Spectrophotometric Variability of Mira

Data from the Pulkovo spectrophotometric data base on the absolute quasimonochromatic fluxes from oCet in the 320–1080 nm range are used to determine the physical parameters of this star in different phases of its light curve. The continuum emission layer is found to expand between the phases of the cycle corresponding to the rising and falling branches of the light curve. The average expansion velocity is 32 km/s. By the time the star’s brightness has fallen by roughly three magnitudes, its radius has increased by almost a factor of three. Over this same time the temperature of the layer has fallen from 3000 K to 2200 K. For this expansion velocity, the calculated mass rate loss is ⊙ M /year.__________Translated from Astrofizika, Vol. 48, No. 2, pp. 175–189 (May 2005).     

On the influence of massless scalar and vector electromagnetic fields on the singularity character in anisotropic cosmology

It is shown that, for the scalar-tensor cosmology (STC) by Jordan-Brans-Dicke (JBD), in general anisotropic solution the oscillatory mixmaster regime near the singularity will be destroyed by the scalar source-free field and replaced by monotonousV ₃-collapse into the point or into the line and plane (only in caseG0) even in the presence of the primordial source-free electromagnetic (EM) field.     

Physical parameters of the continuum emission layer of Mira type stars. II. Radii and expansion velocities

The Pulkovo Spectrophotometric Data Base is used to determine the expansion velocities and radii of the continuum emission layers of the stars RR SCO and OMICR CET. Dependences of the radii and velocities on the phase of the variability cycle are found which agree with the known values obtained from the layers which emit line radiation. __________ Translated from Astrofizika, Vol. 50, No. 4, pp. 557–564 (November 2007).     

Microvariability and fast variability of stars. I. standard stars

This is a study of observations of the photometric quantities Vt and Bt, reported in the Hipparcos catalog, for 15 standard stars in order to search for microvariability and rapid variability in their emission. The microvariability is found to be characterized mainly by smooth fluctuations in the brightness. Changes in the magnitudes of the stars HD 28355 and HD 130109 with a period of ~150 min and an amplitude <0^m.02 appear to be caused by vertical shifts in their photospheres. Changes in the magnitudes with an amplitude of ~0^m.01 and a period of 11.4^d in the star e Eri were related to the rotation of spots. A similar microvariability period and amplitude in the star 51 Peg most likely originates in the influence of a planet.     

The Balmer discontinuities of main sequence stars. Comparison with theory

We study the relation between the magnitude of the Balmer discontinuity and the effective temperature of main sequence stars. We show that the observed Balmer discontinuities exhibit a systematic divergence from the theoretical discontinuities obtained using the Kurucz models. We discuss the possible reasons for this discrepancy.Translated fromAstrofizika, Vol. 38, No. 3, 1995.     

Spectrophotometric observations of variable stars

We present the results of our visual and near-infrared spectrophotometric observations for 77 variable stars obtained during 1971–1991 in Chile, Armenia, and Bolivia. The quasi-monochromatic, extraatmospheric fluxes from the stars are given in absolute energy units (W m^?2 m^?1) at all wavelengths of the spectral range at 2.5-nm intervals.     

Physical parameters of the semiregular variable red giant 2 Cen

This is a study of photometric data from the Hipparcos catalog and spectrophotometric observations by a group of Pulkovo observers in Bolivia of the variable star 2 Cen (V806 Cen). Fourier analysis yields a more precise value of 12.57 d for the period of the brightness variation instead of 12.0 d. Light curves constructed from the photometric data are found to have a smooth systematic variation with an amplitude on the order of 0^m.2. Short duration changes in the brightness by 0^m.1 take place over times of a few hours. The differences in the temperature and radius of the emitting layer at maximum and minimum brightness, which occur at phases of 0.00 and 0.58, respectively, are found. At the maximum the radius was smaller by 6% and the temperature was higher by 70 K; these differences may characterize the star’s pulsations.     

In quest of Paleocene global-scale transgressions and regressions: constraints from a synthesis of regional trends

Chronostratigraphically-justified records of regional transgressions and regressions are important for understanding the nature of the Paleocene shoreline shifts on a global scale. Review of previously synthesized data from 7 tectonically “stable” regions, namely the eastern Russian Platform, Northwestern Europe, Northwestern Africa, Northeastern Africa, the Arabian Platform, the northern Gulf of Mexico, and Southern Australia, allows a comparison of transgressions and regressions interpreted in these regions. No common patterns are found in the early Danian and late Selandian, which reflects small or zero eustatic fluctuations that are overwhelmed locally on coastlines by regional tectonic motions and local changes in dynamic support of surface topography by mantle flow. Sea level was stabilized during these stages by a warm climate and a lack of planetary-scale tectonic changes. We have detected a middle–late Danian regression that occurred in 5 of 7 study regions, and can be explained by glacial advance at ～62–63 Ma or by concurrent subduction of the Izanagi–Pacific ridge beneath eastern Asia. An early–middle Selandian transgression also occurred in 5 regions, probably, as a result of a hyperthermal at ～61 Ma that coincided with emplacement of large igneous provinces in the oceanic domain. Both events are characterized by significant diachroneity, which can also be explained by the influence of regional tectonic subsidence or uplift. Results of the present study permit us to propose a tentative framework for a new Paleocene eustatic curve that is constrained globally using available records of transgressions and regressions.