SN2015bh in NGC 2770: LBV core collapse in merging of binary system components     

V. P. Goranskij  E. A. Barsukova  A. F. Valeev  D. Yu. Tsvetkov  I. M. Volkov  V. G. Metlov  A. V. Zharova 《Astrophysical Bulletin》2016,71(4):422-435

We present spectroscopy and multicolor photometry for the optical transient PSN J09093496+3307204 in the galaxy NGC2770, which has afterwards been transferred into the supernova phase and got the name SN2015bh. Medium-resolution spectral observations were carried out between February 2015 to May 2016 using the focal reducer SCORPIO at the 6-m Russian telescope BTA. They were followed by by photometric observations at the BTA and six other telescopes with 0.5–1m apertures. Both at the phase of the SN impostor (2015a) and at the supernova phase (2015b), besides Balmer emissions, the strong Fe II emissions are seen in the spectrum; so, these spectra resemble those of Williams Fe II type classical novae. Taking into account circumstellar, interstellar and galactic absorption, A_V = 1.^m 14 ±0.^m 15), we determined maximum absolute magnitudes of the object to be M_V =–15.^m 0 ±0.^m 3 at the 2015a phase and of M^V =–18.^m 14 ±0.^m 30 at the 2015b phase. The light curve at the 2015b phase is similar to those of SN IIL. The supernova progenitor is a luminous blue variable (LBV) star with the powerful Hα emission. We consider several hypotheses of supernovae explosions following optical transients related with LBV. The hypothesis of core collapse of an evolved massive star interrupting the process of its merging with massive companion in a binary system (a failed luminous red nova) was chosen as the preferable one for this event.  相似文献   

Remote method of determining the coordinates of points on a planetary surface     

I. V. Barmin  V. P. Savinykh  V. Ya. Tsvetkov 《Solar System Research》2014,48(7):493-496

A method and an algorithm for determining the coordinates of points on the planetary surface are described. The coordinates are determined using photographs. To solve the problem, the spacecraft coordinates need to be determined at five trajectory points. The spacecraft trajectory is considered to be a plane. The method is applicable for determining the coordinates of points on the Earth’s surface and on the surface of other planets.  相似文献   

Distortion of the stellar velocity field parameters due to systematic variations of parallaxes over the celestial sphere     

V. V. Vityazev  A. S. Tsvetkov 《Astronomy Letters》2014,40(1):46-58

We study the effect of systematic variations in stellar parallaxes over the celestial sphere on the results of a kinematic analysis of stellar proper motions. Our approach is based on the representation of stellar parallaxes by scalar spherical harmonics and on the decomposition of stellar proper motions into a system of vector spherical harmonics. We derive theoretical relations that relate the coefficients of the decomposition of stellar proper motions into toroidal and spheroidal harmonics to the coefficients of the decomposition of stellar parallaxes into scalar spherical harmonics. We have established that the systematic variations of parallaxes over the celestial sphere distort all parameters of the linear Ogorodnikov-Milne model and can be responsible for the appearance of beyond-the-model harmonics. We have performed a kinematic analysis of the proper motions of blue-white and red giants based on Hipparcos data. The parallaxes of blue-white giants show a strong dependence on Galactic latitude (with predominant contraction along the Galactic equator). In contrast, the deviations of the parallaxes from the mean for red giants are localized only in two regions of the celestial sphere. For these samples, the effect of parallax variations over the celestial sphere on kinematic parameters has turned out to be comparable to their rms errors. The global solutions performed using both samples have revealed strong beyond-the-model kinematic effects described by second-order toroidal harmonics and third-order spheroidal harmonics. Using the solutions performed separately in the northern and southern Galactic hemispheres, we have established that not the systematic variations of parallaxes over the celestial sphere but the retardation of Galactic rotation with increasing distance of stars from the principal Galactic plane is mainly responsible for the appearance of these harmonics. Based on these samples of stars, we have estimated the magnitude of the vertical Galactic rotation velocity gradient to be 18.0±2.9 and 22.7±2.2 km s^?1 kpc^?1, respectively.  相似文献   

Flare stars in the pleiades. V     

L. V. Mirzoyan  O. S. Chavushyan  L. K. Erastova  G. B. Oganyan  N. D. Melikyan  R. Sh. Natsvlishvili  M. K. Tsvetkov 《Astrophysics》1977,13(2):105-116

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The SAI catalog of supernovae and radial distributions of supernovae of various types in galaxies     

D. Yu. Tsvetkov  N. N. Pavlyuk  O. S. Bartunov 《Astronomy Letters》2004,30(11):729-736

We describe the Sternberg Astronomical Institute (SAI) catalog of supernovae. We show that the radial distributions of type-Ia, type-Ibc, and type-II supernovae differ in the central parts of spiral galaxies and are similar in their outer regions, while the radial distribution of type-Ia supernovae in elliptical galaxies differs from that in spiral and lenticular galaxies. We give a list of the supernovae that are farthest from the galactic centers, estimate their relative explosion rate, and discuss their possible origins.  相似文献   

Population i pulsating stars     

Ts. G. Tsvetkov 《Astrophysics and Space Science》1989,151(1):47-71

On the basis of our age estimations of Population I pulsating stars in our Galaxy (Tsvetkov, 1986a), the mean ages of 6 open star clusters containing 21 Delta Scuti-variables and of 8 star clusters and associations containing 13 classical cepheids, have been evaluated. These mean cluster age estimations weighted according to the probabilities for different evolutionary phases of the pulsating stars, are obtained in the evolutionary track systems of Iben (1967) and Paczyski (1970); the cluster ages are larger in the former system. Our results are compared with those obtained from various methods by other authors. Clusters with classical cepheids and with Delta Scuti-stars have ages, respectively, in the ranges 10⁷–10⁸ years and 10⁶–10⁹ years. It is shown that the use of simple period-age(-colour) relations for Population I pulsating stars gives sufficiently accurate cluster age estimations. By use of our period-age relations for classical cepheids (Tsvetkov, 1986a), the mean ages of 56 other star clusters and associations in our Galaxy, the Magellanic Clouds, and M 31 galaxy have been estimated in both systems of tracks. The results are generally in agreement with those obtained from various methods by other authors. The use of Population I pulsating stars in star clusters and associations is one of the simplest and most easily applied methods for determining cluster ages; but there are some limitations in its application.  相似文献   

Very Large Array-RATAN 600 observations of a solar active region     

V. M. Bogod  G. B. Gelfreikh  R. F. Willson  K. R. Lang  L. V. Opeikina  V. Shatilov  S. V. Tsvetkov 《Solar physics》1992,141(2):303-323

The Very Large Array (VLA) and the RATAN 600 were used to observe a solar active region on two consecutive days around the time of a partial solar eclipse in July 1990. VLA synthesis maps at 2.0, 3.5, and 6.2 cm wavelength reveal bright (T _b = 0.2 – 2.2 × 10⁶ K), compact ( = 10–40) sources above the penumbra of the leading sunspot while maps at 20 cm wavelength reveal an extended ( 4.5) looplike structure (T _b 10⁶ K) between the dominant spots. Total flux and brightness temperature spectra of both components were obtained by the RATAN at nine wavelengths between 1.7 and 21 cm. The relatively-flat spectrum of the extended emission is attributed to the optically thin thermal brems Strahlung of electrons trapped in a magnetic loop at coronal temperatures. Step-spectrum sunspot-associated emission is attributed to thermal gyroresonance radiation at different heights along the leg of a loop joining regions of opposite magnetic polarity. Comparisons with predicted distributions of gyroresonance radiation indicate that the compact sunspot-associated sources lie at heights of h = 2500–17500 km above the photosphere. Although potential fields of sufficient strength appear to exist at coronal heights, differences n the observed and predicted brightness distributions suggest some role for non-potential fields or for an inhomogeneous distribution of electron density or temperature above the sunspot.  相似文献   

Microwave radiation of solar coronal holes: Results of CrAO RI RT-22 observations in 2003–2006     

S. A. Samis’ko  L. I. Tsvetkov 《Bulletin of the Crimean Astrophysical Observatory》2008,104(1):59-66

Results of the identification of solar coronal holes (CH) with radio brightness depressions and excesses are presented, which were obtained as a result of RT-22 observations at 2.0–3.5 cm in 2004–2006. Microwave radiation inhomogeneities in CHs, quiet SUN, and small sunspots were studied using RT-22 observations of May 31, 2003; October 3, 2005; and March 29, 2006 eclipses.  相似文献   

Condor-E Spacecraft with a Synthetic Aperture Antenna and Its Capabilities     

Babokin  M. I.  Efimov  A. V.  Zaytsev  S. E.  Karpov  O. A.  Savosin  G. V.  Titov  M. P.  Tolstov  E. F.  Turuk  V. E.  Tsvetkov  O. E. 《Izvestiya Atmospheric and Oceanic Physics》2017,53(9):1205-1215

Izvestiya, Atmospheric and Oceanic Physics - The main parameters of a small spacecraft (SSC) (Condor-E) and its onboard radar with a synthetic aperture antenna (SAR) are presented in the paper. Two...  相似文献   

Valent state and coordination of cobalt Ions in beryl and chrysoberyl crystals     

V. P.?Solntsev  E. G.?Tsvetkov  A. I.?Alimpiev  R. I.?MashkovtsevEmail author 《Physics and Chemistry of Minerals》2004,31(1):1-11

We have studied the polarized optical absorption and EPR spectra of Co-doped beryls grown by hydrothermal, flux, and gas-transport methods, and chrysoberyl grown by the Czochralski method. In beryls three groups of bands, belonging to three various Co centers, were distinguished by analysis of the absorption band intensities. The first group, bands with maxima at 22 220 (E c), 17 730 (E c), and 9090 (E c), 7520 (E c) cm^–1 are due to Co²⁺ in octahedral site of Al³⁺. The second group is bands at 18 940, 18 250, 17 700 (E c), 18 300, 17 700, 17 000 (E c) and 8830 (E c), 7350 (E c) cm^–1 and 5320 (E c), 3880 (E c) cm^–1, which are caused by Co²⁺ in tetrahedral site of Be²⁺. A weak wide band in flux and gas-transport beryl in the region of 12 500–8300 cm^–1 (E , c) is related to Co³⁺ in octahedral Al³⁺ site. In hydrothermal beryl, bands 13 200 (E c), 10 900 (E c), and 8500 (E c) cm^–1 are caused by an uncontrolled impurity of Cu²⁺ ions. For Co-doped chrysoberyl one type of center of Co has been established: Co²⁺ in the octahedral site of Al³⁺. In the approximation of the trigonal field with regard to Trees correction, the energy levels of Co²⁺ 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 explained well in terms of the spin-orbit interaction.  相似文献