SWIFT J1749.4-2807: A neutron or quark star?     

Jun-Wei Yu  Ren-Xin Xu 《中国天文和天体物理学报》2010,10(9)

We investigate a unique accreting millisecond pulsar with X-ray eclipses,SWIFT J1749.4-2807(hereafter J1749),and try to set limits on the binary system by various methods including use of the Roche lobe,the mass-radius relations of both main sequence(MS)and white dwarf(WD)companion stars,as well as the measured mass function of the pulsar.The calculations are based on the assumption that the radius of the companion star has reached its Roche radius(or is at 90%),but the pulsar's mass has not been assumed to be a certain value.Our results are as follows.The companion star should be an MS one.For the case that the radius equals its Roche one,we have a companion star with mass M(～-)0.51 M⊙ and radius Rc(～-)0.52 R⊙,and the inclination angle is i(～-)76.5°; for the case that the radius reaches 90% of its Roche one,we have M(～-)0.43 M⊙,Re()0.44 R⊙ and i(～-)75.7°.We also obtain the mass of J1749,Mp(～-)1 M⊙,and conclude that the pulsar could be a quark star if the ratio of the critical frequency of rotation-mode instability to the Keplerian one is higher than～0.3.The relatively low pulsar mass(about～M⊙)may also challenge the conventional recycling scenario for the origin and evolution of millisecond pulsars.The results presented in this paper are expected to be tested by future observations.  相似文献   

Several fourth-order force gradient symplectic algorithms     

Jia Xu  Xin Wu 《中国天文和天体物理学报》2010,10(2)

By adding force gradient operators to symmetric compositions, we build a set of explicit fourth-order force gradient symplectic algorithms, including those of Chin and coworkers, for a separable Hamiltonian system with quadratic kinetic energy T and potential energy V . They are extended to solve a gravitational n-body Hamiltonian system that can be split into a Keplerian part H 0 and a perturbation part H 1 in Jacobi coordinates. It is found that the accuracy of each gradient scheme is greatly superior to ...  相似文献   

GRB jet beaming angle statistics     

Yan Gao  Zi-Gao Dai 《中国天文和天体物理学报》2010,10(2)

Existing theory and models suggest that a Type I (merger) GRB should have a larger jet beaming angle than a Type II (collapsar) GRB, but so far no statistical evidence is available to support this suggestion. In this paper, we obtain a sample of 37 beaming angles and calculate the probability that this is true. A correction is also devised to account for the scarcity of Type I GRBs in our sample. The probability is calculated to be 83% without the correction and 71% with it.  相似文献   

Nonlinear adaptive observer-based sliding mode control for LAMOST mount driving     

Wang-Ping Zhou  Yi Zheng  Wei Guo  Li Yu  Chang-Song Yang School of Information & Control Engineering  Nanjing University of Information Science & Technology  Nanjing  China  Nanjing Institute of Astronomical Optics & Technology  National Astronomical Observatories  Chinese Academy of Sciences  Nanjing 《中国天文和天体物理学报》2010,10(1)

Heavy disturbances caused mainly by wind and friction in the mount drive system greatly impair the pointing accuracy of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST).To overcome this negative effect,a third order Higher Order Sliding Mode (HOSM) controller is proposed.The key part of this approach is to design an appropriate observer which obtains the acceleration state.A nonlinear adaptive observer is proposed in which a novel polynomial model is applied to estimate the internal di...  相似文献   

Debris disks: seeing dust, thinking of planetesimals and planets     

Alexander V. Krivov 《中国天文和天体物理学报》2010,10(5)

Debris disks are optically thin, almost gas-free dusty disks observed arounda significant fraction of main-sequence stars older than about 10 Myr. Since the circumstellar dust is short-lived, the very existence of these disks is considered as evi-dence that dust-producing planetesimals are still present in mature systems, in whichplanets have formed – or failed to form – a long time ago. It is inferred that theseplanetesimals orbit their host stars at asteroid to Kuiper-belt distances and continuallysupply ...  相似文献   

Aggregate dust model to study the polarization properties of comet C/1996 B2 Hyakutake     

Himadri Sekhar Das  Abinash Suklabaidya  Saonli Datta Majumder  Asoke Kumar Sen 《中国天文和天体物理学报》2010,10(4)

The observed linear polarization data of comet Hyakutake are studied at wavelengths λ=0.365 μm,λ=0.485 μm and 0.684 μm through simulations using Ballistic Particle-Cluster Aggregate and Ballistic Cluster-Cluster Aggregate aggregates of 128 spherical monomers.We first found that the size parameter of the monomer,x～1.56-1.70,turned out to be the most suitable which provides the best fits to the observed dust scattering properties at three wavelengths:λ=0.365 μm,0.485 μm and 0.684 μm.Thus,the effective radius of the aggregate(r)lies in the range 0.45 μm ≤ r≤ 0.49 μm at λ=0.365 μm;0.60μm < r < 0.66 μm at λ=0.485 μmand 0.88 μm < r < 0.94 μm at λ=0.684 μm.Now using superposition T-MATRIX code and the power-law size distribution,n(r)～r-3,the best-fitting values of complex refractive indices are calculated for the observed polarization data at the above three wavelengths.The best-fitting complex refractive indices(n,k)are found to be (1.745,0.095)at λ=0.365 μm,(1.743,0.100)at λ=0.485 μm and(1.695,0.100)at λ=0.684 μm.The refractive indices derived from the present analysis correspond to a mixture of both silicates and organics,which are in good agreement with the in situ measurement of comets by different spacecraft.  相似文献   

绿色技术创新能否提高能源利用效率——以中国沿海地区为例的实证研究          下载免费PDF全文

翟仁祥  石哲羽 《海洋开发与管理》2022,39(4):43-49

为促进我国的节能减排以及经济高质量发展,文章分析我国沿海地区绿色技术创新与能源利用效率的关系,并通过中介变量分析二者之间的内在传导机制,在此基础上提出对策建议。研究结果表明：绿色技术创新能够提高能源利用效率,但二者之间存在门槛效应,当越过门槛值时绿色技术创新对能源利用效率的提高作用有所减弱;产业结构、城市化水平和信息化水平是绿色技术创新提高能源利用效率的中介传导因素;未来我国应进一步完善生态文明顶层设计、优化产业结构和布局、合理控制城镇和人口规模以及以信息化带动工业化发展。  相似文献   

OJ 287的引力波辐射研究     

孙玉涛  刘杰英  刘进忠  艾艳丽  周明  乔二林 《天文学报》2010,51(4)

类星体OJ 287的研究已经有100多年的历史,它呈现周期性双峰爆发现象,爆发周期为12 yr,比较好地解释观测的模型是双黑洞模型,即次黑洞绕主黑洞运动,并撞击主黑洞吸积盘从而引起爆发.此模型合理地解释了OJ 287的光变曲线并正确预言了未来爆发时间,这间接证明了广义相对论进动效应以及引力波的存在.星系中心大质量黑洞是一类重要的引力波源,而精确确定了其内部组分运动学方程的星系非常少,由于双黑洞模型提供了精确的黑洞运动轨道,故可以在这个运动轨道基础上研究其引力波辐射.在已有工作基础上,采用后牛顿近似方法首次得到了引力波辐射功率和波形随时间的演化关系,根据目前引力波探测设备IPTA(International Pulsar Timing Array)的进展情况,未来十几年内对OJ 287的引力波直接探测将成为可能.  相似文献   

不同仪器GRB观测数据的一致性分析     

林一清 《天文学报》2010,51(4)

BATSE(Compton Gamma-Ray Observatory/Bursts and Transient SourceExperiment)、Swift(Swift Gamma-ray Burst Explorer)和Fermi卫星(Fermi GammaraySpace Telescope)提供了大量的GRB样本.研究比较3种仪器观测的暴的特征,发现虽然有红移暴的数目、所有暴中长暴的比例以及光子流量分布(lgN-lgP分布)等有显著差异,但是暴的持续时间、伽玛辐射总流量、谱硬度比等均没有显著差异.考虑Swift和Fermi暴的观测能段不同,进行修正以后,发现lgN-lgP分布的差异也基本消除.有红移暴的数目、长暴占总暴数的比例是由仪器本身的灵敏度决定的,即不同仪器决定不同GRB的观测特征,但是它们的本质是一致的.  相似文献   

环火卫星运动的坐标系附加摄动及相应坐标系的选择   总被引：1，自引：0，他引：1  

刘林  赵玉晖  张巍  王彦荣  王家松 《天文学报》2010,51(4)

与处理地球卫星相关问题类似,在研究和处理环火卫星(尤其是低轨卫星)的轨道问题时,宜采用火心历元平赤道坐标系,即火心天球坐标系,其xy坐标面和x轴方向就是相应的平赤道面和平春分点方向.与地球的岁差章动现象类似,在该坐标系中,火星赤道面在空间的摆动同样会引起坐标系附加摄动.采用类似对地球岁差章动的处理方法,在一定精度前提下,基于IAU2000火星定向模型,处理了火星赤道面摆动中的岁差效应,并在此基础上,研究岁差对环火卫星轨道的影响,给出了相应的火星非球形引力位的变化及其导致的卫星轨道的坐标系附加摄动解,其表达形式简单,引用方便.与高精度数值解的比对表明,该分析解能够满足通常的精度要求.因此,在处理环火卫星(即使是低轨卫星)轨道及其相关问题时,可以采用统一坐标系:火心天球坐标系.而不必像当初处理地球卫星那样,为了避免计算坐标系附加摄动而引进一种混合型赤道坐标系,即采用瞬时真赤道面和历元平春分点方向作为其xy坐标面和x轴方向.在统一坐标系的选择下,实际工作中就不会存在坐标系转换的麻烦.  相似文献