Open Astronomy最新文献

{"title":"Crossmatching of high-proper motion L, T, and Y brown dwarfs with large photometric surveys","authors":"A. Avdeeva, Sergey V. Karpov, O. Malkov","doi":"10.1515/astro-2022-0214","DOIUrl":"https://doi.org/10.1515/astro-2022-0214","url":null,"abstract":"Abstract L, T, and Y brown dwarf (BD) exploration is a topical issue. First, the transition boundary between planets and BDs is not fully understood yet. Second, there is a phenomenon called the L/T-transition. The observed properties of cooler BDs differ significantly from the less cool ones, namely, colors of BDs shift much bluer and, simultaneously, dwarfs become brighter with a decrease in temperature. Models of this phenomenon are now being actively developed, for which reason BDs observed in a wide range of spectra are needed. Our goal is to refine the position of BDs in the parameter space of colors and magnitudes in order to effectively search for them in photometric surveys (without involving spectroscopic observations). For that reason, we crossmatched about 500 known L, T, and Y BDs with large photometric surveys. We paid special attention to the problem of identifying objects near the Sun because the crossmatching by default is made by searching for the closest object in a particular survey, which can be inappropriate concerning the high proper motions of our dwarfs. We have determined the color indices that can be used to search for these objects in large photometric surveys, and we have pointed out the color indices that are inappropriate for this purpose. We also made preliminary estimates of the radius matching to search for objects in the modern photometric surveys, given their proximity to the Sun and, consequently, their high proper motion.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48045442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ka/C dual frequency ranging system for ocean altimetry satellite and analysis of ionospheric error","authors":"N. Li, Zhenhe Zhai, Jian Ma, Bin Guan, Wenhui Cui, Duan Li","doi":"10.1515/astro-2022-0220","DOIUrl":"https://doi.org/10.1515/astro-2022-0220","url":null,"abstract":"Abstract In view of the future development trend of ocean altimetry satellites, the design idea of Ka/C dual frequency combination system is proposed, that is, the mode of using an altimeter antenna to contain Ka and C frequencies (35.7 and 5.3 GHz, respectively) for combined ranging. First, the random error model of altimeter measuring the distance from the altimeter phase center to the sea surface is given, and the analysis shows that the ionospheric correction error is one of the important factors. Second, the calculation of typical ionospheric parameters shows that the influence of ionospheric higher order terms on altimeter ranging is below the mm level, and its influence can be ignored. The rigorous expression for the first-order and second-order term correction of ionosphere error are given, respectively, by using dual frequency and three frequencies. The computational experiment of Jason-2 and SARAL satellite show that the maximum magnitude of ionospheric error correction in Ku band can reach 11 cm, while the maximum magnitude of ionospheric error correction in Ka band can reach 2 cm. For high-precision applications, ionospheric corrections must be made for single Ka frequency. After Ka/C dual frequency combination is adopted, error correction can be directly conducted without global ionospheric map (GIM) model, and its accuracy will be further improved than GIM model. Under 1 Hz sampling conditions, the ionospheric correction accuracy of Ka/C combination can be better than 2.5 mm, basically eliminating the influence of the ionosphere, and the total ranging accuracy can reach 3.5 cm considering the propagation error.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47440703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Clay minerals and other hydrous alteration products in the Kaba meteorite: Review of the literature and new XRD investigations","authors":"István Viczián, F. Kristály","doi":"10.1515/astro-2022-0213","DOIUrl":"https://doi.org/10.1515/astro-2022-0213","url":null,"abstract":"Abstract The present study is a review of publications regarding special aspects of the mineralogy of the Kaba meteorite, clay minerals, hydrous phases, and organic matter. In Section 1, the history of fall and finding of the meteorite and the first classical mineralogical description in the Year 1961 are mentioned. The most frequent alteration product of primary silicates and the glassy matrix is Fe-bearing saponite. By modelling of hydrothermal alteration of Allende-type meteorites, artificial saponite could be produced. The thermodynamic study proved the possibility of hydrous neoformation of silicates and magnetite at low temperatures, mostly below 100°C. The formation of Fe-rich external rims in forsterite grains by hydrothermal action was demonstrated by electron probe microanalysis and scanning electron microscopy-cathodo-luminescence methods. Foliation in CV3 carbonaceous chondrites indicates that the Kaba meteorite is derived from the external, shallow zone of the parent body. A combination of X-ray power diffraction (XRD) and Mössbauer spectroscopy made the exact modal analysis of CV3 chondrites possible, including Kaba. The study of alteration by in situ determination of stable oxygen isotope contents may provide constraints regarding the oxygen isotopic composition of the aqueous fluid on the CV parent asteroid. The degree of thermal metamorphism of the organic matter was determined by using Raman spectroscopy. The presence of aromatic and aliphatic, saturated and unsaturated hydrocarbons, and various amino acids was demonstrated. The non-biogenic origin is more probable; however, there are textural and mineralogical observations that may indicate also the biogenic origin of organic matter. In addition to the review of the literature above, as an appendix, shortly new XRD investigations of the authors are reported that indicated smectite-like phases in a thin section made of the meteorite.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44794114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An outlier detection method with CNN for BeiDou MEO moderate-energy electron data","authors":"Tian Chao, Cui Ruifei, Zhang Riwei, Xu Peikang, Chen Libo, Shang Jie, Quan Lin, Wan Yujun, Hu Sihui, Yue Fulu, Su Xing","doi":"10.1515/astro-2022-0196","DOIUrl":"https://doi.org/10.1515/astro-2022-0196","url":null,"abstract":"Abstract BeiDou Medium Earth Orbit moderate-energy electron detection data play an important role in space environment effect analysis including satellite anomaly diagnosis, satellite risk estimation, etc. However, the data contain outliers which cause obstacle for the subsequent usage significantly. To solve this problem, we propose an outlier detection method based on convolutional neural networks (CNNs) which can learn a rule from labeled historical data and detect outliers from the detection data. With this method, we can identify outliers and do some follow-up operations to improve the data quality. In comparison with general methods, this CNN method provides a more reliable and rapid way to build dataset for the follow-up work.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":" ","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43282980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An ion beam system for calibration of space low-energy ion detectors","authors":"Shi Guifen, Lian Yiren, Miao Bin, Liu Kai, Hao Xinjun, Pan Zonghao, G. Meng","doi":"10.1515/astro-2022-0225","DOIUrl":"https://doi.org/10.1515/astro-2022-0225","url":null,"abstract":"Abstract Low-energy ion detection in space is one of the most important interests of space exploration. An accurate calibration of this type of instrument is necessary to ensure the effectiveness and scientificness of the obtained data. And the ion source is the most critical equipment in a calibration facility. In this study, an ion beam system based on Kaufman ion source is designed, which can meet the ground calibration of space low-energy ion detection instrument in the low-energy range of 100–1,000 eV. The experimental research shows that when the beam intensity of the ion source is about 100 mA, the Faraday Cup collects about 1 mA of current, and the generated ion beam fluctuates less than 5% within 60 min, which can meet the ground calibration requirements of space low-energy ion detection instruments.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"32 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41330092","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deep learning applications for stellar parameter determination: II-application to the observed spectra of AFGK stars","authors":"M. Gebran, F. Paletou, I. Bentley, Rose Brienza, Kathleen Connick","doi":"10.1515/astro-2022-0209","DOIUrl":"https://doi.org/10.1515/astro-2022-0209","url":null,"abstract":"Abstract In this follow-up article, we investigate the use of convolutional neural network for deriving stellar parameters from observed spectra. Using hyperparameters determined previously, we have constructed a Neural Network architecture suitable for the derivation of T eff {T}_{{rm{eff}}} , log g log g , [ M / H ] left[Mhspace{0.1em}text{/}hspace{0.1em}H] , and v e sin i {v}_{e}sin i . The network was constrained by applying it to databases of AFGK synthetic spectra at different resolutions. Then, parameters of A stars from Polarbase, SOPHIE, and ELODIE databases are derived, as well as those of FGK stars from the spectroscopic survey of stars in the solar neighbourhood. The network model’s average accuracy on the stellar parameters is found to be as low as 80 K for T eff {T}_{{rm{eff}}} , 0.06 dex for log g log g , 0.08 dex for [ M / H ] left[Mhspace{0.1em}text{/}hspace{0.1em}H] , and 3 km/s for v e sin i {v}_{e}sin i for AFGK stars.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"32 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48159783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The specifics of pulsar radio emission","authors":"Boris Ya. Losovsky","doi":"10.1515/astro-2022-0025","DOIUrl":"https://doi.org/10.1515/astro-2022-0025","url":null,"abstract":"A characteristic property of pulsars is pulsed periodic radio emission, which has a high stability of periods. Despite the high stability of the emission periods of pulsars, monitoring the time of arrival of pulses (timing) shows the presence of different types of irregularities: variations of residual deviations, changes in the shape of the pulse, switching on and off of radio emission, and rotation discontinuities. Numerous observations of the radio emission of pulsars indicate that they are caused mainly by processes occurring in the pulsar’s magnetosphere. The special interest causes the observations of a pulsar in the Crab Nebula, performed, in particular, at Jodrell Bank and Pushchino Radio Astronomy Observatory of Lebedev Physical Institute. The connection between the scattering of radio pulses and the measure of the pulsar dispersion, which was established earlier in Pushchino together with Jodrell Bank, has been confirmed. The observed variations in the scattering of radio pulses and their partial correlation with the dispersion measure are explained by the eclipse of the pulsar by plasma clouds with electron density fluctuations significantly exceeding the corresponding fluctuations in the interstellar medium. The question of a possible connection between glitches, dispersion measure variations, radio pulses scattering, and gamma-ray flares is discussed.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"17 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138539012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of the magnetic field on the formation of protostellar disks","authors":"Natalya S. Kargaltseva, Sergey A. Khaibrakhmanov, Alexander E. Dudorov, Sergey N. Zamozdra, Andrey G. Zhilkin","doi":"10.1515/astro-2022-0022","DOIUrl":"https://doi.org/10.1515/astro-2022-0022","url":null,"abstract":"We numerically model the collapse of magnetic rotating protostellar clouds with mass of 10 <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_astro-2022-0022_eq_001.png\" /> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:msub> <m:mrow> <m:mi>M</m:mi> </m:mrow> <m:mrow> <m:mo>⊙</m:mo> </m:mrow> </m:msub> </m:math> <jats:tex-math>{M}_{odot }</jats:tex-math> </jats:alternatives> </jats:inline-formula>. The simulations are carried out with the help of 2D MHD code Enlil. The structure of the cloud at the isothermal stage of the collapse is investigated for the cases of weak, moderate, and strong initial magnetic field. Simulations reveal the universal hierarchical structure of collapsing protostellar clouds, consisting of the flattened envelope with the qausi-magnetostatc disk inside and the first core in its center. The size of the primary disk increases with the initial magnetic energy of the cloud. The magnetic braking efficiently transports the angular momentum from the primary disk into the envelope in the case, when the initial magnetic energy of the cloud is more than 20% of its gravitational energy. The intensity of the outflows launched from the region near the boundary of the first core increases with initial magnetic energy. The “dead” zone with small ionization fraction, <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_astro-2022-0022_eq_002.png\" /> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mi>x</m:mi> <m:mo>&lt;</m:mo> <m:mn>1</m:mn> <m:msup> <m:mrow> <m:mn>0</m:mn> </m:mrow> <m:mrow> <m:mo>−</m:mo> <m:mn>11</m:mn> </m:mrow> </m:msup> </m:math> <jats:tex-math>xlt 1{0}^{-11}</jats:tex-math> </jats:alternatives> </jats:inline-formula>, forms inside the first hydrostatic core and at the base of the outflow. Ohmic dissipation and ambipolar diffusion determine conditions for further formation of the protostellar disk in this region.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"14 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138539021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamics of magnetic flux tubes in accretion disks of Herbig Ae/Be stars","authors":"Sergey A. Khaibrakhmanov, Alexander E. Dudorov","doi":"10.1515/astro-2022-0017","DOIUrl":"https://doi.org/10.1515/astro-2022-0017","url":null,"abstract":"The dynamics of magnetic flux tubes (MFTs) in the accretion disk of typical Herbig Ae/Be star (HAeBeS) with fossil large-scale magnetic field is modeled taking into account the buoyant and drag forces, radiative heat exchange with the surrounding gas, and the magnetic field of the disk. The structure of the disk is simulated using our magnetohydrodynamic model, taking into account the heating of the surface layers of the disk with the stellar radiation. The simulations show that MFTs periodically rise from the innermost region of the disk with speeds up to 10–12 km <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_astro-2022-0017_eq_001.png\" /> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:msup> <m:mrow> <m:mi mathvariant=\"normal\">s</m:mi> </m:mrow> <m:mrow> <m:mo>−</m:mo> <m:mn>1</m:mn> </m:mrow> </m:msup> </m:math> <jats:tex-math>{{rm{s}}}^{-1}</jats:tex-math> </jats:alternatives> </jats:inline-formula>. MFTs experience decaying magnetic oscillations under the action of the external magnetic field near the disk’s surface. The oscillation period increases with distance from the star and initial plasma beta of the MFT, ranging from several hours at <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_astro-2022-0017_eq_002.png\" /> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mi>r</m:mi> <m:mo>=</m:mo> <m:mn>0.012</m:mn> <m:mspace width=\"0.33em\" /> <m:mi mathvariant=\"normal\">au</m:mi> </m:math> <jats:tex-math>r=0.012hspace{0.33em}{rm{au}}</jats:tex-math> </jats:alternatives> </jats:inline-formula> up to several months at <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"graphic/j_astro-2022-0017_eq_003.png\" /> <m:math xmlns:m=\"http://www.w3.org/1998/Math/MathML\"> <m:mi>r</m:mi> <m:mo>=</m:mo> <m:mn>1</m:mn> <m:mspace width=\"0.33em\" /> <m:mi mathvariant=\"normal\">au</m:mi> </m:math> <jats:tex-math>r=1hspace{0.33em}{rm{au}}</jats:tex-math> </jats:alternatives> </jats:inline-formula>. The oscillations are characterized by pulsations of the MFT’s characteristics including its temperature. We argue that the oscillations can produce observed IR-variability of HAeBeSs, which would be more intense than in the case of T Tauri stars, since the disks of HAeBeSs are hotter, denser, and have stronger magnetic field.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"20 1","pages":""},"PeriodicalIF":0.7,"publicationDate":"2022-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138539013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ANALOG-1 ISS – The first part of an analogue mission to guide ESA’s robotic moon exploration efforts","authors":"K. Wormnes, W. Carey, T. Krueger, Leonardo Cencetti, E. D. Exter, Stephen Ennis, Edmundo Ferreira, Antonio Fortunato, L. Gerdes, Lukas Hann, C. Lombardi, E. Luzzi, Sebastian Martin, M. Massironi, S. Payler, Aaron Pereira, A. Rossi, R. Pozzobon, F. Sauro, P. Schoonejans, Frank van der Hulst, J. Grenouilleau","doi":"10.1515/astro-2022-0002","DOIUrl":"https://doi.org/10.1515/astro-2022-0002","url":null,"abstract":"Abstract The European Space Agency’s ANALOG-1 experiment is the culmination of 12 distinct METERON experiments carried out since 2011. These all address aspects of teleoperating a robotic asset from an orbital platform, i.e., technical implementation, user interfaces, autonomy and operations. The ANALOG-1 technology demonstration and operations concept experiment is based upon the surface mission scenario segment of the notional EL3 sample return mission. This segment focuses on the control of a lunar surface robotic asset from the Earth and from the Lunar Gateway. The experiment is taking place in two parts, with the first successfully completed from the ISS in November 2019. It assessed the effectiveness of a state-of-the-art robotic control interface to control a complex mobile robot from orbit, as well as evaluating the scientific interactions, during robotic-assisted geology exploration, between crew in orbit and scientists on the ground. Luca Parmitano operated the robot while he was on the ISS. For this experiment, a complex control station had been installed on the ISS. The experiment demonstrated the advantage of having an immersive control station and high level of robotic dexterity, with Luca finishing all his assigned and secondary geology targets ahead of time.","PeriodicalId":19514,"journal":{"name":"Open Astronomy","volume":"31 1","pages":"5 - 14"},"PeriodicalIF":0.7,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45483130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}