Modelling interaction of relativistic and non-relativistic winds in binary system PSR B1259−63/SS2883 – I. Hydrodynamical limit     

S. V. Bogovalov  D. V. Khangulyan  A. V. Koldoba  G. V. Ustyugova  F. A. Aharonian 《Monthly notices of the Royal Astronomical Society》2008,387(1):63-72

In this paper, we present a detailed hydrodynamical study of the properties of the flow produced by the collision of a pulsar wind with the surrounding in a binary system. This work is the first attempt to simulate interaction of the ultrarelativistic flow (pulsar wind) with the non-relativistic stellar wind. Obtained results show that the wind collision could result in the formation of an 'unclosed' (at spatial scales comparable to the binary system size) pulsar wind termination shock even when the stellar wind ram pressure exceeds significantly the pulsar wind kinetic pressure. Moreover, the post-shock flow propagates in a rather narrow region, with very high bulk Lorentz factor (γ∼ 100). This flow acceleration is related to adiabatic losses which are purely hydrodynamical effects. Interestingly, in this particular case, no magnetic field is required for formation of the ultrarelativistic bulk outflow. The obtained results provide a new interpretation for the orbital variability of radio, X-ray and gamma-ray signals detected from binary pulsar system PSR B1259−63/SS2883.  相似文献   

Interstellar holography     

M. A. Walker  L. V. E. Koopmans  D. R. Stinebring  W. van Straten 《Monthly notices of the Royal Astronomical Society》2008,388(3):1214-1222

The dynamic spectrum of a radio pulsar is an in-line digital hologram of the ionized interstellar medium. It has previously been demonstrated that such holograms permit image reconstruction, in the sense that one can determine an approximation to the complex electric field values as a function of Doppler shift and delay, but to date the quality of the reconstructions has been poor. Here we report a substantial improvement in the method which we have achieved by simultaneous optimization of the thousands of coefficients that describe the electric field. For our test spectrum of PSR B0834+06 we find that the model provides an accurate representation of the data over the full 63 dB dynamic range of the observations: residual differences between model and data are noise like. The advent of interstellar holography enables detailed quantitative investigation of the interstellar radio-wave propagation paths for a given pulsar at each epoch of observation. We illustrate this using our test data which show the scattering material to be structured and highly anisotropic. The temporal response of the medium exhibits a scattering tail which extends to beyond  100 μs  , and the centroid of the pulse at this frequency and this epoch of observation is delayed by approximately  15 μs  as a result of multipath propagation in the interstellar medium.  相似文献   

模拟水氡仪与数字化水氡仪对比观测实验   总被引：1，自引：0，他引：1  

姚玉霞  ;杨晓鹏  ;陈兰庆  ;杨斐  ;李松林  ;史继平 《地震地磁观测与研究》2014,(3):182-186

在相同观测条件下,选用平凉地震台北山2号泉水样作为实验目标,用 FD-125型模拟水氡仪与 SD-3B 型数字水氡仪进行对比观测实验;搜集全国用相同方法观测的5个地震台的观测资料进行对比分析,结果表明：FD-125型模拟水氡仪性能明显优于 SD-3B 型数字水氡仪。  相似文献   

The Forming Conditions of and Ore- searching Direction for B, Mg, Pb, Zn and Au Deposits in the Liaoji Proterozoic Rift     

Zhu Yongzheng  Yao Fengliang 《世界地质(英文版)》2001,4(1)

The Liaoji Proterozoic rift is an inter- intracontinenatl rift developed from Archean granite- greenstone tectonic regime and contains many important mineral deposits of U, B, magnesite, Pb - Zn, Au, Ag, Co and P. These deposits were formed as the result of late mobilization, transportation and concentration of the previously enriched ore - forming materials in several ore- bearing formations formed during the rift stage. So the metallogeny of these deposits in the rift shows both inheritance and new generation of the ore - forming materials. In future ore - searching practice, attentions should be paid on the studies of the ore - bearing formations in the rift, on the multiple stages of metallogeny and and on multiple derivations of the ore - forming materials.  相似文献   

Keck spectroscopy of Cosmic Lens All-Sky Survey gravitational lenses     

J. P. McKean  L. V. E. Koopmans  I. W. A. Browne  C. D. Fassnacht  R. D. Blandford  L. M. Lubin  A. C. S. Readhead 《Monthly notices of the Royal Astronomical Society》2004,350(1):167-174

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Dense cores in the L1630 molecular cloud: discovering new protostars with SCUBA     

Robin R. Phillips †  y G. Gibb ‡  Leslie T. Little 《Monthly notices of the Royal Astronomical Society》2001,326(3):927-936

Maps of the 450- and 850-μm dust continuum emission from three star-forming condensations within the Lynds 1630 molecular cloud, made with the SCUBA bolometer array, reveal the presence of four new submillimetre sources, each of a few solar masses (two of which are probably class I and two of which are class 0), as well as several sources the existence of which was previously known. The sources are located in filaments and appear elongated when observed at 450 μm. They probably have dust temperatures in the range 10 to 20 K, in good agreement with previous ammonia temperature estimates. Attempts to fit their structures with power-law and Gaussian density distributions suggest that the central distribution is flatter than expected for a simple singular isothermal sphere.
Although the statistics are poor, our results suggest that the ratio of 'protostellar core' mass to total virial mass may be similar for both large and small condensations.  相似文献   

B2114+022: a distant radio source gravitationally lensed by a starburst galaxy     

Pedro Augusto †  Ian W. A. Browne  Peter N. Wilkinson  Neal J. Jackson  Chris D. Fassnacht ‡  Tom W. B. Muxlow  Jens Hjorth  reas O. Jaunsen  Leon V. Koopmans  Alok R. Patnaik  Greg B. Taylor 《Monthly notices of the Royal Astronomical Society》2001,326(3):1007-1014

We have discovered a radio source (B2114+022) with a unique structure during the course of the JVAS gravitational lens survey. VLA, MERLIN, VLBA and MERLIN+EVN radio maps reveal four compact components, in a configuration unlike that of any known lens system, or, for that matter, any of the ∼15 000 radio sources in the JVAS and CLASS surveys. Three of the components are within 0.3 arcsec of each other while the fourth is separated from the group by 2.4 arcsec. The widest separation pair of components have similar radio structures and spectra. The other pair also have similar properties. This latter pair have spectra which peak at ∼5 GHz. Their surface brightnesses are much lower than expected for synchrotron self-absorbed components.
Ground-based and Hubble Space Telescope optical observations show two galaxies ( z =0.3157 and 0.5883) separated by 1.25 arcsec. The lower redshift galaxy has a post-starburst spectrum and lies close to, but not coincident with, the compact group of three radio components. No optical or infrared emission is detected from any of the radio components down to I =25 and H =23 . We argue that the most likely explanation of the B2114+022 system is that the post-starburst galaxy, assisted by the second galaxy, lenses a distant radio source producing the two wide-separation images. The other two radio components are then associated with the post-starburst galaxy. The combination of the angular sizes of these components, their radio spectra and their location with respect to their host galaxy still remains puzzling.  相似文献   

Reconsidering Melt-water Pulses 1A and 1B： Global Impacts of Rapid Sea-level Rise   总被引：2，自引：0，他引：2  

J.PaulLiu JohnD.Milliman 《中国海洋大学学报(英文版)》2004,3(2):183-190

Re-evaluation of the post-glacial sea level derived from the Barbados coral-reef borings suggests slightly revised depth ranges and timing of melt-water pulses MWP-1A (96-76m, 14.3-14.0ka cal BP) and 1B (58-45 m, 11.5-11.2ka cal BP), respectively. Ages of non-reef sea-level indicators from the Sunda Shelf, the East China Sea and Yellow Sea for these two intervals are unreliable because of the well-documented radiocarbon (^14C) plateau, but their vertical clustering corresponds closely with MWP-1A and 1B depth ranges. Close correlation of the revised sea-level curve with Greenland ice-core data suggests that the ^14C plateau may be related to oceanographic-atmospheric changes due to rapid sea-level rise, fresh-water input, and impaired ocean circulation. MWP-1A appears to have occurred at the end of Bφlling Warm Transition, suggesting that the rapid sea-level rise may have resulted from lateral heat transport from low to high-latitude regions and subsequent abrupt ice-sheet collapses in both North America-Europe and Antarctica. An around 70 mma^-1 transgression during MWP-1A may have increased freshwater discharge to the North Atlantic by as much as an order of magnitude, thereby disturbing thermohaline circulation and initiating the Older Dryas global cooling.  相似文献   

黄土-古土壤沉积物中酸溶相硼的分离及其同位素测定   总被引：5，自引：0，他引：5  

赵志琦  刘丛强  肖应凯 《地球化学》2000,29(4):351-357

用０．５ｍｏｌ／ＬＨＣｌ提取黄土、古土壤中的酸溶相成分,并用混合树脂法和硼特效树脂法两方法叠加以硼进行分离和纯化,Ｃｓ２ＢＯ２＾＋法测同位素比值。结果表明,虽然混合树脂法和硼特效脂法都是较成熟的方法,但用来处理杂质离子含量相对高而硼含量低的样品深液并不成功。两种方法叠加处理后达到理想的效果,重复处理黄土－古土壤样品的精度（２ＲＳＤ）在０．４‰～０．４‰之间,这与标样（ＮＩＳＴ ＳＲＭ９５１）水平（  相似文献   

Models for the lens and source of B0218+357: a LensClean approach to determine H₀     

O. Wucknitz  A. D. Biggs  I. W. A. Browne 《Monthly notices of the Royal Astronomical Society》2004,349(1):14-30

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