Radial distribution of types I and II supernovae in spiral and elliptical galaxies

Photoelectric light curves of the double-lined binaries XY Cet and V380 Cyg, known to be detached systems, have been reanalyzed by means of Wood's program in order to obtain homogeneous photometric elements. Masses, radii and luminosities are given.We find that the basic elements of both components of the metallic-line binary XY Cet are consistent with current views of the metallicity phenomenon. The early-type system V380 Cyg turns out to be composed of an evolved (giant) primary and a Main Sequence companion.     

On some results of calculations of the chromospheric flare initial phase model according to the strong gasodynamic explosion theory

It is shown that while comparing the observed dependences of radius, front and plasma velocities at the time of the very initial flare phase with the family of the theoretical curves of these functions obtained according to strong explosion theory with the set of the initial density ₀ and estimated from the observations of the total flare energy E ₀, one can determine ₀ in the flare core. Knowing ₀ and E ₀, densities in the filaments responsible for the flare radiation and the effective and spectroscopic radiation volumes as well, one can determine the effective mass and the density between the filaments. The estimated mass, electron temperature, front and plasma velocities and densities both in the filaments and in the intervals are in satisfactory agreement with the modern concept of flares.     

On a method to determine the effective extension,visibility of the Balmer continuum,and the effective mass in solar flares

A method to determine the emission measure and hence the effective extension of solar flares is described. The conditions for the Balmer continuum to be visible in disk flares is also considered. The concept of the effective mass is introduced and it is shown that this mass is a little less than that of a plasma filling the whole spectroscopic volume and including thin and dense filaments and the intervals between them as well. In this connection it is necessary to have high energy electron fluxes. It is assumed that these electrons maintian a high temperature in the interval volume; being a source of powerful X-rays, such hot intervals can heat cool filaments and they in their turn reradiate in the visible and ultraviolet regions of the flare spectrum. Taking one flare as an example, we give curves of the emission measure, effective mass and numbers of hydrogen atoms in the second quantum state versus time. These curves agree qualitatively with the light curve characteristics for most of the flares.     

Velocities and birthplaces of pulsars

The values of the proper motions of 36 pulsars are analysed. It is shown that the birthplaces of pulsars are located within the OB-associations and/or in the galactic arms. Eleven cases of pulsar formation in associations, and fourteen cases of formation in the galactic arms, have been established. More precise parameters of pulsars — such as: distances, ages, spatial velocity components —, and the spatial velocity distribution of pulsars is constructed.     

Searching for Runaway OB Stars in Supernova Remnants

Searching for runaway stars in Supernova remnants gives us the possibility to estimate the mass ratio in binary systems in which there occur Supernova explosion. Such a method also gives information on portions of spectroscopic and close binaries among the stars on the main sequence with mass > 7–8 M⊙. More importantly, we can learn more about space velocities and spin periods of pulsars by this way. We have searched for runaway OB stars in central parts of 48 Supernova remnants with distances less than about 3 kpc. In 16 of the remnants in our sample, there is no candidate O or B type star and we have shown that pulsars (point sources) might be born not only in spectroscopic and close binaries. We have represented a list of stars which are candidates for runaway B type stars located in Supernova remnants. Spectroscopic investigations on these candidates could provide solutions for the problems mentioned above.__________Published in Astrofizika, Vol. 48, No. 3, pp. 393–408 (August 2005).     

Atmospheric parameters and mass distribution of DA-white dwarfs

The method of effective temperatureT _eff and logg determination for DA-white dwarfs by KSW model atmospheres is analyzed. The existence of systematic errors in logg determination, leading to lower mass values forT _eff>15000 K, is demonstrated. With due account to logg corrections, masses for 355 DA-dwarfs were evaluated. The influence of the effects of observational selection on mass distribution has been considered. These effects are connected with the fact that such selection on effects favour discovery of white dwarfs of low masses. The distribution obtained is characterized by the average mass of ～0.75M _⊙ and the distribution width of ～0.20M _⊙.     

On the lifetime of bright X-ray sources

The lifetime of massive X-ray binaries is about 2–5×10⁵ yr, close to the nuclear time scale. The lifetime of nonmassive X-ray binaries close to the thermal one is about 0.5–1×10⁷ yr. Massive systems may be conserved at supernova explosion, the probability of the conservation of nonmassive systems being 1–3×10^–3.     

Second catalogue of X-ray sources

A catalogue of X-ray sources containing 677 objects known as of 1979 September has been compiled. X-ray data collected by means of rockets, balloons, and satellites during 1964–1979 are listed. Optical and radio counterparts are suggested. The existence of the weak X-ray sources population in the Galaxy is indicated. The number of X-ray sources of each type in the Galaxy is estimated.Astrophysics and Space Science review paper.