Parameters of UX CVn

We have derived a complete set of parameters for the close binary system UX CVn made up of degenerate objects based on photometric and spectral observations. The total mass of the components is close to one solar mass, so that its further evolution cannot result in a type-I supernova. The spectrum of the binary indicates that the surface temperature of the hot subdwarf may have increased by 2000 K over 40 years. This heating rate is consistent with theoretical estimates for evolutionary tracks of low-luminosity hot subdwarfs. We also determined the abundances for ten elements in the atmosphere of the primary, which are consistent with the hypothesis that the binary is a member of Population II. There are signs of synthesized material ejected onto the surface of the star.     

The evolutionary status of ultraluminous X-ray sources

We analyze models for quasi-stationary, ultraluminous X-ray sources (ULXs) with luminosities 10³⁸–10⁴⁰ erg/s exceeding the Eddington limit for a ～1.4M_⊙ neutron star. With the exception of relatively rare stationary ULXs that are associated with supernova remnants or background quasars, most ULXs are close binary systems containing a massive stellar black hole (BH) that accretes matter donated by a stellar companion. To explain the observed luminosities of ～10⁴⁰ erg/s, the mass of the BH must be ～40M_⊙ if the accreted matter is helium and ～60M_⊙ if the accreted matter has the solar chemical composition. We consider donors in the form of main-sequence stars, red giants, red supergiants, degenerate helium dwarfs, heavy disks that are the remnants of disrupted degenerate dwarfs, helium nondegenerate stars, and Wolf-Rayet stars. The most common ULXs in galaxies with active star formation are BHs with Roche-lobe-filling main-sequence companions with masses ～7M_⊙ or close Wolf-Rayet companions, which support the required mass-exchange rate via their strong stellar winds. The most probable candidate ULXs in old galaxies are BHs surrounded by massive disks and close binaries containing a BH and degenerate helium-dwarf, red-giant, or red-supergiant donor.     

The evolutionary status of the most massive WNh stars in close binary systems. NGC 3603-A1

The evolution of the components of the unique, massive, close binary system NGC 3603-A1, which consists of stars of spectral types WN6ha and WN6h, is analyzed. The component masses are estimated to be 116 and 89M _⊙, close to the highest measured stellar masses. Numerical modeling of the evolution of the components has been carried out, taking into account mass loss via the stellar winds of the two massive stars. It is shown that the maximum possible initial component masses are close to 140 and 125M _⊙. The components are currently slightly evolved main-sequence stars, with a comparative low degree of helium enrichment at their surfaces. Further evolution of the system will lead to filling of the Roche lobe of the primary and subsequent evolution in a common envelope. This may lead to the merger of the components, with the evolution of the system ending in the formation of a singlemassive black hole after the second supernova explosion. Otherwise, depending on the masses of the resulting black holes, either a binary system of two black holes or two unbound black holes may form, accompanied by gamma-ray bursts.     

Lithium lines in the spectra of M dwarfs: UX Tau C

The results of numerical modeling of lithium lines in the spectra of M dwarfs are discussed. The behavior of the lithium lines relative to the local pseudocontinuum formed by molecular bands is analyzed as a function of model atmosphere parameters: effective temperature T _eff, gravity logg, and metallicity μ The molecular opacity was computed using the just overlapping line approximation (JOLA) and “line-by-line” methods. The pseudo-equivalent widths of lithium lines depend appreciably on metallicity μ and weakly on T{nteff}. The lithium abundance in the atmosphere of UX Tau C is redetermined. Previous studies underestimated the lithium abundance in this star as a result of the use of insufficiently accurate molecular-line lists. The new lithium abundance log N (Li)=3.2±0.3was derived by comparing the observed profiles of the 670.8 nm resonance doublet lines with profiles calculated using the new TiO line list of Plez.¹ The new abundance agrees with the atmospheric lithium abundances of the other two components in the stellar system, providing further evidence that the three stars in the UX Tau system have the same age. A comparison of the observed spectra of UX Tau C near the lithium resonance doublet (665–680 nm) with spectra computed using JOLA and line-by-line methods suggests that the list of Plez is the best currently available.     

Unusual Eclipse of the UX Ori Type Star V719 Per

Astronomy Reports - The results of new photometric ( $$VRI$$ ) observations of the young star V719 Per from the IC 348 cluster are presented. Up until 2014, this star demonstrated brightness...     

Atmospheric chemical abundances and the evolutionary status of the spectroscopic and speckle-interferometric binary 9 Cyg

We have performed speckle interferometry with the 6-m telescope of the Special Astrophysical Observatory and spectroscopy (at 3700–9200 Å) with the 2-m telescope at Peak Terskol of the spectroscopic and interferometric binary 9 Cyg, which is a composite-spectrum star with an orbital period of 4.3 yrs. The atmosphere of the system’s primary component is analyzed in detail. The luminosities of both components estimated to be L ₁ = 103.8 L _⊙, L ₂ = 55.2 L _⊙, where L _⊙ is the solar luminosity, and their effective temperatures to be T _e (1) = 5300 K and T _e (2) = 9400 K. The abundances of C, N, O, Fe, and other elements in the primary’s atmosphere have been derived. The chemical composition shows signatures of mixing of material from its atmosphere and the region of nuclear reactions. The evolutionary status of 9 Cyg has been determined. The binary’s age is about 400 million years; the brighter star is already in the transition to becoming a red giant, while the secondary is still in the hydrogen-burning stage near the zero-age main sequence. We suggest an evolutionary model for the binary’s orbit that explains the high eccentricity, e = 0.79.     

Photometric activity of UX orionis stars and related objects in the near infrared and optical: CO Ori,RR Tau,UX Ori,and VV Ser

This paper continues a study of the photometric activity of UX Ori stars in the optical and near-infrared (JHKLM bands) initiated in 2000. For comparison, the list of program stars contains two Herbig Ae stars that are photometrically quiet in the optical: MWC480 andHD179218. Fadings ofUXOri stars in the optical (V band) due to sporadic increases of the circumstellar extinction are also observed in the infrared (IR), but with decreasing amplitude. Two stars, RR Tau and UX Ori, displayed photometric events when V -band fadings were accompanied by an increase in IR fluxes. Among the two Herbig Ae stars that are photometrically quiet in the optical, MWC 480 proved to be fairly active in the IR. Unlike the UX Ori stars, the variation amplitude of MWC 480 increases from the J band to the M band. In the course of the observations, no deep fadings in the IR bands were detected. This indicates that eclipses of the program stars have a local nature, and are due to extinction variations in the innermost regions of the circumstellar disks. The results presented testify to an important role of the alignment of the circumstellar disks relative to the direction towards the observer in determining the observed IR variability of young stars.     

地热回灌的发展现状

地热回灌是一种避免地热废水直接排放引起的热污染和化学污染的措施,并对维持热储压力,保证地热田的开采技术条件具有重要的作用.目前回灌已经成为世界范围内数十个重要的地热田生产运行中的一项日常工作,在美国、新西兰、冰岛、意大利、法国、日本、罗马尼亚、丹麦、菲律宾和萨尔瓦多等十多个国家得到了广泛的应用.在国内,北京、天津的地热回灌也已经有了良好的开端.回灌是地热田管理中最为复杂的一项技术,为了避免因回灌而引起热储冷却,需要进行回灌试验和示踪试验,并在回灌过程进行全面的监测工作.     

Diagnostics for accretion disks around UX Ori stars based on Balmer, Paschen, and Brackett Lines

We have modeled the H_α, H_β, and H_γ (Balmer series), P₁₄ (Paschen series), and Br_γ (Brackett series) hydrogen lines formed in the inner regions of the accretion disk around the Herbig Ae star UX Ori. Our calculations are based on spectra obtained with the Nordic Optical Telescope (NOT) and the IRTF. We computed a grid of non-LTE models for a radiating area in the accretion disk and determined the basic parameters of the lines using the method of Sobolev. Analyzing the theoretical and observed line profiles, equivalent widths, and luminosities, we have estimated the accretion rate and electron-temperature distribution in the inner parts of the accretion disk. The accretion rate of UX Ori is about $\dot M_a = (3 - 10) \times 10^{ - 9} M_ \odot /yr$ , and the temperature distribution is consistent with the power law T(r)=T(r _*)(r/r _*)^?1/n , where the electron temperature near the stellar surface T(r _*) is 15000–20000 K and the power-law index n≈2–3 is about two to three. The resulting value for $\dot M_a $ eliminates problems connected with the application of magnetospheric accretion models to Herbig Ae/Be stars. Another important conclusion is that, at the estimated accretion rate, the energy release is substantially (about two orders of magnitude) lower than the stellar luminosity. Therefore, the optical radiation of UX Ori accretion disks cannot appreciably contribute to the observed variability of these stars, which must be determined mainly by variability in the circumstellar extinction.     

Application of evolutionary algorithms to develop a rule set for assessing the rehabilitation status of asbestos mines in South Africa

Asbestos mining has left a legacy of pollution in former mining areas that continues to negatively affect both the environment and local communities. In 2007, the Rehabilitation Prioritisation Index was developed as a scientific tool to indicate the preferred sequence for mine site rehabilitation and served as a departure point for the present investigation in which a database for the rehabilitation success of asbestos sites was developed. Broad-based quantitative and qualitative data, typically used for monitoring rehabilitation success, including amongst others, soil cover depth, physical and chemical soil properties, microbial activity, vegetation properties and small mammal abundance were analysed using multivariate statistics, specifically a redundancy analysis. The most representative model was subsequently selected for the classification of the rehabilitated sites. The multivariate analysis revealed those factors typically associated with rehabilitation success or failure, as well as essentials to be addressed. The feasibility of development of a rule set for rehabilitated site classification was firstly investigated using neural networks which also assisted in the selection of significant parameters. Results from the neural network approach were then used to guide parameter selection for the evolutionary algorithm software. The coordinate scores for the first two axes of the redundancy analysis served as targets for the evolutionary algorithms. Overall, a targeting match of 71 % for the first axis coordinates and 38 % for the second axis coordinates were obtained. Contributing parameters for the rule set included: Cl, K, pH, percentage organic carbon, Zn, NH₄ and SO₄ content of the sites.     

Modeling of Hydrogen Emission Lines in the Spectrum of UX Ori in Its Bright State and during Eclipses

Astronomy Reports - The hydrogen spectrum of the UX Ori-type star is modeled in a bright state and during an eclipse by an opaque dusty fragment of its own protoplanetary disk. The disk wind is...     

The mass of the black hole in the X-ray binary M33 X-7 and the evolutionary status of M33 X-7 and IC 10 X-1

We have analyzed the observed radial-velocity curve for the X-ray binary M33 X-7 in a Roche model. We have analyzed the dependence between the component masses and the degree of filling of the optical star’s Roche lobe to obtain the ratio of the masses of the optical star and compact object. For the most probable mass of the optical star, m _v = 70 M⊙, the mass of the compact object is m _x = 15.55 ± 3.20 M⊙. It has been shown that black holes with masses of mx = 15 M⊙ and even higher can form in binaries. We present characteristic evolutionary tracks for binary systems passing through an evolutionary stage with properties similar to M33 X-7-type objects. According to population-synthesis analyses, such binaries should be present in galaxies with masses of at least 10¹¹ M⊙. The present number of such systems in M33 should be of the order of unity. We have also studied the evolutionary status of the X-ray binary IC 10 X-1 with a Wolf-Rayet component, which may contain a massive black hole. The final stages of the evolution of the M33 X-7 and IC 10 X-1 systems should be accompanied by the radiation of gravitational waves.     

Structure of the accretion disk in the cataclysmic variable UX UMa in the transition to its quiescent state

Our analysis of BV RI light curves for the cataclysmic variable UX UMa obtained in intermediate activity states, in the transition between the active and quiescent states of the system on March 12, 1997 and May 3, 2000, shows that the shapes of these light curves cannot be adequately described using the standard hot-spot model. A model with a “hot line” near the edge of the disk and a two-armed spiral structure on the disk surface reproduces much better out-of-eclipse variations in the light curves. The presence of an extended hot line can explain the anomalous shape of the I light curve on March 12, 1997. The decrease in the observed luminosity of the system between March 12, 1997 and May 3, 2000 could be due to a decrease in the disk luminosity by a factor of 2–2.5; the higher disk luminosity on the earlier date is associated with appreciable deviations of the radial temperature distribution of the disk material from that for the standard model. The phases and depths of dips in the out-of-eclipse sections of the UX UMa light curves are due primarily to the parameters of the complex shape of the accretion disk, which has a spiral structure located mainly near its outer edge. The contribution of the spiral arms in the V filter reaches 20–50% of the total disk radiation. The crest of the first spiral wave in our model maintains its approximate position in azimuth; this structure could represent a bulge in a halo at the outer edge of the disk near orbital phases φ ～ 0.7, in the direction of the continuation of the extended shock in the disk itself. The position of the crest of the second spiral arm changes with time. This structure may represent a one-armed spiral wave near the apastron of the weakly elliptical disk. Finally, the observations testify to the presence of another spiral arm that is les clearly manifest in terms of both its luminosity and its height above the unperturbed disk surface. Thus, in an intermediate activity state of UX UMa, the surface of the accretion disk is distorted by the action of a two-armed spiral structure in the outer regions of the disk, which is asymmetric in both its luminosity and dimensions, and a bulge at the disk edge in the region of its interaction with the inflow to the disk.     

亚洲中部及邻区成矿元素的演化趋势

亚洲中部及邻区的成矿作用,在地球演化早期即前寒武纪,以碳、硼、磷、镁、金、铁、铜等为主,在晚期即显生宙后期,以铝、铅锌、钨锡、钼、汞锑等为主。前寒武纪碳(C,石墨矿)的集中发育可能与地球早期地壳和大气圈中氧丰度不高有关,碳不易氧化;硼(B)、磷(P)说明在地球演化早期,地壳中相对富含挥发分元素;镁(Mg)、铁(Fe)、金(Au)说明在地球演化早期,地壳中镁铁质成分占据主导地位。铜(Cu)系多期成矿的元素,其成矿作用主要发生在元古宙、古生代和中生代。在经济上有意义的铝(Al)即铝土矿的成矿高峰期,以中国为例,主要出现在石炭—二叠纪。铅(Pb)、锌(Zn)、钨(W)、锡(Sn)、钼(Mo)主要成矿于中生代。汞(Hg)、锑(Sb)初步沉积在古生代,但成矿则主要在中生代,一般说来,比铅、锌、钨、锡、钼更晚。这些元素在周期表中的位置,C、B、P、Mg、Al属第2～3周期,其成矿主要出现在地球演化早期;Fe、Au、Cu、Pb、Zn、W、Sn、Mo、Hg、Sb属第4～6周期,其成矿主要出现在地球演化晚期。铀(U)为第7周期,成矿更晚;中国铀矿的成矿主要在钨(W)、锡(Sn)、钼(Mo)、铋(Bi)、铁(Fe)、铜(Cu)、锌(Zn)、铌(Nb)、钽(Ta)、稀土(REE)等所有矿化之后。换言之,在地球的演化历史中,成矿元素的原子结构由简单逐渐趋于复杂,其外层电子层数由2～3层(C,B,P等)发展到多达7层(U)。由此可见,在普查找矿中,寻找周期表前部的元素的矿床,应当主要在古老地壳地区(前寒武纪地层发育地区)进行;寻找周期表中部的元素的矿床,在古老地壳地区和年青地壳地区都应注意;而寻找周期表后部的元素的矿床,则主要应在年青地壳发育地区,即年青的地质、构造、岩浆及热液活动发育的地区进行。显生宙以来,特别是晚古生代和中生代以来,地球上水圈、大气圈和生物圈的进一步发育,使成矿元素的演化趋势进一步复杂化;这一阶段外生矿床主要是沉积矿床的形成,以及特别是碳、氢和氧的再循环,导致了大量煤、石油和天然气的生成。     

Atmospheric lithium abundances of the carbon giants AQ And,HK Lyr,UX Dra,and WZ Cas

The LTE lithium abundances, logN (Li), have been determined for the atmospheres of the four carbon giants AQ And, HK Lyr, UX Dra, and WZ Cas, applying the synthetic-spectrum technique to the LiI λ670.8 nm resonance doublet. We used estimates of the effective temperatures T _eff, metallicities, elemental abundances, and carbon-isotope ratios for these stars from the literature [12C/13C]. The resulting lithium abundances depend significantly on the adopted T _eff, so that we can find each star’s range of possible logN(Li) values for a given range of effective temperatures (ΔT _eff = 200−300 K). The uncertainty in the derived logN(Li) values is 1.3 for AQ And and UX Dra, 0.5 for HK Lyr, and 0.8 for WZ Cas. Our most probable logN(Li) values (or ranges) are −1.25 for AQ And, −1.2 for HK Lyr, −1.0 ≤ logN(Li) ≤ +0.3 for UX Dra, and 4.3 ≤ logN(Li) ≤ 4.8 for WZ Cas. The derived C/O ratios for the stellar atmospheres also depend on T _eff. Possible uncertainties in other atmospheric parameters do not change logN(Li) by more than 0.2.     

The status and prospects of risk assessment

After discussing the changing nature of perceived risk problems, the status of risk assessment is described in relation to its origins and in particular to its roots in the environmental impact statement process. The nature of risk, its component elements and the manner in which existing concepts of risk have been reflected in risk assessment methods are described. The paper considers two emerging schools of thought in current risk assessment studies: one that calls for more accurate measures of risk and increasingly comprehensive event prediction models to determine risk acceptability and another which argues that the acceptance of risk is less dependent on the accuracy of risk analyses than it is on the nature of the decision-making process and in particular on whether compensation is provided for those bearing a disproportionate share of risk.     

The ethno-demographic status of the Baltic States

The essay examines historic and current ethnodemographic trends in spatial and cultural contexts in the Baltic States. Fifty years of Soviet rule, with deliberate policies to dilute the relative homogeneity of the Balts through ethnocide, in-migration, and political dominance by Moscow, has left tensions between citizens of the Baltic States and illegal immigrants, mostly Russians. Estonians, and Latvians, in particular, fear ethnic and cultural extinction. The process of ethnic dilution and mixing under the Soviets is examined in terms of rural-urban contexts, the workplace, employment, housing, and education. Europe's smallest ethnic group, the Livs of Latvia, is also examined. Current demographic trends are analysed and prospects for ethnic harmony in these multi-ethnic societies are interpreted. A recurrent theme is that Latvia, with 52% of the population Latvian, is facing the most difficulties; Lithuania, with 80% Lithuanians, the least.     

The Northern Carpathians plate tectonic evolutionary stages and origin of olistoliths and olistostromes

The olistostromes formed in Northern Carpathians during the different stages of the development of flysch basins, from rift trough post-rift, orogenic to postorogenic stage. They are known from the Cretaceous, Paleocene, Eocene, Oligocene and Early Miocene flysch deposits of main tectonic units. Those units are the Skole, Subsilesian, Silesian, Dukla and Magura nappes as well as the Pieniny Klippen Belt suture zone. The oldest olistoliths in the Northern Carpathians represent the Late Jurassic-Early Cretaceous rifting and post-rifting stage of the Northern Carpathians and origin of the proto-Silesian basin. They are known from the Upper Jurassic as well as Upper Jurassic-Lower Cretaceous formations. In the southern part of the Polish Northern Carpathians as well as in the adjacent part of Slovakia, the olistoliths are known in the Cretaceous- Paleocene flysch deposits of the Pieniny Klippen Belt Zlatne Unit and in Magura Nappe marking the second stage of the plate tectonic evolution - an early stage of the development of the accretionary prism. The most spectacular olistostromes have been found in the vicinity of Haligovce village in the Pieniny Klippen Belt and in Jaworki village in the border zone between the Magura Nappe and the Pieniny Klippen Belt. Olistoliths that originated during the second stage of the plate tectonic evolution occur also in the northern part of the Polish Carpathians, in the various Upper Cretaceous-Early Miocene flysch deposits within the Magura, Fore-Magura, Dukla, Silesian and Subsilesian nappes. The Fore-Magura and Silesian ridges were destroyed totally and are only interpreted from olistoliths and exotic pebbles in the Outer Carpathian flysch. Their destruction is related to the advance of the accretionary prism. This prism has obliquely overridden the ridges leading to the origin of the Menilite-Krosno basin.

In the final, postcollisional stage of the Northern Carpathian plate tectonic development, some olistoliths were deposited within the late Early Miocene molasse. These are known mainly from the subsurface sequences reached by numerous bore-holes in the western part of the Polish Carpathians as well as from outcrops in Poland and the Czech Republic.

The largest olistoliths (kilometers in size bodies of shallow-water rocks of Late Jurassic-Early Cretaceous age) are known from the Moravia region. The largest olistoliths in Poland were found in the vicinity of Andrychów and are known as Andrychów Klippen. The olistostromes bear witness to the processes of the destruction of the Northern Carpathian ridges. The ridge basement rocks, their Mesozoic platform cover, Paleogene deposits of the slope as well as older Cretaceous flysch deposits partly folded and thrust within the prism slid northward toward the basin, forming the olistostromes.     

小波分析的应用现状及展望

小波分析具有多分辨分析的特点,在时频两域都具有表征信号局部特征的能力,是一种窗口大小固定不变,但其形状可以改变的时频局部化分析方法。本文从介绍小波分析的发展简史开始,简述小波分析的基本原理,分析和总结小波分析在地球物理勘探、信号和图像处理中的最新应用成果。讨论小波分析目前应用中存在的主要问题,并展望小波分析一些有前景的应用领域。     

郯庐断裂带北段构造特征及构造演化序列

根据大量野外地质调查和盆地地震资料分析,认为郯庐断裂北段在中-新生代发生多期不同性质的活动,形成各具特色的构造变形现象。密山县知一镇敦密断裂韧性剪切带具有左旋走滑特征,其中黑云母~(40)Ar/~(36)Ar-~(39)Ar/~(36)Ar等时线年龄为161±3Ma,是郯庐断裂带被利用发生第二期左旋走滑运动并向北扩展到中国东北-俄罗斯远东地区的产物。四平市叶赫乡佳伊断裂带中负花状断裂形成于早白垩世早中期,是郯庐断裂北段在早白垩世遭受左旋走滑-拉张作用的典型代表。四平市石岭镇佳伊断裂大型走滑-逆冲断褶带、桦甸县敦密断裂"逆地堑"、沈阳-哈尔滨逆冲断裂形成于晚白垩世嫩江运动-晚白垩世末期,这一时期脆性右旋走滑-逆冲事件规模大,影响范围广,导致整个郯庐断裂北段遭受到强烈改造。佳伊断裂带和敦密断裂带中古近纪盆地在横剖面上呈不对称地堑,并且不对称地堑沿断裂带走向发生断、超方向左右变位,是郯庐断裂带北段在古近纪时受右旋走滑、伸展双重机制控制的产物。根据郯庐断裂带北段中-新生代不同地质时期变形特征,建立了郯庐断裂北段构造演化序列。即郯庐断裂北段构造演化分为左旋韧性剪切(J_2末期)、左旋张扭(K_1早中期)、右旋压扭(K_2晚期-末期)、右旋走滑断陷(E)和构造反转(E_3末期)五个阶段。其演化历史主要受控于环太平洋构造域的构造作用。