Multi-element Doppler imaging of the CP2 star HD 3980

In atmospheres of magnetic main-sequence stars, the diffusion of chemical elements leads to a number of observed anomalies, such as abundance spots across the stellar surface. The aim of this study was to derive a detailed picture of the surface abundance distribution of the magnetic chemically peculiar star HD 3980. Based on high-resolution, phase-resolved spectroscopic observations of the magnetic A-type star HD 3980, the inhomogeneous surface distribution of 13 chemical elements (Li, O, Si, Ca, Cr, Mn, Fe, La, Ce, Pr, Nd, Eu, and Gd) has been reconstructed. The INVERS12 code was used to invert the rotational variability in line profiles to elemental surface distributions. Assuming a centered, dominantly dipolar magnetic field configuration, we find that Li, O, Mg, Pr, and Nd are mainly concentrated in the area of the magnetic poles and depleted in the regions around the magnetic equator. The high abundance spots of Si, La, Ce, Eu, and Gd are located between the magnetic poles and the magnetic equator. Except for La, which is clearly depleted in the area of the magnetic poles, no obvious correlation with the magnetic field has been found for these elements otherwise. Ca, Cr, and Fe appear enhanced along the rotational equator and the area around the magnetic poles. The intersection between the magnetic and the rotational equator constitutes an exception, especially for Ca and Cr, which are depleted in that region. No obvious correlation between the theoretically predicted abundance patterns and those determined in this study could be found. This can be attributed to a lack of up-to-date theoretical models, especially for rare earth elements.Comment: 1o pages, accepted by A&

Effects of spot structure of lines of rare earths and non-LTE effects on lithium abundance estimates for two roAp stars

Taking into account blending of the lithium 6108 Å line profile by adjacent rare-earth lines together with their spotted surface structure does not appreciably affect lithium abundance estimates for the atmospheres of HD 83368 and HD 60435 but provides a better fit of the observed and stimulated line profiles. Our computed non-LTE corrections reduce the lithium abundance estimates by 0.1-0.2 dex for both stars. Given the uncertainties in the lithium abundances, it is not possible to be certain whether the lithium abundances in map stars, or at least in their spots, exceed the cosmic (primordial) value. © 2002 MAIK "Nauka/Interperiodica"

Lithium and its isotopic ratio 6Li/7Li in the atmospheres of some sharp-lined roAp star

The lines of lithium at 6708 A, and 6103 A, are analyzed in high resolution spectra of some sharp-lined and slowly rotating roAp stars. Three spectral synthesis codes - STARSP, ZEEMAN2 and SYNTHM were used. New lines of the rare earth elements from the DREAM database, and lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. Enhanced abundances of lithium in the atmospheres of the stars studied are obtained for both the lithium lines. High estimates of 6Li/7Li ratio (0.2 -- 0.5) for the studied star can be explained by Galactic Cosmic Ray (GCR) production through the spallation reactions and the preservation of the original $^6$Li and $^7$Li by the strong magnetic fields.Comment: 5 pages, 2*5 figs, submitted for IAUS #224 Proceeding

Lithium and its isotopic ratio ⁶Li/⁷Li in the atmospheres of sharp-lined roAp stars γ Equulei and HD 166473

The lithium lines at 6708 Å for two sharp-lined roAp stars γ Equ and HD 166473 and at 6103 Å for γ Equ were analyzed in high resolution spectra. Three spectral synthesis codes – STARSP, ZEEMAN2, and SYNTHM – were used. New lines of the rare-earth elements from the DREAM database and lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. Enhanced abundances of lithium in the atmospheres of the stars and high estimates of ⁶Li/⁷Li ratio (0.2 ÷ 0.5) can be explained by the Galactic Cosmic Ray (GCR) production due to spallation reactions and the preservation of original ⁶Li and ⁷Li by strong magnetic fields

Photometry of ET Andromedae and pulsation of HD 219891

ET And is a binary system with a B9p(Si) star as the main component. We report on the photometric observing campaigns in 1988, 1989 and 1994 which confirmed the rotation period of 1(.)(d)618875 for ET And while refuting other published values. Furthermore, the controversial issue of pulsational stability of ET And is resolved since we have discovered pulsation for HD 219891, which was the main comparison star and sometimes exclusively used. The frequency of 10.0816 d(-1), a semi-amplitude of 2.5 mmag, T(eff) and M(v) suggest this comparison star to be a delta Scuti variable close to the blue border of the instability strip. The pulsational stability of ET And could be clearly established and hence no need exists to derive new driving mechanisms for stars between the classical instability strip and the region of slowly pulsating B-type (SPB) stars

Оптимизация условий пробоподготовки для ионохроматографического определения хлорид-ионов, входящих в состав высокомолекулярных органических соединений нефти

A procedure of sample preparation of oil samples for the determination of chloride ions, which are part of high-molecular organic compounds, has been developed. The procedure consists in the extraction of chloride ions from oil into the aqueous phase with a solution of sodium nitrate, followed by ionochromatographic detection. The work was performed on a high-performance LC‑20 Prominence liquid chromatograph with LC Solution software (Shimadzu, Japan), equipped with a conductometric detector (CDD‑10 Avp/10Asp), a 120×5 mm KanK-ASt14 μm separating column (GEOHI RAS, Russia) and a 200×6 mm SPS-SAC 50 suppression column μm (LLC PC «Aquilon», Russia). A carbonate buffer solution (2.5 mM Na2CO3 + 3.0 mM NaHCO3) was used as an eluent. The volume of the injected sample is 100 μl. The eluent flow rate was 2.0 ml/min. The temperature of the column thermostat is 33 °C. Under these conditions, satisfactory separation of fluoride, chloride, nitrate, and sulfate ions is achieved, and hydrogen sulfide does not have ionic forms and does not manifest ionochromatographically. Using the method of full factorial experiment, the main parameters determining the efficiency of extraction of chloride ions from the organic phase were optimized: extraction of 1 mM with an aqueous solution of NaNO3 at a temperature of 90 ± 2 °C, the volume ratio of oil and extractant 1:10, extraction time 20 min. The developed procedure of sample preparation has been tested on model solutions and real oil samples. In comparison with the known methods, the combination of extraction isolation of organic chlorides with ionochromatographic detection makes it possible to significantly simplify the procedure for determining the analyte due to the high selectivity of the method without loss in sensitivity and measurement accuracyРазработан способ пробоподготовки образцов нефти для определения хлорид-ионов, входящих в состав высокомолекулярных органических соединений. Способ заключается в экстракционном выделении хлорид-ионов из нефти в водную фазу раствором нитрата натрия с их последующим ионохроматографическим детектированием. Работу выполняли на высокоэффективном жидкостном хроматографе LC‑20 Prominence с программным обеспечением LC Solution (Shimadzu, Япония), укомплектованным кондуктометрическим детектором (CDD‑10 Avp/10Asp), разделяющей колонкой 120×5 мм КанК-АСт14 мкм (ГЕОХИ РАН, Россия) и подавительной колонкой 200×6 мм СПС-SAC 50 мкм (ООО ПК «Аквилон», Россия). В качестве элюента применяли карбонатный буферный раствор (2,5 мМ Na2CO3 + 3,0 мМ NaHCO3). Объем вводимой пробы 100 мкл. Скорость потока элюента составляла 2,0 мл/мин. Температура термостата колонки 33 °C. В данных условиях достигается удовлетворительное разделение фторид-, хлорид-, нитрат-, сульфат- ионов, а сероводород не имеет ионных форм и ионохроматографически не проявляется. С использованием метода полного факторного эксперимента оптимизированы основные параметры, определяющие эффективность извлечения хлорид-ионов из органической фазы: экстракция 1мМ водным раствором NaNO3 при температуре 90±2 °C, объемное соотношение нефти и экстрагента 1:10, время экстрагирования 20 мин. Разработанный способ пробоподготовки апробирован на модельных растворах и реальных образцах нефти. По сравнению с известными методами сочетание экстракционного выделения органических хлоридов с ионохроматографическим детектированием позволяет существенно упростить процедуру определения аналита за счет высокой селективности метода без потери в чувствительности и точности измерени