The flare star PP Ori

We give the results of photographic, photoelectric, and spectral observations of the flare star PP Ori. The 109 photographic observations used, which were obtained on the 40 Schmidt telescope of the Byurakan Observatory over a period of about 20 years, and four spectra obtained on the same telescope with a4° objective prism show no variation in brightness. Photoelectric observations in the UBVR bands using the 50cm and 60cm telescopes of the high-altitude Maidanak station of the Tashkent Astronomical Institute in 1987 and 1989 give grounds for suspecting a variation in brightness much larger than observational errors. Spectral observations of the star PP Ori made on the 2.6m telescope of the Byurakan Observatory show weak H emission. The results of all these observations show that PP Ori is an Orion variable of spectral class K7-M0 with absolute visual magnitude7 ^m 5–8 ^m 5.Translated fromAstrofizika, Vol. 38, No. 2, 1995.     

Model atmosphere and kinematical analyses of early-type stars from the Edinburgh–Cape Survey

We present high-resolution spectroscopic observations of 21 B-type stars, selected from the Edinburgh–Cape Blue Object Survey. Model atmosphere analyses confirm that 14 of these stars are young, main-sequence B-type objects with Population I chemical compositions. The remaining seven are found to be evolved objects, including subdwarfs, horizontal branch and post-AGB objects. A kinematical analysis shows that all 14 young main-sequence stars could have formed in the disc and subsequently been ejected into the halo. These results are combined with the analysis of a previous subsample of stars taken from the Survey. Of the complete sample, 31 have been found to be young, main-sequence objects, with formation in the disc, and subsequent ejection into the halo, again being found to be a plausible scenario.     

Relevance of Pentane- and Hexane-Utilizing Bacterial Indicators for Finding Hydrocarbon Microseepage: A Study from Jamnagar Sub-basin, Saurashtra, Gujarat, India

Mesozoic sediments are source rocks for nearly half the world’s hydrocarbon reserves. Hence, there is great interest in the oil industry to know the trap and sub-trappean sediment thickness and their extent in the trap covered regions of Jamnagar study area. The microbial prospecting method is applied in the Jamnagar sub-basin, Gujarat for evaluating the prospects for hydrocarbon exploration by investigating the anomalous abundance of n-pentane- and n-hexane-oxidizing bacteria of this area. A total of 150 near-surface soil samples were collected in Jamnagar sub-basin, Gujarat for the evaluation of hydrocarbon resource potential of the basin. In this study, bacterial counts for n-pentane-utilizing bacteria range between 1.09 × 10² and 9.89 × 10⁵ cfu/g and n-hexane-utilizing bacteria range between 1.09 × 10² and 9.29 × 10⁵ cfu/g. The adsorbed hydrocarbon gases consisting of ethane plus hydrocarbons (ΣC₂₊) of 1–977 ppb and n-pentane (nC₅) of 1–23 ppb. The integrated geomicrobial and adsorbed soil gas studies showed the anomalous hydrocarbon zones nearby Khandera, Haripur, and Laloi areas which could probably aid to assess the true potential of the basin. Integrated geophysical studies have shown that Jamnagar sub-basin of Saurashtra has significant sediment thickness below the Deccan Traps and can be considered for future hydrocarbon exploration.     

Band Selection for Hyperspectral Image Classification Using Mutual Information

Spectral band selection is a fundamental problem in hyperspectral data processing. In this letter, a new band-selection method based on mutual information (MI) is proposed. MI measures the statistical dependence between two random variables and can therefore be used to evaluate the relative utility of each band to classification. A new strategy is described to estimate the MI using a priori knowledge of the scene, reducing reliance on a "ground truth" reference map, by retaining bands with high associated MI values (subject to the so-called "complementary" conditions). Simulations of classification performance on 16 classes of vegetation from the AVIRIS 92AV3C data set show the effectiveness of the method, which outperforms an MI-based method using the associated reference map, an entropy-based method, and a correlation-based method. It is also competitive with the steepest ascent algorithm at much lower computational cost     

A geographical analysis of the Atalanti alluvial plain and coastline as the location of a potential tourist site, Bronze through Early Iron Age Mitrou, East-Central Greece

Tourism accounts for 15% of Greece’s gross domestic product. In the wake of a struggling economy many of Greece’s coastal villages have turned to tourism to supplement local economies. Preliminary analysis of structural and cultural materials recovered from an excavation on Mitrou, a small islet near the coastal village Tragana located 140 km north of Athens has established the site’s contribution to a fuller understanding of settlement practices in Central Greece from the end of the Bronze Age through the Early Iron Age. The site’s historic importance combined with its scenic coastal setting has considerable potential to be developed into an important tourist site. The physical geography of the region is the product of the complex interaction of coastal, alluvial, fluvial, and seismic processes. This investigation integrates the archaeological material with a geographical analysis employing a variety of geographical techniques (soil and sediment analysis, past climatic data, environmental surveys, and geospatial modeling) to reconstruct the geomorphological history of the site and to evaluate the area as a potential tourist site.     

A Multifrequency Study of Five Large Radio Galaxies

We present the results of GMRT and VLA observations of five large radio sources over a wide frequency range to investigate their structural and spectral asymmetries. The hot-spot brightness ratios suggest intrinsic source asymmetries, while the spectral indices show evidence of re-acceleration of particles.     

Book reviews

Astrophysics and Space Science -     

Derivation of density and temperature from the Cassini–Huygens CAPS electron spectrometer

In this paper we present two methods to derive electron fluid parameters from the CAPS–ELS spectrometer on board the Cassini spacecraft currently in orbit around Saturn. In the first part of the paper we give a basic overview of the instrument and describe the challenges inherent in the derivation of density and temperature values using these techniques. We then describe a method to calculate electron moments by integrating the particle distribution function. We also describe a second technique in which we fit the electron energy spectrum with a Gaussian curve and use the peak energy of this curve to derive density and temperature values. We then compare the two methods with particular emphasis on their application to Cassini SOI observations in the saturnian environment and point out the limitations of the two techniques. We will show that results from the two very different methods are in agreement when the physical properties of the environment and of the observed electron populations have been inferred from inspection of the raw data. Finally we will suggest future developments that will remove these limitations.     

Variation in the flare activity of the star UV Ceti

This is an analysis of the dependence of the flare activity of the well known flare star UV Ceti on the linear distance between the components of this binary system. It is shown that its flaring activity clearly depends on the mutual distance of the components, while this kind of variability is not seen in isolated flare stars.