"Stellar Prominences" on OB stars to explain wind-line variability

Many O and B stars show unexplained cyclical variability in their winds, i.e. modulation of absorption features on the rotational timescale, but not strictly periodic over longer timescales. For these stars no dipolar magnetic fields have been detected, with upper limits below 300 G. Similar cyclical variability is also found in many optical lines, which are formed at the base of the wind. We propose that these cyclical variations are caused by the presence of multiple, transient, short-lived, corotating magnetic loops, which we call "stellar prominences". We present a simplified model representing these prominences to explain the cyclical optical wind-line variability in the O supergiant lambda Cephei. Other supporting evidence for such prominences comes from the recent discovery of photometric variability in a comparable O star, which was explained by the presence of multiple transient bright spots, presumably of magnetic origin as well.Comment: Contributed paper IAUS 302, Biarritz, August 2013, 4 pages, 3 figure

Flora differentiation among local ecotopes in the transzonal study of forest-steppe and steppe mounds

Flora similarity was assessed using complete floristic lists of five ecotopes in each of four mounds along the transect from meadow steppes to desert steppes. It was found that the circumapical similitude of floras is more significant than the expositional similitude. Soil analysis in separate ecotopes showed that regular changes in the biogeochemical features are manifested along the topographic gradient and under the effect of the insolation exposure of slopes in local (mound) ecosystem

Railway transportation as a serious source of organic and inorganic pollution

Polycyclic aromatic hydrocarbons and heavy metal (Pb, Cd, Cu, Zn, Hg, Fe, Co, Cr, Mo) contents were established in soil and plant samples collected in different areas of the railway junction Iława Główna, Poland. Soil and plant samples were collected in four functional parts of the junction, i.e. the loading ramp, main track within platform area, rolling stock cleaning bay and the railway siding. It was found that all the investigated areas were strongly contaminated with polycyclic aromatic hydrocarbons (PAHs). The PAH contamination of the soil was the highest in the railway siding and in the platform area (59,508 and 49,670 μg kg−1, respectively). In the loading ramp and cleaning bay, the PAH concentration in soil was lower but still relatively very high (17,948 and 15,376 μg kg−1, respectively). The contamination in the railway siding exceeded the average control level up to about 80 times. In the soil of all the investigated areas, four- and five-ring PAHs prevailed. The concentrations of PAHs were determined in four dominating species of plants found at the junction. The highest concentration was found in the aerial parts of Taraxacum officinale (22,492 μg kg−1) growing in the cleaning bay. The comparison of the soil contamination with PAHs in the investigated railway junction showed a very significant increase of the PAHs level since 1995. It was found that the heavy metal contamination was also very high. Pb, Zn, Hg and Cd were established at the highest levels in the railway siding area, whereas Fe concentration was the highest in the platform area. A significant increase in mercury content was observed in the cleaning bay area. The investigations proved very significant increase of contamination with PAHs and similar heavy metals contamination in comparison with the concentration determined in the same areas 13 years ago

ВЛИЯНИЕ ИНКРУСТАЦИИ СЕМЯН СМЕСЯМИ N-ФОСФОНОМЕТИЛГЛИЦИНА И ЭПИБРАССИНОЛИДА НА РОСТ РАСТЕНИЙ

The dependence of action of an inhibitory dose of N-phosphonomethylglycine mixed with epibrassinolide over a wide concentration range, on the root growth of flax (Linum usitatissimum L.) and barley (Hordeum vulgare L.) seedlings is studied. Specific and varietal specificity of growth responses to the incrustation of seeds by such mixtures is identified. The epibrassinolide concentration range, in which its interaction with N-phosphonomethylglycine is most expressed, is detected. It is characterized by the intensification (in spring barley seedlings) or the weakening (in flax seedlings) of the inhibitory effect of glyphosate on the root system.Исследована зависимость действия N-фосфонометилглицина в ингибирующей дозе в смеси с эпибрассинолидом в широком диапазоне концентраций на рост корневой системы проростков льна-долгунца (Linum usitatissimum L.) и ярового ячменя (Hordeum vulgare L.). Установлена видовая и сортовая специфичность ростовых реакций на обработку семян такими смесями. Обнаружен диапазон концентраций эпибрассинолида, в котором его взаимодействие с N-фосфонометилглицином выражено максимально, что характеризуется усилением (на проростках ярового ячменя) либо ослаблением (на проростках льна-долгунца) ингибирующего эффекта глифосата на корневую систему

Ultraviolet spectropolarimetric diagnostics of hot star magnetospheres

peer reviewe

X-Shooting ULLYSES: Massive stars at low metallicity: I. Project description

Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational wave events involving spectacular black hole mergers indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observing ∼250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES programme. The complementary X-Shooting ULLYSES (XShootU) project provides an enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESOa's Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates as a function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of astrophysics, the data and modelling of the XShootU project is expected to be a game changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb Space Telescope spectra of the first stellar generations, the individual spectra of low-Z stars need to be understood, which is exactly where XShootU can deliver

Ultraviolet spectropolarimetry with Polstar: using Polstar to test magnetospheric mass-loss quenching

peer reviewe

Spectropolarimetry of stars across the H-R diagram

The growing sample of magnetic stars shows a remarkable diversity in the properties of their magnetic fields. The overall goal of current studies is to understand the origin, evolution, and structure of stellar magnetic fields in stars of different mass at different evolutionary stages. In this chapter we discuss recent measurements together with the underlying assumptions in the interpretation of data and the requirements, both observational and theoretical, for obtaining a realistic overview of the role of magnetic fields in various types of stars.Comment: 23 pages, 3 figures, chapter 7 of "Astronomical Polarisation from the Infrared to Gamma Rays", published in Astrophysics and Space Science Library 46