Luminosity function of contact binaries based on the All Sky Automated Survey (ASAS)

The luminosity function for contact binary stars of the W UMa type is evaluated on the basis of the All Sky Automated Survey (ASAS) photometric project covering all stars south of  δ=+ 28°  within a magnitude range  8 < V < 13  . Lack of colour indices enforced a limitation to 3374 systems with   P < 0.562 d  (i.e. 73 per cent of all systems with   P < 1 d  ) where a simplified M_V (log  P ) calibration could be used. The spatial density relative to the main-sequence FGK stars of 0.2 per cent, as established previously from the Hipparcos sample to   V = 7.5  , is confirmed. While the numbers of contact binaries in the ASAS are large and thus the statistical uncertainties small, derivation of the luminosity function required a correction for missed systems with small amplitudes and with orbital periods longer than 0.562 d; the correction, by a factor of 3, carries an uncertainty of about 30 per cent.     

Comparison between polar regions of Mars from HEND/Odyssey data

In this paper, we have analyzed neutron spectroscopy data gathered by the High Energy Neutron Detector (HEND) instrument onboard Mars Odyssey for comparison of polar regions. It is known that observation of the neutron albedo of Mars provides important information about the distribution of water-ice in subsurface layers and about peculiarities of the CO₂ seasonal cycle. It was found that there are large water-rich permafrost areas with contents of up to ∼50% water by mass fraction at both the north and south Mars polar regions. The water-ice layers at high northern latitudes are placed close to the surface, but in the south they are covered by a dry and relatively thick (10-20 cm) layer of soil. Analysis of temporal variations of neutron flux between summer and winter seasons allowed the estimation of the masses of the CO₂ deposits which seasonally condense at the polar regions. The total mass of the southern seasonal deposition was estimated as 6.3×¹⁰¹⁵ kg, which is larger than the total mass of the seasonal deposition at the north by 40-50%. These results are in good agreement with predictions from the NASA Ames Research Center General Circulation Model (GCM). But, the dynamics of the condensation and sublimation processes are not quite as consistent with these models: the peak accumulation of the condensed mass of CO₂ occurred 10-15 degrees of Ls later than is predicted by the GCM.     

On the self-consistency of evolutionary synthesis models

Evolutionary synthesis models have been used to study the physical properties of unresolved populations in a wide range of scenarios. Unfortunately, their self-consistency is difficult to test and there are some theoretical open questions without an answer: (1) The change of the homology relations assumed in the computation of isochrones due to the effect of stellar winds (or rotation) and the discontinuities in the stellar evolution are not considered. (2) There is no consensus about how the isochrones must be integrated. (3) The discreteness of the stellar populations (that produce an intrinsic statistical dispersion) usually are not taken into account, and model results are interpreted in a deterministic way instead of a statistical one. The objective of this contribution is to present some inconsistencies in the computation and some cautions in the application of the results of such codes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Deep Processes of Basin Evolution:A Case Study of the Southern Songliao Basin and Adjacent Area,NE China in Mesozoic-Cenozoic

1IntroductionOne of the key factors related to basin geody-namics is deep process controlling formation and evolution of sedimentary basin. Depth and tempera-ture of asthenosphere,existence of mantle plume,occurrence of mantle melting,and amounts of melts under depressurization during thinning of lithosphere are controlling factors influenced formation and characteristics of extensional basin directly (Li,1994). Rifting is probably governed by frictional forces exerted on the base of litho…     

Tests and constraints on theories of galaxy formation and evolution

Tests and constraints on current theories of galaxy formation and evolution are presented. They are derived from observations of the Northern Hubble Deep Field with WFPC2 and NICMOS. Photometric redshifts, extinctions and spectral energy distributions are calculated for all objects in the field. The tests and constraints are derived from the output of this analysis. The tests of the predictions from hierarchical and pure luminosity evolution galaxy evolution calculations favor the hierarchical model. Constraints are provided by the current luminosity function and its evolution to a redshift of 6. This revised version was published online in August 2006 with corrections to the Cover Date.     

North European last glacial–interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events

High‐precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change. Although radiocarbon is the traditional method for dating late Quaternary sedimentary sequences, particularly during the last glacial–interglacial transition (LGIT; 15–9 ka), there are inherent problems with the method, particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content. An alternative method is the use of tephras that act as time‐parallel marker horizons. Within Europe, numerous volcanic centres are known to have erupted during the LGIT, providing considerable potential for high‐precision correlation independent of past radiocarbon fluctuations. Here we report the first identification of the Vedde Ash and Askja Tephra in Ireland, significantly extending the known provenance of these events. We have also identified two new horizons (the Roddans Port Tephras A and B) and tentatively recognise an additional horizon from Vallensgård Mose (Denmark) that provide crucial additional chronological control for the LGIT. Two phases of the Laacher See Tephra (LST) are reported, the lower Laacher See Tephra (LLST) and probably the C2 phase of the Middle Laacher See Tephra (MLST‐C2) indicating a more northeasterly distribution of this fan than reported previously. Copyright © 2006 John Wiley & Sons, Ltd.