Variation in the Flare Frequency of Flare Stars. III. Flare Stars in the Orion Association

The possible variation of the flare frequency of flare stars in the Orion association is considered. It is shown that of the 23 chosen stars, each having exhibited four or more flares, a change in flare frequency at the 0.1 significance level can be suspected for 13.     

Galaxy Photometry in the Virgo Cluster. I.

In a field of about 0.6 square degrees near the centre of the Virgo cluster of galaxies a photometry in B, V, and R has been performed by means of the microphotometer of the Zentralinstitut für Astrophysik. For 84 galaxies identified in this field magnitudes, diameters, and axis ratios has been determined.     

Study of galaxies in the Lynx-Cancer void. IV. Photometric properties

We present the results of a photometric study of 85 objects from the updated sample of galaxies residing in the nearby Lynx-Cancer void. We perform our photometry on u, g, r, and i-band images of the Sloan Digital Sky Survey. We determine model-independent galaxy parameters such as the integrated magnitudes and colors, effective radii and the corresponding surface brightness values, optical radii and Holmberg radii. We analyze the radial surface brightness profiles to determine the central brightness values and scale lengths of the model disks. We analyze the colors of the outer parts of the galaxies and compare them with model evolutionary tracks computed using the PEGASE 2 software package. This allowed us to estimate the time T _SF elapsed since the onset of star formation, which turned out to be on the order of the cosmological time T ₀ for the overwhelming majority of the galaxies studied. However, for 13 galaxies of the sample the time T _SF does not exceed T ₀/2 ～ 7 Gyr, and for 7 of them T _SF ? 3.5 Gyr. The latter are mostly unevolved objects dominated by low-luminosity galaxies with M _B > ?13.2. We use the integrated magnitudes and colors to estimate the stellar masses of the galaxies.We estimate the parameter M(H I)/L _B and the gas mass fractions for void galaxies with known HI-line fluxes. A small subgroup (about 10%) of the gas-richest void galaxies with M(H I)/L _B ? 2.5 has gas mass fractions that reach 94–99%. The outer regions of many of these galaxies show atypically blue colors. To test various statistical differences between void galaxies and galaxies from the samples selected using more general criteria, we compare some of the parameters of void galaxies with similar data for the sample of 195 galaxies from the Equatorial Survey (ES) based on a part of the HIPASS blind HI survey. The compared samples have similar properties in the common luminosity interval ?18.5<M _g < ?13.5. The faintest void galaxies differ appreciably from the ES survey galaxies. However, the ES survey also contains about 7% of the so-called “inchoate” galaxies with highM(H I)/L _B ratios, most of which are located far from massive neighbors and are probably analogs of void galaxies.     

Abundances of elements of the palladium group in the atmospheres of evolved stars. I. Molybdenum

Principal Astronomical Observatory, Ukrainian Academy of Sciences. Translated from Astrofizika, Vol. 28, No. 3, pp. 595–598, May–June, 1988.     

Modeling of convective motions in the envelope of procyon. II. Asymmetry of the spectral lines

Principal Astronomical Observatory, Ukrainian Academy of Sciences. Translated from Astrofizika, Vol. 31, No. 3, pp. 589–600, November–December, 1989.     

The BM Ori System. III. The Depth of the Minimum in the Infrared

The depth of the minimum of the BM Ori eclipsing system is studied in the infrared. For this purpose, observations have been made in the JHKLM bands outside the eclipse and in the JHKL bands near the central phase of the eclipse. The depth of the minimum is found to have a complicated wavelength dependence. In the short wavelength region of the spectrum this depth decreases from the U band to the R band (λ=0.36–0.71 mm), which is explained in terms of eclipsing of the principal star by a dust cloud surrounding the companion and by the disk of the companion. In the IR the depth of the minimum increases sharply from the I to the L band (λ=0.97–3.5 mm). This effect can be explained by partial obscuring of the hot region of the dust cloud by the disk of the companion. __________ Translated from Astrofizika, Vol. 48, No. 4, pp. 565–573 (November 2005).     

Study of galaxies in the Lynx-Cancer void. II. Element abundances

In the framework of study of the evolutionary status of galaxies in the nearby Lynx-Cancer void, we present the results of the SAO RAS 6-m telescope spectroscopy for 20 objects in this region. The principal faint line [Oiii]λ4363 Å, used to determine the electron temperature and oxygen abundance (O/H) by the classicalmethod, is clearly detected in only about 2/3 of the studied objects. For the remaining galaxies this line is either faint or undetected. To obtain the oxygen abundances in these galaxies we as well apply the semi-empirical method by Izotov and Thuan, and/or the empirical methods of Pilyugin et al., which are only employing the intensities of sufficiently strong lines. We also present our O/H measurements for 22 Lynx-Cancer void galaxies, for which the suitable Sloan Digital Sky Survey (SDSS) spectra are available. In total, we present the combined O/H data for 48 Lynx-Cancer void galaxies, including the data adopted from the literature and our own earlier results. We make a comparison of their locations on the (O/H)-M_B diagram with those of the dwarf galaxies of the Local Volume in the regions with denser environment. We infer that the majority of galaxies from this void on the average reveal an about 30% lower metallicity. In addition, a substantial fraction (not less than 10%) of the void dwarf galaxies have a much larger O/H deficiency (up to a factor of 5). Most of them belong to the tiny group of objects with the gas metallicity Z ⊙/20 or 12+log(O/H)?7.35. The surface density of very metal-poor galaxies (Z ⊙/10) in this region of the sky is 2–2.5 times higher than that, derived from the emission-line galaxy samples in the Hamburg-SAO and the SDSS surveys. We discuss possible implications of these results for the galaxy evolution models.     

Change in entropy of non-spinning black holes w.r.t. the radius of event horizon in XRBs

The present research paper discusses the derivation for the change in entropy of Non- spinning black holes with respect to the change in the radius of event horizon applying the first law of black hole mechanics ( $\delta M = \frac{\kappa}{8\pi} \delta A + \varOmega\delta J - \upsilon\delta Q$ ) with the relation for the change in entropy δS=8πMδM. When the work is further extended with proper operation, the entropy of black hole is obtained almost the same as the Bekenstein-Hawking entropy of black hole. This is the entirely new method to obtain the change in entropy of Non-spinning black holes w.r.t. the radius of event horizon and Hawking entropy of black hole. We have also calculated their values for different types of test non-spinning black holes having masses 5–20M _⊙ found in X-ray binaries (Narayan, gr-qc/0506078v1, 2005).     

Abundances of elements of the palladium group in the atmospheres of evolved stars. II. Ruthenium

Principal Astronomical Observatory, Ukrainian Acadey of Sciences. Translated from Astrofizika, Vol. 32, No. 2, pp. 231–234, March–April, 1990     

The Cosmological Scalar in the Jordan-Brans-Dicke Theory. II.

Cosmological solutions are examined in the proper representation of the JBD theory with a dominant nonminimally coupled scalar field. It is shown that only the introduction of a cosmological scalar that transforms to the ordinary cosmological constant in the Einstein representation enables a phase of evolution with a uniform and then an accelerated expansion of the universe over cosmological time scales. __________ Translated from Astrofizika, Vol. 48, No. 4, pp. 633–640 (November 2005).     

Structural Investigations in the Central Part of the Coma Cluster on the Base of Equidensity Diagrams. I.

On the base of a photographic plate in system V, which was taken with the 134/200/400 cm Schmidt camera of the Karl-Schwarzschild-Observatorium Tautenburg maximal diameters of galaxies in the centre of the Coma cluster are determined by photographic equidensitometry. An other system of diameters is determined for medium densities of the objects. The results are compared with ROOD and BAUM'S who derived the diameters by visual measurements on plates taken with the 5-metre telescope of the Hale Observatories. Both statistics contain galaxies up to 19^m. They are complete up to 17^m.5. It is pointed out that the Tautenburg diameters are in the mean 3 times larger than those derived by ROOD and BAUM. Diameter-magnitude diagrams and ellipticities of the objects are derived, further photometric corrections for tilted objects. For describing the general structure of the cluster diameter functions are derived instead of magnitude functions. The accuracy of a brightness determination by the equidensity method from the diameter-magnitude diagrams is nearly twice better than according to ROOD and BAUM.     

Vertical Chromium Distribution in the Atmospheres of CP Stars. II. Modeling

Vertical chromium distributions in the atmospheres of several Ap and Am stars are fitted using detailed modeling of the profiles of CrII lines. The vertical distributions obtained for Ap stars are consistent with Babel's results of an investigation of Cr lines in the spectrum of the Ap star 53 Cam. It is shown that the observational data cannot be interpreted in terms of the hypothesis that microturbulent velocity varies with depth.