A photometric study of the bright stars in M33

TheUBV photometry of 105 bright stars and theU magnitudes of 36 bright stars in M33 taken by the 2 m RCC telescope of the Rozhen Observatory at the Bulgarian Academy of Sciences were used to obtain colour-magnitude and colour-colour diagrams. A criterion forV, B-V, andU-B is suggested which facilitates the separation of the member stars from the foreground stars. The vast majority of the bright blue stars with strong negativeU-B are M33 members. The existence of objects with an unusual combination of colours (B-V>0.5 and strong negativeU-B) has been confirmed.     

On the 75-day cepheid and the envelope of the period-amplitude diagram in M31

On the basis of 30 observations the period of the new cepheid in M31,P=75.487 is obtained. Ths cepheid has an extremely long period and gives a possibility to determine the period-amplitude envelope toward the long-period region in M31 galaxy. A comparison of the period-amplitude diagrams in various galaxies is made.     

Solar flares,magnetic clouds,and geomagnetic storms

Firstly, semi-empirical distributions of solar wind proton number density and velocity ordered around the Heliospherical Current Sheet (HCS) of the inner heliosphere are considered. Then, the velocity profiles of flare-generated Coronal Mass Ejections (CMEs) running through the inhomogeneous heliosphere are calculated. They show that the velocities strongly depend on flare positions with respect to the HCS. Finally, a specific mutual flare-HCS-Earth location leading to a strong geomagnetic storm is deduced from calculations and supported by a few real events of solar-terrestrial physics.     

Dynamics of hydromagnetic clouds from powerful solar flares

At present two complementary approaches to calculations of flare-generated interplanetary disturbances are beeing developed. One of them is based on Parker's model with one end of every field line rooted at the Sun and the other end somewhere in outer space (Wu et al., 1983). Another approach is based on Morrison's closed-cloud hypothesis. In this paper the dynamics of flare-generated hydromagnetic oblate clouds in the solar corona and interplanetrary space is developed. Magnetic buoyancy, gravity, and momentum loss due to interactions with the interplanetary medium are taken into account. If the magnetic fields, number density, and velocity of the external plasma are known, the equations allow a simple solutions for variations of the velocity and characteristic lengths of the clouds during their motion between the Sun and the Earth. Two theoretical velocity profiles are calculated and compared with an experimental one.     

40Ar/39Ar dating of Usol'skii sill in the south-eastern Siberian Traps Large Igneous Province: evidence for long-lived magmatism

Main part of the Siberian Traps Large Igneous Province was formed in a short time-span at the Permo-Triassic boundary c. 250 Ma. New ⁴⁰Ar/³⁹Ar dating results for the Usol'skii dolerite sill in south-eastern part of the province indicate its probable emplacement c. 6 Myr after the main Permo-Triassic magmatic phase. Compilation of the published ⁴⁰Ar/³⁹Ar and U-Pb ages implies that basaltic and related magmatism lasted in total as long as 22–26 Myr. Therefore, similar to other large igneous provinces, magmatism of the Siberian Traps combined voluminous short-lived and less prominent long-lived events.     

Low-Ti melts from the southeastern Siberian Traps Large Igneous Province: Evidence for a water-rich mantle source?

Siberian Traps Large Igneous Province (STLIP) is one of the most voluminous volcanic provinces on Earth. The dominant erupted rocks are low-Ti basalts, which make up 80% by volume of the classical Noril’sk lava sequence. In the west Siberian basin and Maymecha-Kotuy area, the low-Ti basalts make up about 99% and 50% by volume, respectively. Dolerite sills in the Angara-Taseevskaya Syncline at the southeastern STLIP exhibit trace element patterns and Sr isotope ratios typical of the low-Ti basalts of the Noril’sk sequence. The most Mg-rich (MgO 9.5–11 wt%) and hence least differentiated dolerites are characterized by trace element patterns with Ta-Nb depletion, low Ce/Pb and high Sr/Pr. These trace element features are similar to water-saturated, mantle wedge-derived island arc basalts. These imply an important role of subduction fluid-derived trace elements in the source of melting beneath the Angara-Taseevskaya Syncline and other regions of the STLIP. Less magnesium rocks (MgO 3.8–6.1 wt%) with less prominent Ta-Nb depletion, higher Ce/Pb and lower Sr/Pr could be produced via olivine-plagioclase fractionation of primary high-magnesium melts.     

Convective structures in the Lofoten Basin based on satellite and Argo data

We discuss the possibility of detecting deep convection in the Lofoten Basin of the Norwegian Sea based on the eddy structures revealed from the satellite data. Satellite altimetry, SAR imagery, and MODIS satellite spectral radiometer sea-surface temperature (SST) data are used in the analysis, along with the data of oceanographic Argo floats. It is shown that the eddies identified from the satellite data correspond to the convective cells in the same region according to the data of the Argo floats. We consider several examples of the summer eddy and one winter eddy and the corresponding structures in the ocean measured by the Argo floats when they were located close to the identified eddies. As this method develops and improves, it can be used for the analysis of the dynamic of oceanic eddies in the region of the Lofoten Basin, and possibly in other regions with active deep convection.