data of long-term monitoring of changes in the integral flux of extragalactic radio sources performed on the 26-meter telescope of the University of Michigan UMRAO (1969–2012) at frequencies of 14.5, 8, 4.8 GHz are used. Also, data on the core flux and images of active galactic nuclei at a frequency of 15–15.4 GHz VLBA monitoring MOJAVE are used. The subject of this work is to separate the jet flow from the integral flux from the source, as well as to compile the catalog of the quasi-periods of variability of nuclei and jets separately. Methods and methodology: Fourier-periodogram analysis is used to distinguish long-term and short-period variability of nuclei and jets of extragalactic sources. Autocorrelation calculations were carried out in order to confirm the periods of variability. Results: conclusions were made about the applicability of the described method for separating the jet flux, and a catalog of long-term and short-period variability of radio emission fluxes from nuclei and jets for the investigated radio sources was compiled.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89409159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tidal phenomena in the Earth’s upper atmosphere","authors":"M. Ryabov, L. Sobitniak","doi":"10.17184/eac.6468","DOIUrl":"https://doi.org/10.17184/eac.6468","url":null,"abstract":"From 1987 to the present, the radio flux of powerful galactic and extragalactic radio sources is monitored at decameter waves at the URAN-4 radio telescope of the Odessa Observatory of the Radio Astronomy Institute of the National Academy of Sciences of Ukraine. The work is based on revealing the nature of unusual records of radio sources that were not associated with the presence of interference in the decameter radio band. Changes of fluxes of radiation sources at decameter waves are determined by the condition of an ionosphere as a result of variation in space weather and tidal events. When radio sources are observed through a tidal wave, a “plasma lens” effect is realized in the ionosphere. Depending on the position of the radio source relative to the tidal wave, the radiation wave front is sought. As a result, various effects are realized: strong focusing, intense flickering or “blurred” recording of the radio source. This effect was originally reflected in earlier works [1]. In this paper the analog records of radio sources (1987-1990) and digital (1998-2004) are considered and various tidal effects were clarified. Based on the results of measurements, the angular dimensions of the tidal wave, reaching 60 degrees, were determined. Radio astronomy observations in the decameter range at the URAN-4 radio telescope are an effective method for studying tidal phenomena in the Earth's upper atmosphere.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89311274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Towards the density of matter","authors":"O. Gerasymov, L. S. Kudashkina","doi":"10.17184/eac.6466","DOIUrl":"https://doi.org/10.17184/eac.6466","url":null,"abstract":"We discuss some visible analogies of mapping of the density of matter field which has been observed in Universe and in particular in micro-mechanical granular materials. In both of the mentioned global classes of physical systems the same known initial problem exists: the local density field is insufficiently defined. Several structural characters which are in common in those, quite differently scaled systems (like specific clusterisation), are outlined.\u0000\u0000The observed external similarity of clustering, characterized by the formation of specific filamentous clusters, both in granular matter and in the distribution of matter in the Universe allows the model level to use the granular phase parameterization scenario (compaction parameter instead of density) in the study of distribution of matter in the Universe.","PeriodicalId":52135,"journal":{"name":"Astronomical and Astrophysical Transactions","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85086360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}