Orbital periods of the binary sdB stars PG 0940+068 and PG 1247+554

We have used the radial velocity variations of two sdB stars previously reported to be binaries to establish their orbital periods. They are PG 0940+068 ( P =8.33 d) and PG 1247+554 ( P =0.599 d). The minimum masses of the unseen companions, assuming a mass of 0.5 M_⊙ for the sdB stars, are 0.090±0.003 M. for PG 1247+554 and 0.63±0.02 M_⊙ for PG 0940+068. The nature of the companions is not constrained further by our data.     

Temporal variability in the maternal environment and its effect on seed size and seed quality in Flourensia cernua DC. (Asteraceae).

The biological phenomenon commonly referred to as maternal effect occurs whenever the environment exerts an influence upon the mother that is later expressed in characteristics of her offsprings. For example, the environmental conditions experienced by a mother plant during flowering and fruiting can modify the quality of her descendants (seeds), and even interrupt their development. Between-year variation in minimum temperature and the classic, between-year variation in precipitation represent an unpredictable environment for winter blooming plants in arid zones. In this study, we investigated the effect of maternal environment (temperature and precipitation) on seed size and seed quality in F. cernua, over a 5-year period. Results indicated that the proportion of filled seeds, as well as their size, increased with higher absolute minimum temperatures during seed formation, and that, to a lesser extent, both the precipitation occurred during the same period and the annual precipitation also have a positive influence on seed size. In this way, environmental conditions prevailing during seed formation exerted a strong maternal effect on the size and quality of seeds produced and, probably also, in the developmental possibilities of F. cernua seedlings. This effect was subject to important, between-year variation.     

Planetary elements for 10 000 000 years

In 1950 Brouwer and van Woerkom published a secular theory of the variations of the planetary elements in analytical form. In the present paper we provide a graphical representation of this theory in the form of element plots for a time span of ten million years.     

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.     

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.     

The Martian magnetic field

The magnetic field measurements of the Mars 2, 3 and 5 spacecraft have been interpreted by Dolginov and co-workers to be consistent with an intrinsic planetary magnetic moment of 2.5 × 10²² gauss cm³. They base this interpretation mainly on the apparent size of the obstacle responsible for deflecting the solar wind, the lack of dependence of the sign of the magnetic field in the wake region of the planet on the sign of the component of the interplanetary field radially out from the sun, and an apparent encounter of the Mars spacecraft with the planetary field. When examined in detail this evidence is very suspect. A detailed criticism of the arguments by Dolginov and co-workers for an intrinsic field has appeared elsewhere. Herein we summarize this criticism and present, in an appendix, a compendium of the Mars 3 and 5 magnetic field data transformed into a coordinate system in which the details of the interaction are more easily visualized. Many of these data have not been published in this form previously.     

Opening angles, Lorentz factors and confinement of X-ray binary jets

We present a collation of the available data on the opening angles of jets in X-ray binaries, which in most cases are small (≲10°). Under the assumption of no confinement, we calculate the Lorentz factors required to produce such small opening angles via the transverse relativistic Doppler effect. The derived Lorentz factors, which are in most cases lower limits, are found to be large, with a mean >10, comparable to those estimated for active galactic nuclei (AGN) and much higher than the commonly assumed values for X-ray binaries of 2–5. Jet power constraints do not, in most cases, rule out such high Lorentz factors. The upper limits on the opening angles show no evidence for smaller Lorentz factors in the steady jets of Cygnus X-1 and GRS 1915+105. In those sources in which deceleration has been observed (notably  XTE J1550−564  and Cygnus X-3), some confinement of the jets must be occurring, and we briefly discuss possible confinement mechanisms. It is however possible that all the jets could be confined, in which case the requirement for high bulk Lorentz factors can be relaxed.     

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.