Abundances of carbon,nitrogen, oxygen,and other elements in the atmospheres of the giants 25 Mon and HR 7389

An analysis of high-resolution CCD spectra of the giant 25 Mon, which shows signs of metallicity, and the normal giant HR 7389 is presented. The derived effective temperatures, gravitational accelerations, and microturbulence velocities are T_eff = 6700 K, log g = 3.24, and ξ _t = 3.1 km/s for 25 Mon and T_eff = 6630 K, log g = 3.71, and ξ _t = 2.6 km/s for HR 7389. The abundances (log ε) of nine elements are determined: carbon, nitrogen, oxygen, sodium, silicon, calcium, iron, nickel, and barium. The derived excess carbon abundances are 0.23 dex for 25 Mon and 0.16 dex for HR 7389. 25 Mon displays a modest (0.08 dex) oxygen excess, with the oxygen excess for HR 7389 being somewhat higher (0.15 dex). The nitrogen abundance is probably no lower than the solar value for both stars. The abundances of iron, sodium, calcium (for HR 7389), barium, and nickel exceed the solar values by 0.22–0.40 dex for both stars. The highest excess (0.62 dex) is exhibited by the calcium abundance for 25 Mon. Silicon displays a nearly solar abundance in both stars—small deficits of ?0.03 dex and ?0.07 dex for 25 Mon and HR 7389, respectively. No fundamental differences in the elemental abundances were found in the atmospheres of 25 Mon and HR 7389. Based on their T_eff and log g values, as well as theoretical calculations, A. Claret estimated the masses, radii, luminosities, and ages of 25 Mon (M/M_⊙ = 2.45, log(R/R_⊙) = 0.79, log(L/L_⊙) = 1.85, t = 5.3 × 10⁸ yr) and HR 7389 (M/M_⊙ = 2.36, log(R/R_⊙) = 0.50, log(L/L_⊙) = 1.24, t = 4.6 × 10⁸ yr), and also of the stars 20 Peg (M/M_⊙ = 2.36, log(R/R_⊙) = 0.73, log(L/L_⊙) = 1.79, t = 4.9 × 10⁸ yr) and 30 LMi (M/M_⊙ = 2.47, log(R/R_⊙) = 0.73, log(L/L_⊙) = 1.88, t = 4.8 × 10⁸ yr) studied by the author earlier.     

Model atmospheres of red giants

Techniques and results of computations of model atmospheres are discussed for M and C giants and for giants with abundance anomalies. The SAM12 code, a modification of the ATLAS12 code developed by Kurucz, is used. Blanketing effects due to atomic and molecular line absorption are taken into account using the opacity-sampling approach. The computed model atmosphere for the Sun (G2V) is used as a test of the SAM12 code. The model red-giant atmospheres are compared with models reported in other studies. Comparisons between the computed and observed spectral energy distributions are given for the C giant WX Cyg (C-J6) and Sakurai's object (V4334 Sgr).     

Elemental abundances in atmospheres of cool dwarfs with solar-like activity

The elemental abundances in the atmosphere of the red dwarf HD 32147, which belongs to the HR 1614 moving groups, are analyzed. The atmospheric parameters determined from spectroscopic data (the condition of equal abundances for neutral and ionized atoms of a given element) differ considerably from those derived from photometry and parallax data. The abundances of several elements are also anomalous, with the anomaly increasing with decreasing ionization potential. It is concluded that this star is a red dwarf displaying solar-like activity; i.e., having dark (cool) spots on its surface, which may sometimes be considerable in size. Modeling synthetic spectra of stars with cool spots on their surfaces, with the spectral lines consisting of two components formed in media with different temperatures, indicate that the spectroscopic atmospheric parameters derived in such cases are incorrect; this can also explain the observed dependence of the elemental abundances on the corresponding ionization potentials. This leads to the conclusion thatHD32147 is indeed a star with solar-like activity. Several other such stars considered as examples display the same anomalies as those of HD 32147. These modeling results are also valid for Ap and Am stars, and are able to explain short-wavelength observations of the Sun and some stars (the FIP effect).     

Analysis of elemental abundances in the atmospheres of three Hyades red giants

Model atmospheres are fitted to spectroscopic data in order to analyze the elemental abundances in the atmospheres of three red giants in the Hyades cluster. The three stars have almost identical chemical compositions, with iron-group elements slightly overabundant compared to the solar values—a pattern that is typical of Hyades dwarfs. The overabundances of the light elements Na, Al, and Si are virtually equal to those observed for field giants. No enrichment in rare-earth elements relative to iron was found, in sharp contrast to field giants. It is concluded that these discrepancies are due to the age difference between the two groups of stars, which have resulted in different degrees of convective overshooting.     

Peculiarities of the abundances of neutron-capture elements in Galactic open clusters

The properties of the relative abundances of rapid and slow neutron-capture elements are studied using a catalog containing spectroscopic abundance determinations for 14 elements produced in various nuclear-synthesis processes for 90 open clusters. The catalog also contains the positions, ages, velocities, and elements of the Galactic orbits of the clusters. The relative abundances of both r-elements (Eu) and s-elements (Y, Ba, La, and Ce) in clusters with high, elongated orbits and in field stars of the Galactic thin disk display different dependences on metallicity, age, Galactocentric distance, and the elements of the Galactic orbits, supporting the view that these objects have different natures. In young clusters, not only barium, but also the three other studied s-elements display significantly higher relative abundances than field stars of the same metallicity. The relative abundances of Eu are lower in highmetallicity clusters ([Fe/H] > -0.1) with high, elongated orbits than in field giants, on average, while the [Eu/Fe] ratios in lower-metallicity clusters are the same as those in field stars, on average, although with a large scatter. The metallicity dependence of the [O, Mg/Eu] ratios in clusters with high, elongated orbits and in field stars are substantially different. These and other described properties of the Eu abundances, together with the properties of the abundances of primary a-elements, can be understood in a natural way if clusters with high, elongated orbits with different metallicities formed as a result of interactions of two types of high-velocity clouds with the interstellar medium of the Galactic disk: low-metallicity highvelocity clouds that formed from “primordial” gas, and high-metallicity clouds with intermediate velocities that formed in “Galactic fountains.”     

Chemical abundance analysis for the atmospheres of red giants in the Hercules moving group

The results of a comparative analysis of the kinematics, ages, and elemental abundances for 17 red giants in the Hercules moving group are presented. Model atmospheres are used to determine the parameters of the stellar atmospheres and the abundances of about 20 elements. The masses and ages of the stars are estimated, and the components of their Galactic velocities and the elements of their Galactic orbits are calculated. Our analysis demonstrates that the Hercules stream is a heterogeneous group of objects from the thin and thick disks.     

Abundances of chemical elements in the Earth’s crust

The evaluation of the abundances of chemical elements in the Earth’s crust is a pivotal geochemical problem. Its first solutions in the early 20th century formed the empirical groundwork for geochemistry and justified concepts about the unity of the material of the Universe, the genesis of the chemical elements, and the geochemical differentiation of the Earth. The accumulation of newly obtained data called for the revision of this problem, and a series of papers by A.P. Vinogradov, which were published in Geokhimiya in 1956–1962, presented reevaluated contents of elements in the continental crust. In these papers, A.P. Vinogradov relied on the classic idea of the geochemical balance of the sedimentary process. These generalizations provided the foundation for the quantitative characterization of the geochemical background of the biosphere and allowed Vinogradov to formulate the principles of the melting and degassing of material in the outer Earth’s shells during the geologic history, a concept that became universally acknowledged in modern geochemistry and geology. The composition of the Earth’s crust can also be evaluated based not on the principle of geochemical balance in the sedimentary process but on data on the actual abundances of major magmatic, metamorphic, and sedimentary rock types. The possibility of this solution was provided after the extensive research of A.B. Ronov, who managed to develop a quantitative model for the structure of the Earth’s sedimentary shell. Based on these data, A.B. Ronov, A.A. Yaroshevsky, and A.A. Migdisov published a series of papers in Geokhimiya in 1967–1985 that presented a model for the chemical structure of the Earth’s crust with regard for the material composing not only the upper part of the continental crust but also its deep-seated granulite-basite layer and the oceanic crust. The quantitative estimates thus obtained led the authors to important conclusions: first, it was demonstrated that the estimated abundances of elements in the granite-metamorphic layer of the continental crust presented in the classic works by A.P. Vinogradov are confirmed by independent materials, which are based on data on the actual abundance of rocks. Second, incredible as it was, the principle of geochemical balance in the sedimentary process in application to Ca and carbonates appeared to be invalid. This problem remains unsettled as of yet and awaits its resolution.     

中国花岗岩类化学元素丰度及特征

在全国范围内 750个有代表性的大中花岗岩类岩体上,采集了 6 080件样品,组合成 768件组合样.所有样品完全采用无污染加工方案进行加工和制备.选用了以电感耦合等离子体质谱 (ICP-MS)、仪器中子活化和 X射线荧光光谱为主的多种先进的分析方法对这些花岗岩类样品进行了分析测试,实测元素近 70种.使用国家一级地球化学标准物质和重复测试样品进行质量监控,确保了分析数据的准确性和可靠性.依据这些实测分析数据,计算并提出了中国花岗岩类和不同构造单元、不同时代花岗岩类的近 70种化学元素或成分的丰度,探讨了中国花岗岩类和不同构造单元、不同时代花岗岩类元素丰度的特征.     

A comparative analysis of chemical abundances in the atmospheres of red giants of different age groups

We analyze previously published chemical abundances in the atmospheres of red giants. Excess abundances are observed not only for Na, but also for Al and Si, with the overabundances increasing with the stars’ luminosity. The observed anomalies provide evidence that, in addition to the CNO hydrogen-burning cycle, the Mg-Al and Ne-Na cycles operate in the interiors of main-sequence stars; their products are brought to the stellar atmospheres by convection after the transition to the red-giant phase. The abundance anomalies for s-process elements, also observed in the atmospheres of field stars, testify to the presence of a substantial number of neutrons. The s-process abundance anomalies are absent from giants of the young Hyades cluster.     

The role of metals in cooling gas behind shock fronts in the atmospheres of cool stars

The influence of various chemical elements on radiative cooling of the gas flowing from a viscous jump is investigated in a model with a stationary shock in the atmosphere of a cool star. A closed system of equations is written for the thermal energy per heavy particle, the electron temperature, and the relative concentrations of elements in all ionization states. In addition to hydrogen and helium, atomic, singly ionized, and doubly ionized carbon, nitrogen, oxygen, sodium, magnesium, aluminum, silicon, sulfur, potassium, calcium, and iron are included, assuming they have their normal cosmic abundances. The high optical depth in Lyman-series lines leads to a return of the thermal energy to electrons via secondary collisions. As a result, the contribution of hydrogen to the cooling rate falls to the level of the contribution of metals, mainly carbon, magnesium, and iron. Thus, such shock models are able to explain the presence of bright metal lines in the spectra of cool and solar-type stars.     

Some problems in determining elemental abundances in the atmospheres of giants and dwarfs of the HR 1614 moving cluster

The atmospheric abundances of various chemical elements and other atmospheric parameters of four stars belonging to the HR 1614 moving cluster are determined and analyzed using a single technique. For three of the stars, the derived atmospheric parameters are typical of stars of their types, and their elemental abundances are close to those determined earlier for these and other stars of the moving cluster. However, the atmospheric parameters derived for the red dwarf HD 32147 would be more typical of a giant, and its metallicity is much lower than is characteristic of stars of this moving group.

     

Abundances and sources of rare-earth elements in the modern volcanogenic hydrothermal systems of Kamchatka

Sources of modern hydrothermal systems are considered on the basis of high-precision REE data on representative samples of characteristic hydrochemical types of hydrothermal systems of the Eastern Volcanic Belt of Kamchatka and data available on modern magmatogenic fluid systems of the Kamchatka, Kuriles, and oceanic rift zones. It was found that modern high-temperature chloride-sodium hydrothermal vents have elevated REE contents and that all considered hydrochemical types of the Kamchatka hydrothermal systems are characterized by similar REE patterns. High REE contents in the hydrothermal vents with pH up to 5.0 show bimodal distribution. Correlations established between La/Yb ratios in the hydrothermal vents of various types and in the igneous rocks of the Eastern Volcanic Belt of Kamchatka are interpreted in genetic terms. A positive correlation was found between rare-earth elements, chlorine and boron contents. It was noted that all considered hydrochemical types show distinct negative europium anomaly, whereas submarine hydrothermal vents of oceanic rift zones are characterized by positive europium anomaly. It was proposed that REE was transported in the hydrothermal vents from apical zones of deep-seated magma chambers containing acid derivatives.     

中国不同岩石类型花岗岩类元素丰度及特征

依据采自全国范围内约750个有代表性的大、中型花岗岩类岩体上的768件组合样的实测分析数据,这里计算并提出了碱长花岗岩、正长花岗岩、二长花岗岩、花岗闪长岩、石英二长岩、石英二长闪长岩等中国不同岩石类型的花岗岩类岩石近七十种化学元素或成份的丰度,探讨了中国不同花岗岩类岩石的岩石化学特征和微量元素丰度的特征。     

Abundances of chemical elements of the granitoids in different geotectonic units of China and their characteristics

On the basis of actual analytical data of 767 composited samples collected mainly from about 750 large to middle representative granitoid bodies all over China, the average chemical compositions and element abundances of about 70 chemical elements of SiO₂, Al₂O₃, Fe₂O₃, FeO, MgO, CaO, Na₂O, K₂O, H₂O⁺, CO₂, TFe₂O₃, Ag, As, Au, B, Ba, Be, Bi, Cd, Cl, Co, Cr, Cs, Cu, F, Ga, Ge, Hf, Hg, Li, Mn, Mo, Nb, Ni, P, Pb, Rb, S, Sb, Sc, Se, Sn, Sr, Ta, Th, Ti, Tl, U, V, W, Zn, Zr, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y in alkalifeldspar granite, syenogranite and adamellite in 7 geotectonic units in China such as Tianshan-Xing’an orogenic series, Sino-Korean metaplatform, Kunlun-Qilian-Qinling orogenic series, Yunnan-Tibet orogenic series, Yangtze metaplatform, South China-Youjiang orogenic zone and Himalayan orogenic belt, are calculated and presented in this paper. In addition, the characteristics of petrochemical parameters, trace element contents and rare earth element distributions of different rock types of the granitoids in different geotectonic units are also sufficiently discussed. Translated from Acta Geologica Sinica, 2007, 81(1): 47–59 [译自: 地质学报]     

Analysis of the Na,Mg, Al,and Si abundances in the atmospheres of red giants of different spectral subgroups

We analyze the Na, Mg, Al, and Si abundances in the atmospheres of more than 40 stars, includingred giants of different spectral subgroups (normal red giants, mild and classical barium stars) and several supergiants. All these elements exhibit abundance excesses, with the overabundance increasing with the star’s luminosity. The dependence of the overabundances for each of these elements on the luminosity (or log g) is the same for all the spectral subgroups, testifying to a common origin: they are all products of hydrogen burning in the NeNa and MgAl cycles that have been dredged up from the stellar interiors to the outer atmospheric layers by convection that gradually develops during the star’s evolution from the main sequence to the red-giant stage. The sodium abundances derived for several stars are lower than for other stars with similar atmospheric parameters. The ages and kinematic characteristics of these two groups of stars suggest that they probably belong to different stellar generations.     

Abundances of carbon,nitrogen, oxygen,and other elements in the atmosphere of the giant 30 LMi

We have studied the star 30 LMi using high-dispersion CCD spectra and photographic observations. We estimate the star's effective temperature T_eff=7210 K, gravity log g=3.34, and microturbulence velocity ξ_t=5.8 km/s. The carbon abundance, log ?(C)=8.57, is close to the solar value. Nitrogen (log ?(N)=7.81), oxygen (log ?(O)=8.76), and sulfur (log ?(S)=7.20) are slightly underabundant compared to the Sun, by ?0.16 dex, ?0.11 dex, and ?0.13 dex, respectively. A relatively large underabundance of ?0.27 dex was found for titanium (log ?(Ti)=4.75), whereas zinc shows an over-abundance by +0.21 dex (log ?(Zn)=4.81). Sodium (log ?(Na)=6.26), silicon (log ?(Si)=7.57), calcium (log ?(Ca)=6.38), chromium (log ?(Cr)=5.62), iron (log ?(Fe)=7.51), nickel (log ?(Ni)=6.34), and yttrium (log ?(Y)=2.34) exhibited abundances close to the solar values. We find no chemical anomalies characteristic of Am stars or δ Scuti stars in the spectrum of 30 LMi.     

Abundances of carbon, nitrogen, oxygen, and other elements in the atmosphere of the giant 20 Peg

We have studied the giant 20 Peg using high-resolution spectra. We derive the star’s effective temperature, T _eff=6970 K, gravity, logg=3.35, and microturbulence velocity from FeI lines, ξ_t=2.70 km/s, and from NiI lines, ξ_t=2.45 km/s. The abundances of carbon, log?(C)=8.78, nitrogen, log?(N)=8.28, and silicon, log?(Si)=7.85, are enhanced compared to the solar values by 0.23, 0.31, and 0.30 dex, respectively. The abundances of oxygen, log?(O)=8.83, sodium, log?(Na)=6.37, and sulfur, log?(S)=7.33, are nearly solar. Calcium and nickel show normal abundances, log?(Ca)=6.44 and log?(Ni)=6.32. Iron log?(Fe)=7.63 and yttrium log?(Y)=2.41 are only slightly overabundant compared to the solar values (by 0.13 and 0.17 dex). We find a rather large (0.95 dex) overabundance of barium log?(Ba)=3.08.     

Abundances and modes of occurrence of trace elements in the Çan coals (Miocene), Çanakkale-Turkey

This study presents the concentrations and modes of occurrence of trace elements in 81 coal samples from the Çan basin of northwestern Turkey. The concentration of trace elements in coal were determined by inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry. Additionally, traditional coal parameters were studied by proximate, ultimate, X-ray diffraction, and petrographic analyses. Twenty trace elements, including As, B, Ba, Be, Cd, Cu, Co, F, Hg, Mo, Ni, Pb, Sb, Se Sn, Th, Tl, U, V, and Zn, receive much attention due to their related environmental and human health concerns. The Çan coals investigated in this study are lignite to sub-bituminous coal, with a broad range of ash yields and sulphur contents. The trace element concentrations show variety within the coal seams in the basin, and the affinities vary among locations. The concentrations of B, Ba, Be, Cd, Cu, Co, F, Hg, Mo, Ni, Pb, Sb, Se, Sn, Tl, and Zn in Çan coals are within the Swaine's worldwide concentration range, with the exception of As, Th, U, and V. On the other hand, compared with world coals, the Çan basin coals have higher contents of As, B, Cu, Co, Mo, Pb, Th, U, V, and Zn. Based on statistical analyses, most of the trace elements, except for U, show an affinity to ash yield. Elements including As, Cd, Hg, Se, Cu, Mo, Ni, and Zn, show a possible association with pyrite; however, the elements Se, B, and Mo can be have both organic and inorganic associations.     

Separation of chemical elements in the atmospheres of CP stars under the action of light induced drift

A mechanism for the separation of chemical elements and isotopes in the atmospheres of chemically peculiar (CP) stars due to light-induced drift (LID) of ions is discussed. The efficiency of separation due to LID is proportional to the relative difference of the transport frequencies for collisions of ions of heavy elements located in the excited state (collision frequency ν _e ) and ground state (collision frequency ν _g ) with neutral buffer particles (hydrogen and helium), (ν _e ? ν _g )/ν _g . The known interaction potentials are used to numerically compute the relative difference (ν _e ^H ? ν _g ^H )/νg H for collisions between the ions Be⁺, Mg⁺, Ca⁺, Sr⁺, Cd⁺, Ba⁺, Al⁺, and C⁺ and hydrogen atoms. These computations show that, at the temperatures characteristic of the atmospheres of CP stars, T = 7000?20 000 K, values of |ν _e ^H ?ν _g ^H |/ν _g ^H ≈ 0.1?0.4 are obtained. With such relative differences in the transport collision frequencies, the LID rate of ions in the atmospheres of coolCP stars (T < 10000 K) can reach ~0.1 cm/s,which exceeds the drift rate due to light pressure by an order of magnitude. This means that, under these conditions, the separation of chemical elements under the action of LID of ions could be an order of magnitude more efficient than separation due to light pressure. Roughly the same manifestations of LID and light pressure are also expected in the atmospheres of hotter stars (20 000 > T > 10 000 K). LID of heavy ions is manifest only weakly in very hot stars (T > 20 000 K).