Biostratigraphy of Jurassic-Cretaceous boundary sediments in the Eastern Crimea     

V. V. Arkad’ev  A. A. Fedorova  Yu. N. Savel’eva  E. M. Tesakova 《Stratigraphy and Geological Correlation》2006,14(3):302-330

The Dvuyakornaya Formation section in the eastern Crimea is described and subdivided into biostratigraphic units based on ammonites, foraminifers, and ostracodes. The lower part of the formation contains first discovered ammonites of the upper Kimmeridgian (Lingulaticears cf. procurvum (Ziegler), Pseudowaagenia gemmellariana Olóriz, Euvirgalithacoceras cf. tantalus (Herbich), Subplanites sp.) and Tithonian (?(Lingulaticeras efimovi (Rogov), Phylloceras consaguineum Gemmellaro, Oloriziceras cf. schneidi Tavera, and Paraulacosphinctes cf. transitorius (Oppel)). Based on the assemblage of characteristic ammonite species, the upper part of the formation is attributed to the Berriasian Jacobi Zone. Five biostratigraphic units (zones and beds with fauna) distinguished based on foraminifers are the Epistomina ventriosa-Melathrokerion eospirialis Beds and Anchispirocyclina lusitanica-Melathrokerion spirialis Zone in the upper Kimmeridgian-Tithonian, the Protopeneroplis ultragranulatus-Siphoninella antiqua, Frondicularia cuspidiata-Saracenaria inflanta zones, and Textularia crimica Beds in the Berriasian. The Cyrherelloidea tortuosa-Palaeocytheridea grossi Beds of the Upper Jurassic and Raymoorea peculiaris-Eucytherura ardescae-Protocythere revili Beds of the Berriasian are defined based on ostracodes. A new biostratigraphic scale is proposed for the upper Kimmeridgian-Berriasian of the eastern Crimea. The Dvyyakornaya Formation sediments are considered as deepwater facies accumulated on the continental slope.  相似文献   

A Pulsar Time Scale Based on Parkes Observations in 1995–2010     

A. E. Rodin  V. A. Fedorova 《Astronomy Reports》2018,62(6):378-382

Timing of highly stable millisecond pulsars provides the possibility of independently verifying terrestrial time scales on intervals longer than a year. An ensemble pulsar time scale is constructed based on pulsar timing data obtained on the 64-m Parkes telescope (Australia) in 1995–2010. Optimal Wiener filters were applied to enhance the accuracy of the ensemble time scale. The run of the time-scale difference PT_ens?TT(BIPM2011) does not exceed 0.8 ± 0.4 μs over the entire studied time interval. The fractional instability of the difference PT_ens?TT(BIPM2011) over 15 years is σ _z = (0.6 ± 1.6) × 10^?15, which corresponds to an upper limit for the energy density of the gravitational-wave background Ω _g h² ~ 10^?10 and variations in the gravitational potential ~10^?15 Hz at the frequency 2 × 10^?9 Hz.  相似文献   

Destruction of a Star during the Evolution of a Star + Supermassive Black Hole System     

Fedorova  A. V.  Tutukov  A. V. 《Astronomy Reports》2021,65(2):95-109

Astronomy Reports - Stars located closely to supermassive black holes (SMBHs) can, under certain conditions, form close binary systems with the SMBHs, in which the star may fill the Roche lobe and...  相似文献   

Evolution of stars with high metallicities     

A. V. Tutukov  A. V. Fedorova 《Astronomy Reports》2001,45(11):882-887

We have calculated evolutionary tracks for stars with high abundances of heavy elements. An abundance increase from the solar level (～0.02) to 0.1 (for ΔY/ΔZ=0–2.4), which corresponds to the central regions of the disk components of giant galaxies, shifts the main sequence towards lower effective temperatures; however, it does not appreciably affect either the luminosity of the stars or their lifetime on the main sequence. Increasing the heavy-element abundance to 0.2 for ΔY/ΔZ=2.4 shifts the main sequence towards higher effective temperatures, appreciably increases the luminosity of the stars, and substantially accelerates their evolution.  相似文献   

Balloon investigations of radiative fluxes in the free atmosphere     

K. Y. Kondratiev  I. Y. Badinov  G. N. Gaevskaya  G. A. Nikolsky  M. P. Fedorova 《Pure and Applied Geophysics》1964,58(1):187-203

Summary The present research considers the vertical profiles of the radiation balance and its components for summer and autumn seasons measured by standard actinometric instruments fixed on free balloons and gives the values of radiational temperature changes in the layers of 1000 to 500 and 1000 to 20 mb.  相似文献   

Variations of the X-ray INTEGRAL spectrum of the active galactic nucleus of NGC 4945     

E. V. Fedorova  V. I. Zhdanov 《Kinematics and Physics of Celestial Bodies》2016,32(4):172-180

Results of 11-year-long X-ray INTEGRAL observations of the nucleus of Seyfert galaxy NGC 4945 in the 3–500 keV range were processed. A two-component spectrum model, which includes strong radiation absorption in the Compton-thick torus around the AGN “central engine” and secondary radiation reflected from the torus walls, was used in the analysis. The following primary spectrum parameters were determined based on the data accumulated throughout the entire exposure period: photon index Γ = 1.60 ± 0.07, exponential cutoff energy E _c =157 _-22 ⁺²⁹ keV, and column density of the medium that absorbs primary radiation N _H,1 =5.0 _-0.9 ^+1.0 × 10²⁴ cm^–2. The column density of the medium absorbing reflected radiation is two orders of magnitude lower. Both the X-ray flux in the ranges of 20–40, 40–60, and 60–100 keV and the shape of the X-ray spectrum of NGC 4945 vary. The spectrum shape variations may be induced by inhomogeneities of the absorbing medium surrounding the AGN. At the same time, there is some evidence for moderate spectrum variations in the highenergy region, which may be associated with changes in the “central engine.”  相似文献   

Evolution of low-mass close binaries with orbital angular momentum losses     

A. V. Tutukov  A. V. Fedorova  É. V. Érgma  L. R. Yungel'son 《Astrophysics》1986,24(1):51-59

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Results of Modeling Sources of Magnetic Anomalies in the Earth’s Crust in the Middle Urals     

Martyshko  P. S.  Fedorova  N. V.  Rublev  A. L. 《Doklady Earth Sciences》2022,507(2):1107-1111

Doklady Earth Sciences - The results of studying the structural features of an anomalous magnetic field and modeling sources in the Earth’s crust of the Middle Ural region are presented. A...  相似文献   

Discovery of Emission Pulses from Magnetar SGR 1935+2154     

Rodin  A. E.  Fedorova  V. A. 《Astronomy Reports》2022,66(1):32-37

Astronomy Reports - In the paper, observation results of the magnetar SGR 1935+2154 at the frequency 111 MHz by the LPA (BSA) FIAN radio telescope are presented. For the search of single...  相似文献   

Formation and evolution of Ae and Be stars     

A. V. Tutukov  A. V. Fedorova 《Astronomy Reports》2007,51(10):847-862

Several scenarios for the formation of accretion and decretion disks in single and binary Ae and Be stars are proposed. It is shown that, in order for a rapidly rotating main-sequence Be star to lose mass via a disk, the star’s rotation must be quasi-rigid-body. Estimates show that such rotation can be maintained by the star’s magnetic field, which is probably a relict field. The evolution of single Be main-sequence stars is numerically simulated allowing for mass loss via the stellar wind and rotational mass loss assuming rigid-body rotation. The stellar wind is the factor that determines the maximum mass of Be stars, which is close to 30M _⊙. The evolution of Be stars in close binaries is analyzed in the approximation adopted in our scenario. Long gamma-ray bursts can be obtained as a result of the collapse of rapidly rotating oxygen—neon degenerate dwarfs—the accreting companions of Be stars—into neutron stars.  相似文献