Dependence of the SCR proton flux estimate on radio burst parameters     

E. A. Isaeva  V. F. Melnikov  L. I. Tsvetkov 《Bulletin of the Crimean Astrophysical Observatory》2010,106(1):26-30

We present results suggesting that the accuracy of estimating the solar cosmic-ray (SCR) proton flux from μ-burst parameters is much higher for proton events characterized by a low level of post-burst increase (PBI) in the μ-burst flux, a powerful decametric (DCM) component, and a small time shift (Δt < 9 min) of the DCM burst maximum relative to the μ-burst maximum. These three parameters are probably related between themselves, since events characterized by a small Δt have a very low PBI level. We show that the accuracy of estimating the proton flux depends to a greater extent on Δt than on the intensity of the DCM component. For approximately half of the events from the investigated sample, the accuracy of estimating the proton flux approaches the maximum possible accuracy from μ-burst parameters.  相似文献   

Observations of five supernovae in 1995–1997     

D. Yu. Tsvetkov  N. N. Pavlyuk  E. P. Pavlenko 《Astronomy Reports》2001,45(7):527-537

We present the results of photometric observations of the type Ia supernovae SN 1995al, 1996bo, 1996bk, the type Ib/c supernova SN 1997X, and the type II supernova SN 1996an. The photometric characteristics of SN 1995al are close to the average for type Ia supernovae. Our analysis has revealed possible peculiarities in the light-curve shape and deviations from the average photometric parameters for SN 1996bk and 1996bo. Sn 1996an probably belongs to type IIP. The light curve of SN 1997X resembles that of the type Ic supernova SN 1994I. Light-curve parameters and absolute magnitude estimates are presented.  相似文献   

Variations of microwave emission from solar active regions     

G. B. Gelfreikh  Yu. T. Tsap  Yu. G. Kopylova  T. B. Goldvarg  Yu. A. Nagovitsyn  L. I. Tsvetkov 《Astronomy Letters》2004,30(7):489-495

Based on observational data obtained with the RT-22 Crimean Astrophysical Observatory radio telescope at frequencies of 8.6 and 15.4 GHz, we investigate the quasi-periodic variations of microwave emission from solar active regions with periods T_p<10 min. As follows from our wavelet analysis, the oscillations with periods of 3–5 min and 10–40 s have the largest amplitudes in the dynamic power spectra, while there are virtually no oscillations with T_p<10 s. Our analysis shows that acoustic modes with T_p?1 min strongly dissipate in the lower solar corona due to thermal conduction losses. The oscillations with T_p=10–40 s are associated with Alfvén disturbances. We analyze the influence of acoustic and Alfvén oscillations on the thermal mechanisms of microwave emission in terms of the homogeneous model. We discuss the probable coronal heating sources.  相似文献   

Coordination and valent state of nickel ions in beryl and chrysoberyl crystals     

V. P. Solntsev  E. G. Tsvetkov  A. I. Alimpiev  R. I. Mashkovtsev 《Physics and Chemistry of Minerals》2006,33(5):300-313

We have studied the polarized optical absorption and the EPR spectra of Ni-doped beryls grown by hydrothermal, flux and gas-transport methods, and chrysoberyl grown by the Czochralski and flux methods. In beryls, three groups of bands belonging to three various Ni centres were distinguished by analysis of the absorption band intensities. The first group, bands with maximums at 21740 (E ⊥ c), 17240 (E || c) and 9260 (E ⊥ + || c), 7140 (E || + ⊥ c) cm⁻¹, are due to Ni³⁺ in octahedral Al³⁺ site. The second group is bands at 25640 (E ⊥ c), 22220 (E || c) and 13520 (E || + ⊥ c), 13160 (E ⊥+ || c) cm⁻¹ and 8930 (E ⊥ + || c), 7460 (E || c) cm⁻¹, which are caused by Ni²⁺ in octahedral Al³⁺ site. Weak wide bands at 17540 (E ⊥ c), 15500 (E || c) cm⁻¹ and 6580 (E || + ⊥ c), 5950 (E || c) cm⁻¹ are related to Ni²⁺ in tetrahedral Be²⁺ site. The occurrence of Ni ions in Be²⁺ site is proved by the EPR spectra of ^1VNi⁺ in γ-irradiated samples. According to the spectra of optical absorption of Ni-doped chrysoberyl, two types of Ni centres have been established: Ni³⁺ and Ni²⁺ ions in octahedral Al³⁺ sites. From the EPR spectra of the X-ray irradiated crystals BeAl₂O₄: Ni, it follows that 68% of Ni⁺ ions occupy octahedral Al³⁺ sites with mirror symmetry and 32% are in Al³⁺ sites with inversion symmetry. In the approximation of trigonal field with regard to Trees correction, the energy levels of Ni³⁺ and Ni²⁺ have been calculated in octahedral and tetrahedral coordination. There is good agreement between the obtained experimental and calculated data. The polarization dependence of the optical absorption bands is well explained in terms of the spin–orbit interaction.  相似文献   

New Hα-emission stars in the region of the nebulae IC 5068-70 and NGC 7000     

M. K. Tsvetkov 《Astrophysics》1975,11(4):389-394

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Kinematic analysis of stellar radial velocities by the spherical harmonics     

V. V. Vityazev  A. S. Tsvetkov  D. A. Trofimov 《Astronomy Letters》2014,40(11):713-723

A method for a kinematic analysis of stellar radial velocities using spherical harmonics is proposed. This approach does not depend on the specific kinematic model and allows both low-frequency and high-frequency kinematic radial velocity components to be analyzed. The possible systematic variations of distances with coordinates on the celestial sphere that, in turn, are modeled by a linear combination of spherical harmonics are taken into account. Theoretical relations showing how the coefficients of the decomposition of distances affect the coefficients of the decomposition of the radial velocities themselves have been derived. It is shown that the larger the mean distance to the sample of stars being analyzed, the greater the shift in the solar apex coordinates, while the shifts in the Oort parameter A are determined mainly by the ratio of the second zonal harmonic coefficient to the mean distance to the stars, i.e., by the degree of flattening of the spatial distribution of stars toward the Galactic plane. The distances to the stars for which radial velocity estimates are available in the CRVAD-2 catalog have been decomposed into spherical harmonics, and the existing variations of distances with coordinates are shown to exert no noticeable influence on both the solar motion components and the estimates of the Oort parameter A, because the stars from this catalog are comparatively close to the Sun (no farther than 500 pc). In addition, a kinematic component that has no explanation in terms of the three-dimensional Ogorodnikov-Milne model is shown to be detected in the stellar radial velocities, as in the case of stellar proper motions.  相似文献   

Population i pulsating stars     

Ts. G. Tsvetkov 《Astrophysics and Space Science》1993,203(2):289-303

Six ways for obtaining approximate period-luminosity (P-L) relations for classical cepheids and Delta Scuti variables are presented. Three out of these ways were earlier schematically considered by J.P. Cox (1980, 1985). It was proceeded from certain results derived from the study of stellar pulsation and evolution, by using some simple considerations and simplifying assumptions. The expressions obtained for the coefficients of these approximate P-L relations, were used to estimate the slopes and the zero-points. In addition, it was evaluated the influence of both different modes of radial pulsations and variations of Population I chemical composition on the zero-points. The results satisfactorily agree with those derived from observations or accurate theoretical calculations.  相似文献   

Radial distributions of gamma-ray bursts and type Ib/c supernovae in galaxies     

D. Yu. Tsvetkov  S. I. Blinnikov  N. N. Pavlyuk 《Astronomy Letters》2001,27(7):411-415

Data on the positions of gamma-ray bursts (GRBs) in galaxies are used to construct the radial distributions of their surface density. The gradient in GRB surface density is shown to decrease sharply at a galactocentric distance equal to the effective galactic radius. In central galactic regions, the GRB density distribution agrees with the galactic surface-brightness distribution; in outer regions, the GRB density decreases more slowly than does the surface brightness. Based on improved statistics, we analyze the radial distribution of type Ib/c supernovae. We show that it differs insignificantly from the distributions of other types of supernova and exhibits a much closer similarity to the distribution of star-forming regions than do GRBs. Although the statistics for GRBs is poor, the deviation of their distribution from the distribution of active star-forming regions in nearby galaxies seems to have been firmly established. A correlation of GRBs with the distribution of dark matter in outer galactic regions is not ruled out.  相似文献   

Supernova 2002bo: inadequacy of the single parameter description     

S. Benetti  P. Meikle  M. Stehle  G. Altavilla  S. Desidera  G. Folatelli  A. Goobar  S. Mattila  J. Mendez  H. Navasardyan  A. Pastorello  F. Patat  M. Riello  P. Ruiz-Lapuente  D. Tsvetkov  M. Turatto  P. Mazzali  W. Hillebrandt 《Monthly notices of the Royal Astronomical Society》2004,348(1):261-278

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Spectral analysis of the multiple-altitude anomalous geomagnetic field     

Yu. P. Tsvetkov  V. V. Ivanov  V. G. Petrov  S. V. Filippov  O. M. Brekhov 《Geomagnetism and Aeronomy》2016,56(6):774-780

The spectra of the anomalous geomagnetic field measured at ground and balloon (30 km) altitudes were analyzed. The ground-based data were adapted from a map of the anomalous magnetic field of the Earth. A balloon surveys was carried out by the authors. It has been shown that the ground and balloon spectra of the anomalous magnetic field of the Earth substantially differ. Suppositions explaining the differences in the obtained spectra have been suggested.  相似文献