A Search for a Globular Cluster whose Passage Through the Galactic Disk Could Induce the Formation of the Gould Belt

The distribution of sites where globular clusters have crossed the Galactic disk during the last 100 million years has been analyzed using the most recent kinematic data for 133 globular clusters (GCs). ThreeGCs (NGC 6341, NGC 7078, and ω Cen) whose distances between the positions where they crossed the Galactic disk and trajectories of the Gould Belt are less than 20% of their heliocentric distances at the crossing time (82, 98, and 96 million years ago, respectively) have been identified. For each of the clusters, this was their next to last, rather than their last, crossing of the Galactic disk. The passage of any one of these three GCs through the disk could potentially have initiated the formation of the Gould Belt.     

X-ray spectral evolution of low-mass X-ray binary GX 349+2

We present the results of a systematic investigation of spectral evolution in the Z source GX 349+2, using data obtained during 1998 with the Proportional Counter Array (PCA) on-board the RXTE satellite. The source traced a extended normal branch (NB) and flaring branch (FB) in the colour–colour diagram (CD) and the hardness-intensity diagram (HID) during these observations. The spectra at different positions of the Z-track were best fitted by a model consisting of a disc blackbody and a Comptonized spectrum. A broad (Gaussian) iron line at ∼6.7 keV is also required to improve the fit. The spectral parameters showed a systematic and significant variation with the position along the Z-track. The evolution in spectral parameters is discussed in view of the increasing mass accretion rate scenario, proposed to explain the motion of Z sources in the CD and the HID.     

First Byurakan Spectral Sky Survey. Stars of Late Spectral Types. XI. Zone -7° ≤ δ ≤ -3°

The eleventh list of faint late M and carbon type stars detected on the plates of the First Byurakan Spectral Survey in zone -7° -3° and covering about 1000 square degrees is presented. From 126 detected stars, 88 are newly discovered objects: they are 6 carbon stars, 8 carbon star candidates, and 74 M-type stars; among the latter 38 (26 PSC + 12 FSC) are unclassified IRAS sources, and one object is an unclassified ROSAT source. Distances to the 6 newly discovered early-type carbon stars are estimated. Equatorial coordinates, red magnitudes, and spectral classes determined from the Palomar E-charts are provided. The lack of optical counterparts on Palomar O and E maps for two detected late M-type stars indicates a large variability in brightnesses of these objects (amplitude not smaller than 7.0 magnitude).     

Comment on the “Analysis of the State of Stress During the 1997 Earthquake Swarm in Western Bohemia” by A. Slancová and J. Horálek (Studia geoph. et geod. 44(2000), 272–291)

Studia Geophysica et Geodaetica -     

Merging of low-mass systems and the origin of the fundamental plane

We present the preliminary results of a study of how small stellar systems merge to form larger ones. As we display the families of galaxies in the μ_e - R_e plane (effective surface brightness versus effective radius) we realize that different morphological types occupy different loci, evidencing the different physical mechanisms operating in each family. As proposed by Capaccioli et al. (1992) this diagram is the logical equivalent of the HR diagram for stars. Here we take some initial steps in understanding of how we can establish the evolutionary tracks, solely due to dynamical processes, in the μ_e - R_e plane, ultimately making a dwarf elliptical to turn into a normal elliptical galaxy. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Siberian Solar Radio Telescope: the current state of the instrument,observations, and data

The Siberian Solar Radio Telescope (SSRT) is one of the world's largest solar radio heliographs. It commenced operation in 1983, and since then has undergone several upgrades. The operating frequency of the SSRT is 5.7 GHz. Since 1992 the instrument has had the capability to make one-dimensional scans with a high time resolution of 56 ms and an angular resolution of 15 arc sec. Making one of these scans now takes 14 ms. In 1996 the capability was added to make full, two-dimensional images of the solar disk. The SSRT is now capable of obtaining images with an angular resolution of 21 arc sec every 2 min. In this paper we describe the main features and operation of the instrument, particularly emphasizing issues pertaining to the imaging process and factors limiting data quality. Some of the data processing and analysis techniques are discussed. We present examples of full-disk solar images of the quiet Sun, recorded near solar activity minimum, and images of specific structures: plages, coronal bright points, filaments and prominences, and coronal holes. We also present some observations of dynamic phenomena, such as eruptive prominences and solar flares, which illustrate the high-time-resolution observations that can be done with this instrument. We compare SSRT observations at 5.7 GHz, including computed `light curves', both morphologically and quantatively, with observations made in other spectral domains, such as 17 GHz radio images, Hα filtergrams and magnetograms, extreme-ultraviolet and X-ray observations, and dynamic radio spectra.     

Hydroextrusion as a possible mechanism for the ascent of diapirs,domes, and mantle plumes

A possible mechanism of the ascent of material within the Earth’s crust and mantle is the mechanism of hydroextrusion, i.e., the effect of squeezing of material under excess pressure. The major factors that predetermine the high plasticity of the material and its ability to produce hydroextrusions are high lithostatic pressures and temperatures. The phenomenon of hydroextrusion can be most clearly illustrated by the example of the origin of salt diapirs. The driving force of hydroextrusions of material in the crust and mantle is excess pressure, which can result from lateral differences between the densities of rocks (as is the case during the development of salt diapirs) and phase transitions associated with a volume increase. When the material of the upper mantle undergoes partial melting with the derivation of basaltic melts at depths of 60–100 km, excess pressures reach 80 MPa, whereas the plasticity limit of 20% melted rocks is no higher than 5 MPa. As a result, the partially molten material is forced from the melting region toward zones with lower lithostatic pressures. A local temperature increase in the transitional zones in the Earth’s mantle at positive dP/dT values of the phase transitions also gives rise to excess pressures, whose values can range from 100 to 800 MPa at a 0.5–3.0% volume change and which can be the driving force during the origin of mantle plumes. Original Russian Text ? V.N. Anfilogov, Yu.V. Khachai, 2006, published in Geokhimiya, 2006, No. 8, pp. 873–878.