Photometric Evolution of the Orbital Light Curves of the Slow Nova V723 Cas     

Sergei Yu. Shugarov  Vitalij P. Goranskij  Nataly A. Katysheva  Anatolij V. Kusakin  Nataly V. Metlova  Igor M. Volkov  DrahomÍr Chochol  Theodor Pribulla  Eugenia A. Karitskaja  Alon Retter  Ohad Shemmer  Yiftah Lipkin 《Astrophysics and Space Science》2005,296(1-4):431-434

UBVRI photoelectric and CCD photometry of the slow nova V723 Cas obtained in the years 1995–2003 is presented. The evolution of light curves in 1-year intervals, folded with the orbital period 0.69326 days, shows an increase of the amplitude of the wave-like variations from 0.07 to 1.3 mag during the years 1997–2003. The fact that the shape and amplitude of the orbital light curves does not depend on wavelength is most probably related to the geometry of eclipses combined with the distribution of circumstellar matter in the system.  相似文献   

Measuring the geometry and topology of large-scale structure using SURFGEN: methodology and preliminary results     

Jatush V. Sheth  Varun Sahni  Sergei F. Shandarin  B. S. Sathyaprakash 《Monthly notices of the Royal Astronomical Society》2003,343(1):22-46

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X-rays from cusps of compact remnants near galactic centres     

Sergei Nayakshin  Rashid Sunyaev 《Monthly notices of the Royal Astronomical Society》2007,377(4):1647-1651

Compact remnants – stellar mass black holes and neutron stars formed in the inner few parsec of galactic centres are predicted to sink into the central parsec due to dynamical friction on low-mass stars, forming a high concentration cusp. Same physical region may also contain very high-density molecular clouds and accretion discs that are needed to fuel supermassive black hole (SMBH) activity. Here we estimate gas capture rates on to the cusp of stellar remnants, and the resulting X-ray luminosity, as a function of the accretion disc mass. At low disc masses, most compact objects are too dim to be observable, whereas in the high disc case most of them are accreting at their Eddington rates. We find that for low accretion disc masses, compact remnant cusps may be more luminous than the central SMBHs. This 'diffuse' emission may be of importance for local moderately bright active galactic nuclei (AGNs), especially low-luminosity AGNs. We also briefly discuss how this expected emission can be used to put constraints on the black hole cusp near our Galactic Centre.  相似文献   

Geomorphology of subglacial volcanoes in the Azas Plateau, the Tuva Republic, Russia     

Goro Komatsu  Sergei G. Arzhannikov  Anastasia V. Arzhannikova  Kirill Ershov 《Geomorphology》2007,88(3-4):312-328

The Azas Plateau volcanic field is located in the Tuva Republic of the Russian Federation. The compositions of the Azas Plateau volcanics include low-viscosity trachybasalt and basanite. Volcanic edifices of Middle-Late Pleistocene age are widely distributed in the southeastern part of the volcanic field. There are subglacial volcanoes among the volcanic edifices, and their formation coincided with extensive ancient glaciations in the region. The dominant subglacial volcanoes in the area are tuyas. The general shapes of the tuyas (flat-tops with steep sides) are due to eruptions into meltwater lakes and confinement of ice walls, and effusive subaerial eruptions of basaltic lavas. There are also non-flat-topped subglacial volcanoes and at least one subaerial volcanic edifice in the area. Degradation appears to have modified the primary shapes of the tuya edifices, and such processes seem to include failures of over-steepened slopes, gully formation due to stream runoff and debris flows, cirque/valley glaciation, and modification by rock glaciers. The estimated thicknesses of the ice sheets covering the subglacial volcanoes during their eruptions range 300–600 m on average.  相似文献   

Local Solutions to Inverse Problems in Geodesy     

Frank Bauer  Peter Mathé  Sergei Pereverzev 《Journal of Geodesy》2007,81(1):39-51

In many geoscientific applications, one needs to recover the quantities of interest from indirect observations blurred by colored noise. Such quantities often correspond to the values of bounded linear functionals acting on the solution of some observation equation. For example, various quantities are derived from harmonic coefficients of the Earth’s gravity potential. Each such coefficient is the value of the corresponding linear functional. The goal of this paper is to discuss new means to use information about the noise covariance structure, which allows order-optimal estimation of the functionals of interest and does not involve a covariance operator directly in the estimation process. It is done on the basis of a balancing principle for the choice of the regularization parameter, which is new in geoscientific applications. A number of tests demonstrate its applicability. In particular, we could find appropriate regularization parameters by knowing a small part of the gravitational field on the Earth’s surface with high precision and reconstructing the rest globally by downward continuation from satellite data.  相似文献   

Experimental estimate of a relation between sea wave energies and the Earth’s crust microdeformations     

Grigory I. Dolgikh  Stanislav G. Dolgikh  Sergei N. Kovalev  Vladimir V. Ovcharenko  Vladimir A. Chupin  Vyacheslav A. Shvets  Sergei V. Yakovenko 《Acta Geophysica》2007,55(4):607-618

The experimental data in the microseismic frequency range obtained using the seismo-acoustic-hydrophysical measurement complex are analyzed. The emphasis is put on estimating the ratio between the energy of surface sea wind waves in the area of the Japan Sea where the complex was located and the Earth’s crust microdeformations in this frequency range. The experimental evaluate obtained allow us to estimate the energy re-distribution at the hydrosphere-lithosphere boundary.  相似文献   

Numerical Fourier Expansions of the Planetary Disturbing Function     

Sergei A. Klioner 《Celestial Mechanics and Dynamical Astronomy》2000,77(3):215-238

Various Fourier expansions of the planetary disturbing function can be computed numerically with the use of numerical Fourier analysis. The task to compute the most general five-dimensional Fourier expansion of disturbing function has become feasible with typical server-class computers quite recently. In such an expansion two anomalies, two arguments of perihelions and two longitudes of the node are independent angular variables, while two semi-major axes, two eccentricities and two inclinations are fixed numerically. The semianalytical expansion of the disturbing function resulting from numerical Fourier analysis theoretically converges for any values of the parameters except for those sets of parameters which allow the bodies to collide. Various aspects of the numerical computation of the Fourier expansion are discussed. Theoretical and practical convergence of the Fourier series is discussed and illustrated. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Atmospheric teleconnection patterns and severity of winters in the Laurentian Great Lakes basin     

Sergei Rodionov  Raymond Assel 《大气与海洋》2013,51(4):601-635

Abstract

We analyzed the relationship between an index of Great Lakes winter severity (winters 1950–1998) and atmospheric circulation characteristics. Classification and Regression Tree analysis methods allowed us to develop a simple characterization of warm, normal and cold winters in terms of teleconnection indices and their combinations. Results are presented in the form of decision trees. The single most important classifier for warm winters was the Polar/Eurasian index (POL). A majority of warm winters (12 out of 15) occurred when this index was substantially positive (POL > 0.23). There were no cold winters when this condition was in place. Warm winters are associated with a positive phase of the Western Pacific pattern and El Niño events in the equatorial Pacific. The association between cold winters and La Niña events was much weaker. Thus, the effect of the El Niño/Southern Oscillation (ENSO) on severity of winters in the Great Lakes basin is not symmetric. The structure of the relationship between the index of winter severity and teleconnection indices is more complex for cold winters than for warm winters. It takes two or more indices to successfully classify cold winters. In general, warm winters are characterized by a predominantly zonal type of atmospheric circulation over the Northern Hemisphere (type W1). Within this type of circulation it is possible to distinguish two sub‐types, W2 and W3. Sub‐type W2 is characterized by a high‐pressure cell over North America, which is accompanied by enhanced cyclonic activity over the eastern North Pacific. Due to a broad southerly “anomalous” flow, surface air temperatures (SATs) are above normal almost everywhere over the continent. During the W3 sub‐type, the polar jet stream over North America, instead of forming a typical ridge‐trough pattern, is almost entirely zonal, thus effectively blocking an advection of cold Arctic air to the south. Cold winters tend to occur when the atmospheric circulation is more meridional (type C1). As with warm winters, there are two sub‐types of circulation, C2 and C3. In the case of C2, the jet stream loops southward over the western part of North America, but its northern excursion over the eastern part is suppressed. In this situation, the probability of a cold winter is higher for Lake Superior than for the lower Great Lakes. Sub‐type C3 is characterized by an amplification of the climatological ridge over the Rockies and the trough over the East Coast. The strongest negative SAT anomalies are located south of the Great Lakes basin, so that the probability of a cold winter is higher for the lower Great Lakes than for Lake Superior.  相似文献   

Morphology of the secondary cosmic microwave background anisotropies: the key to 'smouldering' reionization     

Nickolay Y. Gnedin  Sergei F. Shandarin 《Monthly notices of the Royal Astronomical Society》2002,337(4):1435-1440

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Spectra of ocean-bottom seismic noise in the 0.01–10 Hz range     

Thomas A. Dozorov  Sergei L. Soloviev 《Geophysical Journal International》1991,106(1):113-121

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