Vsini-s for late-type stars from spectral synthesis in K-band region

We analyse medium-resolution spectra (R\sim 18000) of 19 late type dwarfs in order to determine vsini-s using synthetic rather than observational template spectra. For this purpose observational data around 2.2 $\mu$m of stars with spectral classes from G8V to M9.5V were modelled. We find that the Na I (2.2062 and 2.2090 $\mu$m) and $^{12}$CO 2-0 band features are modelled well enough to use for vsini determination without the need for a suitable observational template spectra. Within the limit of the resolution of our spectra, we use synthetic spectra templates to derive vsini values consistent with those derived in the optical regime using observed templates. We quantify the errors in our vsini determination due to incorrect choice of model parameters \Teff, log $g$, $v_{\rm micro}$, [Fe/H] or FWHM and show that they are typically less than 10 per cent. We note that the spectral resolution of our data(\sim 16 km/s) limited this study to relatively fast rotators and that resolutions of 60000 will required to access most late-type dwarfs.Comment: 8 pages, 4 figures, 3 tables, accepted to the MNRA

Masses, Oxygen and Carbon abundances in CHEPS dwarf stars

Reproduced with permission from Astronomy & Astrophysics. © 2019 ESOContext. We report the results from the determination of stellar masses, carbon, and oxygen abundances in the atmospheres of 107 stars from the Calan-Hertfordshire Extrasolar Planet Search (CHEPS) programme. Our stars are drawn from a population with a significantly super-solar metallicity. At least 10 of these stars are known to host orbiting planets. Aims. In this work, we set out to understand the behaviour of carbon and oxygen abundance in stars with different spectral classes, metallicities, and V sin i within the metal-rich stellar population. Methods. Masses of these stars were determined using data from Gaia DR2. Oxygen and carbon abundances were determined by fitting the absorption lines. We determined oxygen abundances with fits to the 6300.304 Å O I line, and we used 3 lines of the C I atom and 12 lines of the C 2 molecule for the determination of carbon abundances. Results. We determine masses and abundances of 107 CHEPS stars. There is no evidence that the [C/O] ratio depends on V sin i or the mass of the star within our constrained range of masses, i.e. 0.82 5 km s -1) are massive stars.Peer reviewedFinal Published versio

Spots structure and stratification of helium and silicon in the atmosphere of He-weak star HD 21699

The magnetic star HD 21699 possesses a unique magnetic field structure where the magnetic dipole is displaced from the centre by 0.4 +/- 0.1 of the stellar radius (perpendicularly to the magnetic axis), as a result, the magnetic poles are situated close to one another on the stellar surface with an angular separation of 55$^o$ and not 180$^o$ as seen in the case of a centred dipole. Respectively, the two magnetic poles form a large "magnetic spot". High-resolution spectra were obtained allowing He I and Si II abundance variations to be studied as a function of rotational phase. The results show that the helium abundance is concentrated in one hemisphere of the star, near the magnetic poles and it is comparatively weaker in another hemisphere, where magnetic field lines are horizontal with respect to the stellar surface. At the same time, the silicon abundance is greatest between longitudes of 180 - 320$^o$, the same place where the helium abundance is the weakest. These abundance variations (with rotational phase) support predictions made by the theory of atomic diffusion in the presence of a magnetic field. Simultaneously, these result support the possibility of the formation of unusual structures in stellar magnetic fields. Analysis of vertical stratification of the silicon and helium abundances shows that the boundaries of an abundance jump (in the two step model) are similar for each element; $\tau_{5000}$ = 0.8-1.2 for helium and 0.5-1.3 for silicon. The elemental abundances in the layers of effective formation of selected absorption lines for various phases are also correlated with the excitation energies of low transition levels: abundances are enhanced for higher excitation energy and higher optical depth within the applied model atmosphere.Comment: accepted by MN, 7 pagers, 10 figs, 3 table

Communication of COVID-19 consequences in the Baltic States inforsphere

This article seeks to describe the dynamics of COVID-19 in the Baltic States and to analyse the ways of communicating the threat and its consequences. Particular attention is paid to the media strategies pursued in the study area. The research is based on Russian and English texts from the Baltic media, WHO official documents and datasets, as well as initiatives of the Baltic Sea region organisations (2020) counteracting COVID-19. A combination of these sources builds up an objective view of the situation and demonstrates how the pandemic and its consequences are represented in public consciousness given a certain pragmatic goal. The pandemic is a new type of threat; its consequences demonstrate a tendency towards negative synergy and a category shift from soft threats to hard ones. The research shows that several key strategies - counter-active, projective, conservative, mobilising, resilient, and reflective - are used to communicate the threat and its consequences in the media

SDSS J080434.20+510349.2: Eclipsing WZ Sge-Type Dwarf Nova with Multiple Rebrightenings

We observed the 2006 superoutburst of SDSS J080434.20+510349.2 during its plateau phase, rebrightening phase, and post-superoutburst final decline. We found that this object is a grazing eclipsing system with a period of 0.0590048(2) d. Well-defined eclipses were only observed during the late stage of the superoutburst plateau and the depth decreased during the subsequent stages. We determined the superhump period during the superoutburst plateau to be 0.059539(11) d, giving a fractional superhump excess of 0.90(2)%. During the rebrightening and post-superoutburst phases, persisting superhumps with periods longer than those of superhumps during the plateau phase: 0.059632(6) during the rebrightening phase and 0.05969(4) d during the final fading. This phenomenon is very well in line with the previously known long-period "late superhumps" in GW Lib, V455 And and WZ Sge. The amplitudes of orbital humps between different states of rebrightenings suggest that these humps do not arise from the classical hot spot, but are more likely a result of projection effect in a high-inclination system. There was no clear evidence for the enhanced hot spot during the rebrightening phase. We also studied previously reported "mini-outbursts" in the quiescent state and found evidence that superhumps were transiently excited during these mini-outbursts. The presence of grazing eclipses and distinct multiple rebrightenings in SDSS J080434.20+510349.2 would provide a unique opportunity to understanding the mechanism of rebrightenings in WZ Sge-type dwarf novae.Comment: 14 pages, 12 figures, PASJ accepte

Течение COVID-19 у новорожденных

Clinical Infectious Diseases Hospital. S.P. Botkin has been providing assistance to pregnant women and newborns suffering from COVID-19 since the beginning of the pandemic. In the period from April 2020 to April 2022, 550 newborns born to mothers suffering from COVID-19 of varying severity were observed in the hospital, of which 52 children had a registered diagnosis of COVID-19 (the SARS-CoV-2 virus was identified in a swab from the nasopharynx of a newborn using PCR). In this paper, an analysis of the pathological changes identified in this category of newborns was carried out, the issues of the influence of the covid status of the mother and the duration of stay with her on the child’s condition were studied. Analysis of the results of the work revealed a relationship between the duration of the period of stay of a newborn with a mother with an active form of COVID-19 and the severity of the disease in newborns. According to our clinical observations, the vertical route of transmission of the virus seems highly probable. Newborns who have had COVID-19 or have perinatal contact with SARS-CoV-2 are subject to dynamic observation. It is necessary to determine the order, timing and scope of dispensary observation for the timely detection of pathological changes in this category of children.Клиническая инфекционная больница им. С.П. Боткина с начала пандемии оказывает помощь беременным и новорожденным, переносящим COVID-19. В период с апреля 2020 г. по апрель 2022 г. в стационаре наблюдалось 550 новорожденных, родившихся от матерей, переносящих COVID-19 разной степени тяжести, из них 52 ребенка имели зарегистрированный диагноз COVID-19 (вирус SARS-CoV-2 идентифицирован в мазке из носоглотки новорожденного с применением ПЦР). В данной работе проведен анализ патологических изменений, выявленных у данной категории новорождённых, изучены вопросы влияния ковид-статуса матери и длительности пребывания с ней на состояние ребёнка. Анализ результатов работы выявил зависимость между длительностью периода пребывания новорожденного с матерью, имеющей активную форму COVID-19, и тяжестью течения заболевания новорождённых. Вертикальный путь передачи вируса, по нашим клиническим наблюдениям, представляется высоковероятным. Новорожденные, перенесшие COVID-19 или имеющие перинатальный контакт с SARS-CoV-2, подлежат динамическому наблюдению. Необходимо определение порядка, сроков и объёма диспансерного наблюдения для своевременного выявления патологических изменений у данной категории детей

Quasiquarks in two stream system

We study the collective quark excitations in an extremely anisotropic system of two interpenetrating streams of the quark-gluon plasma. In contrast to the gluon modes, all quark ones appear to be stable in such a system. Even more, the quark modes in the two-stream system are very similar to those in the isotropic plasma.Comment: 4 pages, 2 figures, minor corrections, to appear in Phys. Rev.

Collective responses of Bi-2212 stacked junction to 100 GHz microwave radiation under magnetic field oriented along the c-axis

We studied a response of Bi-2212 mesa type structures to 100 GHz microwave radiation. We found that applying magnetic field of about 0.1 T across the layers enables to observe collective Shapiro step response corresponding to a synchronization of all 50 intrinsic Josephson junctions (IJJ) of the mesa. At high microwave power we observed up to 10th harmonics of the fundamental Shapiro step. Besides, we found microwave induced flux-flow step position of which is proportional to the square root of microwave power and that can exceed at high enough powers 1 THz operating frequency of IJJ oscillations.Comment: 11 pages including 5 figures, accepted for publication in JETP Letter