Modelling Gas And Dust Release From Comet Hale–Bopp     

Prialnik  D. 《Earth, Moon, and Planets》1997,77(3):223-230

Numerical simulations of the evolving activity of comet Hale-Bopp are presented, assuming a porous, spherical nucleus, 20 km in radius, made of dust and gas-laden amorphous ice. The main effects included are: crystallization of amorphous ice and release of occluded gas, condensation, sublimation and flow of gases through the pores, changing pore sizes, and flow of dust grains. The model parameters, such as initial pore size and porosity, emissivity, dust grain size, are varied in order to match the observed activity. In all cases, a sharp rise in the activity of the nucleus occurs at a large heliocentric distance pre-perihelion, marked by a few orders of magnitude increase in the CO and the CO₂ fluxes and in the rate of dust emission. This is due to the onset of crystallization, advancing down to a few meters below the surface, accompanied by release of the trapped gases. A period of sustained, but variable, activity ensues. The emission of water molecules is found to surpass that of CO at a heliocentric distance of 3 AU. Thereafter the activity is largely determined by the behaviour of the dust. If a dust mantle is allowed to build up, the water production rate does not increase dramatically towards perihelion; if most of the dust is ejected, the surface activity increases rapidly, producing a very bright comet. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Relativist ic Corrections to the Thermal Sunyaev-Zel''''dovich Power Spectrum     

Hai-Ning LiNational Astronomical Observatories  Chinese Academy of Sciences  Beijing  lhnDepartment of Astronomy  Beijing Normal University  Beijing 《中国天文和天体物理学报》2003,3(5)

We present a quantitative estimate of the relativistic corrections to the thermal SZ power spectrum produced by the energetic electrons in massive clusters. The corrections are well within 10% for current experiments with working frequencies below v < 100 GHz, but become non-negligible at high frequencies v > 350 GHz. Moreover, the corrections appear to be slightly smaller at higher l or smaller angular scales. We conclude that there is no need to include the relativistic corrections in the theoretical study of the SZ power spectrum especially at low frequencies unless the SZ power spectrum is used for precision cosmology.  相似文献   

基于J2EE架构的企业卡资源管理系统的设计与实现     

任建豪  李成忠 《成都信息工程学院学报》2005,20(5):566-570

介绍了J2EE架构和多层体系结构的发展，在B／S三层架构的基础上给出了包含应用服务器中间件的多层分布式应用体系结构，并把此体系结构应用于电信氽业的有价卡管理系统项目中。分析了此项同的功能结构和体系结构，采用J2EE开发平台和技术设计实现了由浏览器、Web服务器、应用服务器、数据库服务器组成的多层体系架构。  相似文献   

利用Lageos 1 SLR资料解算1990-2001年的地球定向参数     

ZHU Yuanlan FENG Chugang ZHOU Yonghong 《中国科学院上海天文台年刊》2003,(1)

利用 12年的Lageos 1卫星激光测距资料 (1990 - 2 0 0 1)解算得到了地球定向参数 (EOP) ,将该序列的结果与同期的EOP(IERS)C0 4进行比较 ,其外符精度为 :极移XP— 0 .4 0mas,YP— 0 .4 2mas ,日长变化Dr— 0 .0 35ms。  相似文献   

A Time Evolution Study of the Superhumps of the Dwarf Nova 1RXS J232953.9+062814 by Wavelet Transform     

Ai-Ying Zhou  Yu-Lei Qiu 《Astrophysics and Space Science》2003,288(3):327-339

The time evolution behaviour of the superhumps of the dwarf nova1RXS J232953.9+ 062814 is investigated with the wavelet analysis method. On the basis of two nights CCD photometry performed during its first superoutburst as well as other published brightness data, we reveal the superhump's time-dependence as a function of periods and time. Our light curves, which phased in the rapid decay ending portion of the superoutburst and in the dawn of a following normal outburst, are important to help trace the superhump evolution for the star. Both the superhump period and the orbital period of the binary system are detected in the present data. We obtain P _sh=0.0458±0.0002d and P _orb=0.0450±0.0002d. They agree with those existing values. The two periods exchanged their roles during the superhump evolution. The general profile of brightness fading over the outbursts roughly followed an exponential decay law or a form of a five-order polynomial. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Dust-enshrouded super star-clusters     

Marc Sauvage  Stéphanie Plante 《Astrophysics and Space Science》2003,284(2):941-944

With the advent of either sensitive space-born infrared cameras, or their high-resolution ground-based siblings, we are uncovering a new category of star clusters: the dust-enshrouded super-star clusters. These manifest themselves only beyond a few microns, as their shroud of dust is able to block all light emitted by the stars themselves. Here we present our results on the spectacular cluster in SBS 0335-052, a very metal-poor galaxy. We also point to the growing number of galaxy analogs to SBS 0335-052, revealing the possibility that these clusters signal a major mode of star formation in starbursts. We conclude by listing a number of open points these clusters raise, in particular with respect to high-redshift counterparts. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

The radio nebula surrounding the Vela pulsar     

R. Dodson †  D. Lewis  D. McConnell  A. A. Deshpande 《Monthly notices of the Royal Astronomical Society》2003,343(1):116-124

  相似文献   

SDSS J143030.22-001115.1： A Misclassified Narrow-line Seyfert 1 Galaxy with Flat X-ray Spectrum     

Wei-Hao Bian  Quan-Ling Cui  Li-Hua Chao Department of Physics  Institute of Theoretical Physics  Nanjing Normal University  Nanjing Key Laboratory for Particle Astrophysics  Institute of High Energy Physics  Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2006,6(3):281-286

We used multi-component profiles to model the Hβ and [OⅢ]λλ4959,5007 lines of SDSS J143030.22-001115.1, a narrow-line Seyfert 1 galaxy (NLS1) in a sample of 150 NLS1 candidates selected from the Sloan Digital Sky Survey (SDSS), Early Data Release (EDR). After subtracting the Hβ contribution from narrow line regions (NLRs), we found that its full width half maximum (FWHM) of broad Hβ line is nearly 2900km s~(-1) , significantly larger than the customarily adopted criterion of 2000 km s~(-1) . With its weak Fe Ⅱ multiples, we believe that SDSS J143030.22-001115.1 should not be classified as a genuine NLS1. When we calculate the virial black hole masses of NLS1s, we should use the Hβ linewidth after subtracting the NLR component.  相似文献   

The HNCO ring in the Sgr B2 region     

Y.C. Minh  W.M. Irvine   《New Astronomy》2006,11(8):594-599

The large-scale structure associated with the 2′N HNCO peak in Sgr B2 [Minh, Y.C., Haikala, L., Hjalmarson, Å., Irvine, W.M., 1998. ApJ 498, 261 (Paper I)] has been investigated. A ring-like morphology of the HNCO emission has been found; this structure may be colliding with the Principal Cloud of Sgr B2. This “HNCO Ring” appears to be centered at (l,b) = (0.7°,−0.07°), with a radius of 5 pc and a total mass of 1.0 × 10⁵ to 1.6 × 10⁶ M. The expansion velocity of the Ring is estimated to be 30–40 km s⁻¹, which gives an expansion time scale of 1.5 × 10⁵ year. The morphology suggests that collision between the Ring and the Principal Cloud may be triggering the massive star formation in the Sgr B2 cloud sequentially, with the latest star formation taking place at the 2′N position. The chemistry related to HNCO is not certain yet, but if it forms mainly via reaction with the evaporated OCN⁻ from icy grain mantles, the observed enhancement of the HNCO abundance can be understood as resulting from shocks associated with the collision between the Principal Cloud and the expanding HNCO Ring.  相似文献   

差分法周跳探测与修复方法改进     

郑作亚  程宗颐  黄珹 《中国科学院上海天文台年刊》2004,(1)

在目前常用的周跳探测与修复方法基础上 ,提出了首先将观测资料按照观测历元不连续分成若干小弧段 ,然后利用差分法进行周跳探测 ,根据差分后周跳放大的特性判断周跳和野值 ,并确定其位置利用宽带组合和电离层组合的方法解算周跳大小。通过实例验证了其有效性。  相似文献