Context.
Despite being the best studied red supergiant star in our Galaxy, the physics behind the photometric variability and mass loss of Betelgeuse is poorly understood. Moreover, recently the star ...has experienced an unusual fading with its visual magnitude reaching a historical minimum. The nature of this event was investigated by several studies where mechanisms, such as episodic mass loss and the presence of dark spots in the photosphere, were invoked.
Aims.
We aim to relate the atmospheric dynamics of Betelgeuse to its photometric variability, with the main focus on the dimming event.
Methods.
We used the tomographic method which allowed us to probe different depths in the stellar atmosphere and to recover the corresponding disk-averaged velocity field. The method was applied to a series of high-resolution HERMES observations of Betelgeuse. Variations in the velocity field were then compared with photometric and spectroscopic variations.
Results.
The tomographic method reveals that the succession of two shocks along our line-of-sight (in February 2018 and January 2019), the second one amplifying the effect of the first one, combined with underlying convection and/or outward motion present at this phase of the 400 d pulsation cycle, produced a rapid expansion of a portion of the atmosphere of Betelgeuse and an outflow between October 2019 and February 2020. This resulted in a sudden increase in molecular opacity in the cooler upper atmosphere of Betelgeuse and, thus, in the observed unusual decrease of the star’s brightness.
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A novel species is proposed for a high-affinity methanotrophic representative of the genus
. Strain FS
was isolated from a weakly acidic (pH 5.3) mixed forest soil of the southern Moscow area. Cells ...of FS
are aerobic, Gram-negative, non-motile, curved coccoids or short rods that contain an intracytoplasmic membrane system typical of type-II methanotrophs. Only methane and methanol are used as carbon sources. FS
grew at a temperature range of 4-37 °C (optimum 25-30 °C) and a pH range of 4.5 to 7.5 (optimum pH 6.0-6.5). The major fatty acids were C
ω8
, C
ω7
and C
; the major quinone as Q-8. FS
displays 16S rRNA gene sequences similarity to other taxonomically recognized members of the genus
with
CSC1
(99.6 % similarity) and
SV97
(99.3 % similarity) as its closest relatives. The genome comprises 3.85 Mbp and has a DNA G+C content of 62.6 mol%. Genomic analyses and DNA-DNA relatedness with genome-sequenced members of the genus
demonstrated that FS
could be separated from its closest relatives. FS
possesses two particulate methane monooxygenases (pMMO): low-affinity pMMO1 and high-affinity pMMO2. In laboratory experiments, it was demonstrated that FS
might oxidize methane at atmospheric concentration. The genome contained various genes for nitrogen fixation, polyhydroxybutyrate synthesis, antibiotic resistance and detoxification of arsenic, cyanide and mercury. On the basis of genotypic, phenotypic and chemotaxonomic characteristics, it is proposed that the isolate represents a novel species,
sp. nov. The type strain is FS
(=KCTC 82935
=VKM B-3535
).
Red supergiants are the most common final evolutionary stage of stars that have initial masses between 8 and 35 times that of the Sun
. During this stage, which lasts roughly 100,000 years
, red ...supergiants experience substantial mass loss. However, the mechanism for this mass loss is unknown
. Mass loss may affect the evolutionary path, collapse and future supernova light curve
of a red supergiant, and its ultimate fate as either a neutron star or a black hole
. From November 2019 to March 2020, Betelgeuse-the second-closest red supergiant to Earth (roughly 220 parsecs, or 724 light years, away)
-experienced a historic dimming of its visible brightness. Usually having an apparent magnitude between 0.1 and 1.0, its visual brightness decreased to 1.614 ± 0.008 magnitudes around 7-13 February 2020
-an event referred to as Betelgeuse's Great Dimming. Here we report high-angular-resolution observations showing that the southern hemisphere of Betelgeuse was ten times darker than usual in the visible spectrum during its Great Dimming. Observations and modelling support a scenario in which a dust clump formed recently in the vicinity of the star, owing to a local temperature decrease in a cool patch that appeared on the photosphere. The directly imaged brightness variations of Betelgeuse evolved on a timescale of weeks. Our findings suggest that a component of mass loss from red supergiants
is inhomogeneous, linked to a very contrasted and rapidly changing photosphere.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
An experimental estimation of the high efficiency of restoring fatigue strength and durability of prototypes and hinged-bolted joints' eyes made of high-strength 30KHGSN2A steel by repeated peening ...by shot in a multi-cycle region is given. The results obtained take into account the effects of stress concentration and the statistical nature of the fatigue failure process on the recovery level and increase cyclic durability.
Context. Red supergiants are cool massive stars and are the largest and the most luminous stars in the Universe. They are characterized by irregular or semi-regular photometric variations, the ...physics of which is not clearly understood. Aims. The paper aims to derive the velocity field in the red supergiant star μ Cep and to relate it to the photometric variability with the help of the tomographic method. Methods. The tomographic method allows one to recover the line-of-sight velocity distribution over the stellar disk and within different optical-depth slices. This method was applied to a series of high-resolution spectra of μ Cep, and these results are compared to those obtained from 3D radiative-hydrodynamics CO5BOLD simulations of red supergiants. Fluctuations in the velocity field are compared with photometric and spectroscopic variations, the latter were derived from the TiO band strength and serve, at least partly, as a proxy of the variations in effective temperature. Results. The tomographic method reveals a phase shift between the velocity and spectroscopic and photometric variations. This phase shift results in a hysteresis loop in the temperature – velocity plane with a timescale of a few hundred days, which is similar to the photometric one. The similarity between the hysteresis loop timescale measured in μ Cep and the timescale of acoustic waves disturbing the convective pattern suggests that such waves play an important role in triggering the hysteresis loops.
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Purpose. To conduct an analysis of the spread of contemporary globalization processes and the geo-ecological problems caused by them, directions regulating the development of cities in the aspect of ...the concept of sustainable development; to single out and justify the geoecological problems of cities on the basis of the analysis of the development of global urbanization processes.
Methods. Given the interdisciplinary nature of the research, the work uses systemic, synergistic, and historical scientific approaches, as well as a complex of scientific methods: methods of induction and deduction, the method of comparison, the method of generalization, the method of analogy, the method of systematization, and the method of modeling.
Results. The development and implementation of the Concept of sustainable development, the aspects of sustainable urbanization were determined based on the study of the formation of the world scientific opinion on the issue of sustainable development, namely: environmental protection, economic development, social justice and equality. Their components and the concept of "sustainable urbanization" were considered. The presentation of various aspects of sustainable urbanization in the development programs of the World Bank, UN-Habitat and the Alliance of Cities, in particular – geoecological one, was analyzed. The peculiarities of the flow of geoecological problems of cities and the need to take this aspect into account for the sustainable development of urban social and geographical systems were substantiated.
Conclusions. The obtained results demonstrate significant attention to the geoecological aspect of urbanization, the importance of its research and analysis in the aspect of sustainable development of cities. An important aspect of further strategic planning and development of cities is a harmonious combination of ecological, economic and social components. In further research, the author plans to develop a model of sustainable development of the city with a balanced ratio of economic, social and environmental components of development.
Purpose. Improving the principles of management of photovoltaic system with storage battery and with autonomous functioning during daylight hours for a local object, connected to the grid with ...multi-zone payment when excluding the generation of energy into the grid. Methodology. Modeling and analysis of energy processes in the photovoltaic system was performed using the Matlab software package. The simulation model of energy processes is based on calculated expressions taking into account the characteristics of the battery. Operability of the proposed solutions are confirmed on an experimental setup based on a standard hybrid inverter. Results. It’s shown, that due to the battery energy during the most loaded peak hours and part of the daytime the system operates autonomously and does not depend on possible violations of the quality of electricity in the grid. Scenarios of the recommended load schedule are proposed in accordance with the ratio of the predicted value of the daily energy generation of the photovoltaic battery to its possible maximum value. A simulation model of energy processes in the system with the correction of the recommended load value was developed. Originality. A method of the recommended load calculation with current correction for the actual generation and degree of battery charge is proposed, which allows taking into account differences the actual generation of the photovoltaic battery from its predicted value and the actual load from the recommended one. Practical value. The obtained solutions are the basis for the design of new and modernization of existing photovoltaic systems of local objects using software and hardware complexes for power consumption management.
Calculation and experimental methods for evaluating the cyclic crack resistance of materials and plain workpieces after hardening their surface layer by various technological processes are presented ...and argued. These methods can be used in engineering calculations to determine and designate the most effective processes for surface hardening of parts from high-strength materials and to optimize process parameters.
Distribution function of the maximum values of voltage overload cycles in some aircraft parts is proposed. Based on the data from the flight experiment, more than 100 records of random load case ...processes were schematized and processed statistically. The proposed model of the distribution of maximum load cycles and processed experimental data has been verified.
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