An asymmetric relativistic model for classical double radio sources

There is substantial observational evidence against the symmetric relativistic model of FR II radio sources. An asymmetric relativistic model is proposed which takes account of both relativistic effects and intrinsic/environmental asymmetries to explain the structural asymmetries of their radio lobes. A key parameter of the model is the jet-side of the double sources, which is estimated for 80 per cent of the FR II sources in the 3CRR complete sample. Statistical analyses of the properties of these sources show that the asymmetric model is in agreement with a wide range of observational data, and that the relativistic and intrinsic asymmetry effects are of comparable importance. Intrinsic/environmental asymmetry effects are more important at high radio luminosities and small physical scales. The mean translational speed of the lobes is found to be     consistent with the speeds found from spectral ageing arguments. According to a Gaussian model, the standard deviation of the distribution of v _lobe is σ _{v l}=0.04 c . The results are in agreement with an orientation-based unification scheme in which the critical angle separating the radio galaxies from quasars is about 45°.     

Surface images of the short period contact binary AE Phe

We present high resolution Doppler images of the short period (P = 0.362 d) contact binary AE Phe. Using least squares deconvolution, we make use of the information content of the several thousand lines in each échelle spectrum to obtain the necessary S/N and time resolution required to resolve individual starspot features. A single pair of rotationally broadened profiles (free of sidelobes due to blending) with a typical S/N of 3000 ‐ 4000 per spectrum is thus obtained. With 300 sec exposures we achieve a cadence of 350 sec which is equivalent to sampling the rotation phase every 4°. We derive images for four nights of data which reveal starspots at most latitudes on both components of the common envelope system. Individual starspots evolve significantly on very short timescales, of order one day; significantly faster than the week timescales found on active single stars and the Sun. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Chandra observation of the X-ray environment and jet of 3C 31

We have used a deep Chandra observation of the central regions of the twin-jet Fanaroff–Riley class I (FRI) radio galaxy 3C 31 to resolve the thermal X-ray emission in the central few kpc of the host galaxy, NGC 383, where the jets are thought to be decelerating rapidly. This allows us to make high-precision measurements of the density, temperature and pressure distributions in this region, and to show that the X-ray emitting gas in the centre of the galaxy has a cooling time of only  5×10⁷ yr  . In a companion paper, these measurements are used to place constraints on models of the jet dynamics.
A previously unknown one-sided X-ray jet in 3C 31, extending up to 8 arcsec from the nucleus, is detected and resolved. Its structure and steep X-ray spectrum are similar to those of X-ray jets known in other FRI sources, and we attribute the radiation to synchrotron emission from a high-energy population of electrons. In situ particle acceleration is required in the region of the jet where bulk deceleration is taking place.
We also present X-ray spectra and luminosities of the galaxies in the Arp 331 chain of which NGC 383 is a member. The spectrum and spatial properties of the nearby bright X-ray source 1E 0104+3153 are used to argue that the soft X-ray emission is mostly due to a foreground group of galaxies rather than to the background broad absorption-line quasar.     

The Velocity Field and Kinematics of the Galaxy NGC 784 in the Hα Line

In this paper we present the H map, the 2D velocity field and the rotation curve of the galaxy NGC 784 obtained with the ByuFOSC2 scanning Fabry-Perot interferometer, attached at the prime focus of the 2.6-m telescope of Byurakan Observatory. The H image shows several HII condensations along the major axis of the galaxy. The galaxy has an asymmetric distribution of the H emission. The rotation curve is quite symmetric with a low gradient in the central part of the galaxy.     

1961-2008年中国西南地区极端气候变化幅度的海拔效应(英文)

A total of 12 indices of temperature extremes and 11 indices of precipitation ex-tremes at 111 stations in southwestern China at altitudes of 285-4700 m were examined for the period 1961-2008. Significant correlations of temperature extremes and elevation in-cluded the trends of diurnal temperature range, frost days, ice days, cold night frequency and cold day frequency. Regional trends of growing season length, warm night frequency, coldest night and warmest night displayed a statistically significant positive correlation with altitude. These characteristics indicated the obvious warming with altitude. For precipitation extreme indices, only the trends of consecutive dry days, consecutive wet days, wet day precipitation and the number of heavy precipitation days had significant correlations with increasing alti-tude owing to the complex influence of atmospheric circulation. It also indicated the increased precipitation mainly at higher altitude areas, whereas the increase of extreme precipitation events mainly at lowers altitude. In addition, the clearly local influences are also crucial on climate extremes. The analysis revealed an enhanced sensitivity of climate extremes to ele-vation in southwestern China in the context of recent warming.     

A modified peak‐bagging technique for fitting low‐𝓁 solar p‐modes

We introduce a modified version of a standard power spectrum ‘peak‐bagging’ technique which is designed to gain some of the advantages that fitting the entire low‐degree p‐mode power spectrum simultaneously would bring, but without the problems involved in fitting a model incorporating many hundreds of parameters. Employing Monte‐Carlo simulations we show that by using this modified fitting code it is possible to determine the true background level in the vicinity of the p‐mode peaks. In addition to this we show how small biases in other mode parameters, which are related to inaccurate estimates of the true background, are also consequently removed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nature and significance of the Neoproterozoic Sturtian–Marinoan Boundary,Northern Adelaide Geosyncline,South Australia

The Cryogenian succession of the Northern Flinders Ranges reveals a complex sedimentary record between the Sturtian and Marinoan glacial deposits. A major unconformity separates the Sturtian and Marinoan-aged sedimentary successions in the area. This forms a subaerial erosion surface with terrestrial and marginal marine infill directly above the Angepena and Balcanoona Formations in their respective localities. This exposure surface is here correlated with the previously documented submarine unconformity between the Yankaninna Formation and the underlying deep marine Tapley Hill Formation. This erosional event provides a chronostratigraphic marker horizon that coincides approximately with thepreviously defined Sturtian–Marinoan Time Series boundary in the Northern Flinders Ranges. These stratigraphic relationships also constrain lateral facies relationships between the Oodnaminta ReefComplex (Balcanoona Formation) and the Angepena Formation. Similarly, the shallow-water Weetootla Dolomite is correlated with the deeper water carbonates of the Yankaninna Formation.     

Development of the auroral absorption substorm: Studies of pre-onset phase and sharp onset using an extensive riometer network

The development of an auroral absorption substorm has been studied using riometer measurements in the northern hemisphere. In the events studied, the onset is preceded by an absorption bay which begins to develop $\text{1?1}\text{1}\text{2}\text{h}$ before the onset. The bay may occur between L-values 3–19 and can cover as much as 150° of geomagnetic longitude, generally in the same longitudinal sector where the substorm breaks up and to the west of it. Whereas the substorm breaks up at or near the midnight meridian, the preceding bay may, in some geophysical conditions, appear in the afternoon sector. The preceding bay moves southward with a velocity between 60 and 600 ms^?1, intensifying during the movement. This equatorward movement is consistent with an E × B drift in a cross-magnetotail electric field of between 0.5 and 1 mV m^?1. The absorption at the onset exceeds that in the bay, and in the sector of break up the absorption shows a minimum just before the onset; to the west-of the break up the preceding bay continues its southward movement. In 14 cases studied, the sharp onset moved to the west with a velocity of 1–31 km s^?1, median 6 km s^?1. The onset was seen at higher L-values to the west than in the break-up sector. This applied also to the preceding bay. Whereas most onsets showed westward movement, in only about half of the cases studied was there movement towards the east. The injection area affected during the first minute of the onset was typically 1–2 L-value units, but as much as 30° of geomagnetic longitude. The onset later spread to cover 1–10 L-value units, and up to 130° of longitude. The contouring method used in the analysis of the data from the riometer is described in the Appendix.