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Bi-Qing For Elizabeth M. Green Gilles Fontaine Scott Shaw 《Astrophysics and Space Science》2010,328(1-2):87-90
In this paper, we report a rare reflection effect eclipsing sdB+dM binary, 2M?1533+3759. It is the seventh eclipsing sdB+dM binary that has been discovered to date. This system has an orbital period of 0.16177042 day and a velocity semi-amplitude of 71.1 km?s?1. Using a grid of zero-metallicity NLTE model atmospheres, we derived T eff=29250 K, log?g=5.58 and [He/H]=?2.37 from spectra taken near the reflection effection minimum. Lightcurve modeling resulted in a system mass ratio of 0.301 and an orbital inclination angle of 86.6°. The derived primary mass for 2M?1533+3759, 0.376±0.055 M ⊙, is significantly lower than the canonical mass (0.48 M ⊙) found for most previously investigated sdB stars. This implies an initial progenitor mass >1.8 M ⊙, at least a main sequence A star and perhaps even one massive enough to undergo non-degenerate helium ignition. 相似文献
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P. Hily-Blant E. Falgarone G. Pineau des Forêts T. G. Phillips 《Astrophysics and Space Science》2004,292(1-4):285-289
We present a multitransition study in the 13CO(1-0), 12CO(2-1), 12CO(3-2) and 12CO(4-3) lines of a parsec scale elongated structure connected to a low-mass dense core. Densities larger than n H 2 = 104 cm?3 are inferred in the central regions of this structure, supporting the proposition that it is a genuine filament denser than its environment. The sharp observed drop of the 12CO and 13CO emissions requires a power law density fall-off steeper than r ?1 although a single density law cannot reproduce the spatial shift of 0.1 pc between the 13CO and 12CO drops. Our results support the previous proposition that this elongated structure is a filament threaded by helical magnetic fields, channeling the gas inflow onto the dense core. 相似文献
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据ＫＣｌ含量的概率分布特征,晶间卤水分为７个总体。晶间卤水ＫＣｌ,在三级系统内水平分异有２种、剖面分异有５种,二级系统内水平分异呈环带状、剖面分异形式为三级系统内分异形式的组合,垂直分异有１３种;富集的总体为Ⅳ（ｋｃｌ）、Ⅲ（ｋｃｌ）用Ｖ（ｋｃｌ）、三级系统为（８）和（１０）号、部位为固相钾高含处;分异及富集的成因主要为晶间卤水的阶段性淡化。 相似文献
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Research Group For Explosion Seismology 《Tectonophysics》1973,20(1-4):129-132
Crustal structures of Japan were investigated under the Upper Mantle Project in three profiles, Kurayosi-Hanabusa, western Japan; Atumi-Noto, central Japan; Kesennuma-Oga, northeastern Japan. These investigations have revealed that the crust of Japan is of continental type. The variation of the crustal structure reflects the topography, especially the water depth; so the thinning of the crust occurs near the shore where the water depth increases rapidly. The velocity below the Mohorovi?i? discontinuity is smaller than 8.0 km/sec, but it is possible that a deeper layer with a velocity of over 8.0 km/sec may exist. The basaltic layer in central Japan, if existing at all, must be thin. 相似文献
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Suzanna Randall Gilles Fontaine Elizabeth Green Dave Kilkenny Lisa Crause Oliver Cordes Simon O’Toole Lázló Kiss Bi-Qing For Pierre-Olivier Quirion 《Astrophysics and Space Science》2004,291(3-4):465-471
We report on the outcome of the first major multi-site campaign on a long-period variable subdwarf B star. The target PG 1627+017 was observed for a total of 334 h during April/May/June 2003 from the lynchpin observatory at Mt. Bigelow, Arizona, with important contributions coming from co-observations at SAAO, Calar Alto and Siding Spring. Preliminary analysis indicates the presence of 8–10 probable periods in the range ～4500 to ～8900 s with relative amplitudes between 0.1 and 0.5%;. The range over which the periods are found is in qualitative agreement with theoretical predictions and the number of periods found shows potential for an in-depth asteroseismological analysis. Multi-colour observations show that the relative amplitudes of pulsation are larger in the U-band than in the R, which again is in agreement with theory. However, more multi-colour observations are needed to be able to make statements at the quantitative level. 相似文献
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Paul T.ROBINSON 《《地质学报》英文版》2001,75(1):41-50
The Aoyougou ophiolite lies in an early Palaeozoic orogenic belt of the western North Qilian Mountains, near the Aoyougou valley in Gansu Province, northwestern China. It consists of serpentinite, a cumulate sequence of gabbro and diorite, pillow and massive lavas, diabase and chert. Ages of 1840±2 Ma, 1783±2 Ma and 1784±2 Ma on three zircons from diabase, indicate an early Middle Proterozoic age. The diabases and basalts show light rare-earth element enrichment and have relatively high TiO2 contents, characteristic of ocean island basalts. All of the lavas have low MgO, Cr, Ni contents and Mg numbers indicating a more evolved character. They are believed to have been derived from a more mafic parental magma by fractionation of olivine, Cr-spinel and minor plagioclase. Based on the lava geochemistry and regional geology, the Aoyougou ophiolite was probably believed to have formed at a spreading centre in a small marginal basin. Subduction of the newly formed oceanic lithosphere in the Middle Proteroz 相似文献
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D.R. Flower J. Le Bourlot G. Pineau des Forêts S. Cabrit 《Astrophysics and Space Science》2003,287(1-4):183-186
The shock waves associated with molecular outflows may be of continuous (C) type or jump (J) type, depending on conditions in the preshock gas, notably the degree of ionization. Intermediate situations also exist, in which a J-discontinuity terminates or is embedded in a C-type flow. We consider the results of recent modelling of several important cases where shock waves will comprise both C and J components, namely: (1) in the evolution of a planar J into a planar C type shock wave, prior to the attainment of a stationary state; (2) at shock speeds exceeding the maximum value for a planar C type shock, when the cooling flow encounters a sonic point; (3) in a curved bowshock, when the shock speed at the apex exceeds the maximum value for a C type shock while the bow wings remain of C type. We show that proper allowance for the departure of the chemistry from equilibrium, particularly the dissociation/reformation of H2, is crucial for an accurate treatment of the C to J transition. All the possible modes of shock propagation need to be considered when interpreting observations of molecular outflow sources. An important diagnostic tool in this context is the H2 excitation diagram, which plots the logarithm of the column densities of the H2 rotational levels, divided by the statistical weights, against their excitation energies. There can be large differences between the dynamical and physical conditions implied by J type shocks (with and without a precursor), C type shocks, and bowshocks which best fit the observed excitation diagram. We discuss, by means of examples, the use of the excitation diagram, in conjunction with our sophisticated shock model, to constrain conditions in shocks propagating in molecular outflows. 相似文献
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S. Cabrit D.R. Flower G. Pineau des Forêts J. Le Bourlot C. Ceccarelli 《Astrophysics and Space Science》2004,292(1-4):501-508
The shock waves associated with molecular outflows may be of continuous (C) type or jump (J) type, depending on conditions in the preshock gas, notably the magnetic field strength and the degree of ionisation. Intermediate situations also exist, in which a J-discontinuity terminates or is embedded in a C-type flow. We show that proper allowance for the departure of the chemistry from equilibrium (particularly the dissociation/reformation of H2) and for the inertia of charged dust grains, is crucial for an accurate treatment of the C to J transition. We illustrate the use of H2 population diagrams and H2 line profiles, in conjunction with our detailed shock model, to constrain conditions in shocks propagating in molecular outflows. We show that H2 pure rotational lines yield evidence for C-type precursors in bipolar outflows from young stars, with transverse magnetic field strengths B (μG) ? 1–10 × $\sqrt {n_{H/{\text{cm}}^{ - 3} } } $ similar to those inferred from Zeeman splitting and from the dispersion of dust polarization vectors in dense clouds. 相似文献