Spectroscopic monitoring of V1357 Cyg = Cyg X-1 in 2002–2004

We discuss the results of optical spectroscopic monitoring of Cyg X-1 = HDE 226868/V1357 Cyg in 2002–2004. Our spectroscopy was carried out at the Terskol Observatory (Kabarda-Balkaria, Russia; the resolving power was R = 45 000 and 13 000) and at the Bohyunsan Optical Astronomy Observatory (BOAO, Korea, R = 30 000 and 44 000). Each spectrum covers most of the optical range. We obtained a total of 75 echelle spectra on 33 nights, during both “soft” and “hard” X-ray states of Cyg X-1. We study the influence of the X-rays on spectral-line profiles using RXTE/ASM X-ray data. We find that the X-ray flare of June 13, 2003 resulted in strong variations of the emission profiles of the H_α and Hellλ4686 Å lines within a night. This behavior is due to variations of the ionization state of the gas in the system. We also analyzed line-profile variations with orbital phase. A spectral atlas of Cyg X-1 was created, and the lines it contains identified. A total of 172 stellar lines and blends belonging to 12 chemical elements (H, He, C, N, O, Ne, Mg, Al, Si, S, Fe, Zn) were identified. The spectral classification of HDE 226868 as an ON star is confirmed.     

Parameters of V404 Cyg—A black-hole binary

We present the results of spectroscopic observations of the X-ray binary V404 Cyg obtained on the 6-m telescope of the Special Astrophysical Observatory in 2001–2002. We have used a statistical approach to interpret the radial-velocity curve of V404 Cyg. We derived the dependence of the mass of the X-ray emitting component m_x on the mass of the optical component m_v via an analysis of the radial-velocity curve based on profiles of the CaI 6439.075 Å absorption line synthesized in a Roche model. Using the orbital inclination estimated from the ellipticity of the optical component, i=54°–64°, and the component-mass ratio q=m_x/m_v=16.7 found from the rotational broadening of the spectral lines, we obtain m _s =10.65±1.95M_⊙ for the mass of the black hole.     

A study of the evolution of the close binaries Cyg X-3, IC 10 X-1, NGC 300 X-1, SS 433, and M33 X-7 using the “scenario machine”

Evolutionary tracks for the X-ray binaries Cyg X-3, IC 10 X-1, NGC 300 X-1, SS 433, and M33 X-7 are computed using the Scenario Machine code. The compact objects in IC 10 X-1, NGC 300 X-1, and M33 X-7 are the most massive stellar-mass black-hole candidates. Cyg X-3, IC 10 X-1, and NGC 300 X-1 are the only currently known Wolf-Rayet stars with degenerate companions. SS 433 is the only known superaccretor in the Milky Way. Therefore, the stars studied provide excellent laboratories for testing scenarios for the evolution of binaries under extreme conditions. The classical evolutionary scenario is consistent with modern observational data. During the evolution of these binaries, hypernova explosions accompanied by the collapse of stellar cores with large angular momenta can occur, leading to long gamma-ray bursts. At the end of their evolution, Cyg X-3, IC 10 X-1, NGC 300 X-1, and SS 433 may form binary relativistic objects, which will subsequently merge due to the radiation of gravitational waves. The gravitational waves emitted during mergers of relativistic stars should be detectable by existing and future gravitational-wave antennas. In the course of its future evolution, M33 X-7 will pass through a Thorne-?ytkow stage. The formation of a Thorne-?ytkow object can also be accompanied by gravitational-wave radiation.     

<Emphasis Type="Italic">WBVR</Emphasis> observations of the X-ray star V1341 Cyg = Cyg X-2 in 1986–1992

We present the results of WBVR observations of the low-mass X-ray binary V1341 Cyg = Cyg X-2. Our observations include a total of 2375 individual measurements in four bands on 478 nights in 1986–1992. We tied the comparison and check stars used for the binary to the WBVR catalog using their JHK magnitudes. The uncertainty of this procedure was 3% in the B and V bands and 8%–10% for the W and R bands. In quiescence, the amplitude of the periodic component in the binary’s B brightness variations is within 0.265 ^m –0.278 ^m (0.290 ^m –0.320 ^m in W); this is due to the ellipsoidal shape of the optical component, which is distorted with gravitational forces from the X-ray component. Some of the system’s active states (long flares) may be due to instabilities in the accretion disk, and possibly to instabilities of gas flows and other accretion structures. The binary possesses a low-luminosity accretion disk. The light curves reveal no indications of an eclipse near the phases of the upper and lower conjunctions in quiescence or in active states during the observed intervals. We conclude that the optical star in the close binary V1341 Cyg = Cyg X-2 is a red giant rather than a blue straggler. We studied the longterm variability of the binary during the seven years covered by our observations. The optical observations presented in this study are compared to X-ray data from the Ginga observatory for the same time intervals.     

Analysis of 3D Doppler Tomography of the X-ray Binary System Cygnus X-1 from Spectral Observations in 2007 in the HeII λ 4686 Å Line

This is the second paper in a series dedicated to studies of the X-ray binary Cyg X-1 in the HeII λ 4686 Å line using 3D Doppler tomography. A detailed analysis of the tomogram constructed has made it possible for the first time to obtain information about the motions of gaseous flows including all three velocity components. The observations were obtained in June 2007 at the Terskol Branch of the Institute of Astronomy (Russia) and the National Astronomical Observatory of Mexico. The correctness of the tomographic results and their discussion is analyzed. The results are compared with a 2D Doppler tomogram reconstruction. Model-atmosphere computations of HeII λ 4686 Å line profiles are used to estimate the influence of absorption features of the Osupergiant on the emission structure in the tomogram. The correctness of the 3D solutions is confirmed by the good agreement between the original sequence of spectral data and a control data set computed using the constructed 3D Doppler tomogram. Tomograms constructed using the data of each of the two observatories are compared. The results of the reconstruction for inclinations of the system of 40° and 45° essentially coincide. The maximum absorption (corresponding to the O supergiant) and emission structural features in the 3D tomogram are located in its central (V _x , V _y ) section, where the velocity component perpendicular to the orbital plane V _z is zero. The emission is generated mainly in the outer part of the accretion structure, close to the supergiant. A gaseous stream from the Lagrangian point L1 with its motion close to the orbital plane can be distinguished. Its maximum velocity reaches 800 km/s. The identification of an emission structure with V _z ~ 300 km/s and with V _x , V _y in the velocity interval corresponding to the donor star was unexpected. Its presence may indicate, for example, an outflow of matter from a magnetic pole of the supergiant.     

<Emphasis Type="Italic">UBVJHKLM</Emphasis> photometry of the symbiotic Mira V407 Cyg in 1998–2002

New results of UBV JHKLM photometry of the symbiotic Mira V407 Cyg performed in 1998–2002 are reported. In 2002, these observations were supplemented with RI observations and a search for rapid variability in the V band. The hot component of V407 Cyg experienced a strong flare in 1998, which was the second in the history of photometric observations of this star; this flare is still continuing. During the flare, the spectral energy distribution of the hot component can be approximated by blackbody radiation with a temperature of ～7200 K. At the maximum brightness, the bolometric flux from the hot component did not exceed 3% of the Mira's mean bolometric flux, while its bolometric luminosity was ～400L_⊙. Appreciable variations of the star's BV brightness \((\tilde0\mathop m\limits_. 7)\) on a timescale of several days have been observed. These variations are not correlated with variations of B-V. Flickering on a timescale of several minutes with an amplitude of \(\tilde0\mathop m\limits_. 2\) has been detected in the V band. The observations suggest that the hot component can be in three qualitatively different states. In a model with a rapidly rotating white dwarf, these states can be associated with (i) the quiescent state of the white dwarf (with a very low accretion rate), (ii) an ejection state, and (iii) an accretion state. The Mira pulsation period P is \( \approx 762\mathop d\limits_. 9\), with its infrared maximum occurring ～0.15P after the visual maximum. A “step” is observed on the ascending branch of the Mira infrared light curves. In 1998, the gradual increase of the mean K brightness of the Mira that had been observed since 1984 was interrupted by an unusually deep minimum, after which the mean level of the K brightness considerably decreased.     

The binary systems IC 10 X-1 and NGC 300 X-1: Accretion of matter from an intense Wolf–Rayet stellar wind onto a black hole

The current evolutionary stage of the binary systems IC 10 X-1 and NGC 300 X-1, which contain a massive black hole and a Wolf–Rayet star with a strong stellar wind that does not fill its Roche lobe, is considered. The high X-ray luminosity and X-ray properties testify to the presence of accretion disks in these systems. The consistency of the conditions for the existence of such a disk and the possibility of reproducing the observed X-ray luminosity in the framework of the Bondi–Hoyle–Littleton theory for a spherically symmetric stellar wind is analyzed. A brief review of information about the mass-loss rates of Wolf–Rayet stars and the speeds of their stellar winds is given. The evolution of these systems at the current stage is computed. Estimates made using the derived parameters show that it is not possible to achieve consistency, since the conditions for the existence of an accretion disk require that the speed of the Wolf–Rayetwind be appreciably lower than is required to reproduce the observedX-ray luminosity. Several explanations of this situation are possible: (1) the real pattern of the motion of the stellar-wind material in the binary is substantially more complex than is assumed in the Bondi–Hoyle–Littleton theory, changing the conditions for the formation of an accretion disk and influencing the accretion rate onto the black hole; (2) some of the accreting material leaves the accretor due to X-ray heating; (3) the accretion efficiency in these systems is nearly an order of magnitude lower than in the case of accretion through a thin disk onto a non-rotating black hole; (4) the intensity of the Wolf–Rayet wind is one to two orders of magnitude lower than has been suggested by modern studies.     

The Seyfert 1 galaxy Ark 120 in 1996–2005. Temporal characteristics of the optical variability

We study the optical variability of the Seyfert galaxy Ark 120 using the autocorrelation and structure functions, as well as a periodogram analysis, based on our 1996–2005 U BV RI observations. The autocorrelation function indicates an increase in the correlation to 70% for time shifts of about 430 days. The structure function displays a decrease for these same time shifts, which is interpreted as evidence for periodic events on these timescales. The structure function indicates an increase in the variability amplitude with increasing duration of the variable process. On large time scales, the structure function can be presented as a power-law function with index 0.8–0.9, possibly indicating the presence of unstable processes in the accretion disk. Our search for periodicity in the light curves has revealed a possible period P = 430 days, which has been observed during 13 cycles, as follows from an analysis using continuum from spectral data obtained from 1988 to 2005.     

Data Analysis of Chang’E-1 Gamma-Ray Spectrometer and Global Distribution of U, K, and Th Elemental Abundances

Gamma-ray spectrometer (GRS) is one of the main payloads on the Chang’E-1 (CE-1) lunar probe, mainly aimed to detect the elemental abundances and distributions on the lunar surface. At 03:58 on 28 November 2007, it performed the first observation of the lunar gamma rays. As of 24 October 2008, 2105?h of effective gamma rays spectra had been acquired by CE-1 GRS, which covers the whole surface of the moon. This paper mainly describes the data processing procedures and methods of deriving the elemental abundances by using the CE-1 GRS time series corrected spectra: first, to bin data into pixels for mapping; then, to perform a background deduction of the cumulative spectra and obtain a peak area of the elements; and finally, to use the elemental abundances inversion model to produce the elemental abundances. Based on these processing methods, the global abundance maps of U, K, and Th at a 5°×5° equal-area pixel are acquired by CE-1 GRS data. The paper gives a preliminary analysis of the uncertainties of the elemental abundances     

Influence of cation distribution on the optical absorption spectra of Fe3+-bearing spinel s.s.–hercynite crystals: evidence for electron transitions in VIFe2+–VIFe3+ clusters

Flux-grown Fe³⁺-bearing spinel s.s.–hercynite solid-solution crystals, (Mg _1-y Fe²⁺ _y )Al₂O₄ (0 < y≤ 1), have been investigated by means of electron microprobe technique and Mössbauer and electronic spectroscopy. Obtained results show that different electronic processes cause intense optical absorption bands in the near-infrared spectral region. In addition to an electronic d–d transition in single-ion ^IVFe²⁺, observed at 5200 cm^?1, intense and broad bands at 9500 and 14 500 cm^?1 are assigned to exchange-coupled pair (ECP) and intervalence charge-transfer (IVCT) transitions in ^VI Fe ^{2+ VI} Fe³⁺clusters, respectively. The net linear extinction coefficients of these bands (α) were calibrated against Fe²⁺ and Fe³⁺ concentrations and site distributions previously defined by combined microchemical, Mössbauer, and XRD structural refinement data. The following expressions were obtained: where α is measured in cm^?1 and concentrations are expressed in mol?l^?1. The present results show that optical absorption spectroscopy may be used as a probe to obtain high spatial resolution (?～ 10 μm) information on Fe²⁺ ordering as well as on Fe³⁺ concentrations in minerals belonging to the spinel group.     

Feasibility Analysis of the Use of Binary Genetic Algorithms as Importance Samplers Application to a 1-D DC Resistivity Inverse Problem

DC resistivity inverse problems are ill-posed. For the Vertical Electrical Sounding method the acceptable solutions lie in very narrow elongated-shape regions in the model space. To characterize this ensemble of solutions is a central question. In a Bayesian framework this issue is solved adopting as solution the so-called model posterior probability distribution. However, due to the nonlinearity of the problem, this distribution is not explicitly known, or it is difficult to calculate. Therefore, algorithms that efficiently sample the model space according to it (importance sampling) are very desirable. The main goal of this paper is to numerically explore the performance of binary genetic algorithms as posterior importance sampling strategies. Their behavior will be firstly analyzed using 2D synthetic posterior test functions bearing the relevant properties of the real geo-electrical inverse problem. The conclusions will be again checked through the histogram reconstruction of parameters in a synthetic VES case, and eventually, in a real, higher dimensional, sea-water coastal intrusion problem, by comparing the results with those obtained with a theoretically correct Metropolis-Hasting importance sampler (simulated annealing without cooling). Percentile curves are introduced as an effective tool for risk assessment. We show that binary genetic algorithms perform well under very general assumptions. When the roulette wheel is the selection method used, mutation is over 10%, and the algorithm does not incorporate elitism. The results do not depend on the values of the remaining tuning parameters. Finally, to improve the efficiency of the sampling strategy, we introduce a binary genetic algorithm with oriented search space. This is done with the help of linearization of the forward operator and singular value decomposition around the maximum posterior estimate. It is shown, also, that the logarithmic model parameterization is adequate for this task.     

Analysis of human risks due to dam-break floods—part 1: a new model based on Bayesian networks

Dam breaks have catastrophic consequences for human lives. This paper presents a new human risk analysis model (HURAM) using Bayesian networks for estimating human risks due to dam-break floods. A Bayesian network is constructed according to a logic structure of loss-of-life mechanisms. The nodes (parameters) and the arcs (inter-relationships) of the network are quantified with historical data, existing models and physical analyses. A dataset of 343 dam-failure cases with records of fatality is compiled for this purpose. Comparison between two existing models and the new model is made to test the new model. Finally, sensitivity analysis is conducted to identify the important parameters that lead to loss of life. The new model is able to take into account a large number of important parameters and their inter-relationships in a systematic structure; include the uncertainties of these parameters and their inter-relationships; incorporate information derived from physical analysis, empirical models and historical data; and update the predictions when information in specific cases is available. The application of this model to the study of human risks in a specific dam-break case is presented in a companion paper.     

3D Doppler Tomography of the X-Ray Binary System Cygnus X-1 from Spectral Observations in 2007 in the HeII λ 4686 Å Line

The results of a 3D Doppler tomography analysis for the X-ray binary system Cyg X-1 in the HeII λ 4686 Å line are presented. Information about the motions of gaseous flows outside the orbital plane has been obtained for the first time. Line profiles obtained in June 2007 on the 2-m telescope of the Terskol Branch of the Institute of Astronomy (Russia) and on the 2.1-m telescope of the National Astronomical Observatory of Mexico were used. A detailed analysis of these spectral data is presented: the distribution of the data in time, distribution of orbital phases for the projections, comparison of the line profile shapes for the data from two observatories. The geometry of the total transfer function obtained in the reconstruction is considered. The possibility of applying the profiles obtained to realize 3D tomography is justified. The resolution of the constructed 3D tomogram in velocity space is 60 × 60 × 40 km/s for V _x , V _y , V _z . Fifteen cross sections for 15 different V _z values perpendicular to the orbital plane are presented. The intensity distributions corresponding to the velocities of gaseous structures in the binary system are obtained. The reconstruction was realized using the radio-astronomical approach, developed for solving problems in tomography with a limited number of projections.     

Multicolor photoelectric WBVR observations of the close binary system HZ Her = Her X-1 in 1986–1988. Method and observations

We present results of four-color (WBVR) photoelectric observations of the close binary HZ Her = Her X-1 in 1986–1988. As a rule, the duration of the observations exceeded two 35-day X-ray orbital periods in the 1986–1988 observing seasons. The accuracy and length of the photoelectric observations facilitated multi-faceted studies, which enabled us to define several fine photometric effects in the light curves of the binary more precisely and attempt to interpret them in a model for the matter flow from the optical component to the accretion disk around the neutron star. This model provides a satisfactory explanation for the inhomogeneity of the gas flow and “hot spot,” as well as the existence of distinct “splashes” moving in their own Keplerian orbits around the outer parts of the Keplerian disk. We present series of light curves for all the observing seasons, as well as color-color diagrams that reflect the physics of various photometric effects. The transformation coefficients for each of the instrumental systems for the three observatories at which the observations were carried out are given. Atmospheric extinction was taken into account duringmulti-color observations of the object, with subsequent correction for atmospheric effects with accuracies ranging from 0.003 ^m to 0.005 ^m for air masses up to M(z) = 2.     

Conditions of the Formation of Unique Mineralization with Yushkinite V1 – xS · n[(Mg,Al)(OH)2] in Quartz–Calcite Veins,Pai-Khoi Ridge: Evidence from Study of Fluid Inclusions

Doklady Earth Sciences - The results of the study of fluid inclusions in quartz from quartz–calcite veins with unique yushkinite mineralization are reported. For the first time, it was proved...