Characteristics of convection and overshooting in RGB and AGB stars     

Xiang-Jun Lai    Yan Li  National Astronomical Observatories/ Yunnan Observatory  Chinese Academy of Sciences  Kunming  China  Key Laboratory for the Structure  Evolution of Celestial Objects  China Graduate University of Chinese Academy of Sciences  Beijing  China. 《中国天文和天体物理学报》2011,(10)

Based on the turbulent convection model (TCM) of Li & Yang, we have studied the characteristics of turbulent convection in the envelopes of 2 and 5M⊙ stars at the red giant branch and asymptotic giant branch phases. The TCM has been successfully applied over the entire convective envelopes, including the convective unstable zone and the overshooting regions. We find that the convective motions become progressively stronger when the stellar models are located farther up along the Hayashi line. In the convect...  相似文献   

Mutual eclipses of J2 Europa by J1 Io observed at Yunnan Observatory in 2009     

Xi-Liang Zhang  Zhong Liu National Astronomical Observatories/ Yunnan Observatory  Joint Laboratory for Optical Astronomy  Chinese Academy of Sciences  Kunming  China  Graduate University of Chinese Academy of Sciences  Beijing 《中国天文和天体物理学报》2011,(10)

Mutual events between natural satellites include mutual occultation and mutual eclipse. Mutual eclipse is another kind of mutual occultation as viewed from the center of the Sun instead of the Earth. Two mutual eclipses of J2 Europa by J1 Io (2009 Aug. 28 and Sept. 12) were observed at Yunnan Observatory during the PHEMU09 international campaign. We will calculate the astrometric data of these Galilean satellites by analyzing and fitting the light curves we obtained. The limb-darkening was considered during...  相似文献   

Solar sail time-optimal interplanetary transfer trajectory design     

Sheng-Ping Gong  Yun-Feng Gao  Jun-Feng Li School of Aerospace  Tsinghua University  Beijing  China 《中国天文和天体物理学报》2011,(8)

The fuel consumption associated with some interplanetary transfer trajectories using chemical propulsion is not affordable. A solar sail is a method of propulsion that does not consume fuel. Transfer time is one of the most pressing problems of solar sail transfer trajectory design. This paper investigates the time-optimal interplanetary transfer trajectories to a circular orbit of given inclination and radius. The optimal control law is derived from the principle of maximization. An indirect method is used...  相似文献   

A note on the discovery of a 2M_⊙ pulsar     

Xiao-Yu Lai  Ren-Xin Xu School of Physics  State Key Laboratory of Nuclear Physics  Technology  Peking University  Beijing  China 《中国天文和天体物理学报》2011,(6)

It is conventionally thought that the state equation of dense matter softens and thus cannot result in high maximum mass if pulsars are quark stars and that a recently discovered 2M⊙ pulsar (PSR J1614-2230) may make pulsars unlikely to be quark stars. However, this standard point of view would be revisited and updated if quark clustering could occur in cold quark matter because of the strong coupling be- tween quarks at realistic baryon densities in compact stars. It can be argued that the state equation of...  相似文献   

Associations of decimetric type Ⅲ bursts with coronal mass ejections and Hα flares     

Yuan Ma  De-Yu Wang  Jun Lin    Shuo Dai  Xue-Fei Zhang National Astronomical Observatories of China / Yunnan Astronomical Observatory  Chinese Academy of Sciences  Kunming  China Purple Mountain Observatory  Nanjing  China Harvard-Smithsonian Center for Astrophysics  Cambridge  MA  USA 《中国天文和天体物理学报》2010,10(5)

We present a statistical study of decimetric type Ⅲ radio bursts,coronal mass ejections(CMEs),and Hα flares observed in the period from July 2000 to March2005.In total,we investigated 395 decimetric type Ⅲ radio burst events,21% of which showed apparent correlation to CMEs that were associated with Hα flares.We noticed that the Hα flares which were strongly associated with CMEs were gradual events,and82% of them took place before CMEs appeared in the field of view of LASCO C2;that most of the CME-associated radio bursts started in the frequency range around750 MHz with a frequency drifting rate of several hundred MHz s-1,of which both positive and negative ones were recognized; and that the correlation of type Ⅲ radio bursts to CMEs without associated flares is fairly vague,less than 9%.  相似文献   

Infrared spectral evolution of carbon stars     

Pei-Sheng Chen  Xiao-Hong Yang  Hong-Guang Shan National Astronomical Observatories /Yunnan Observatory  Key Laboratory for the Structure  Evolution of Celestial Objects  Chinese Academy of Sciences  Kunming  China 《中国天文和天体物理学报》2010,10(4)

We collected almost all Highly Processed Data Products(HPDP)of ISO SWS01 spectra for the Galactic visual carbon stars,infrared carbon stars,extreme carbon stars and carbon-rich proto-planetary nebulae(PPNs).Those infrared spectra are primarily analyzed and discussed.It is shown that either spectral shapes/peaks,or main molecular/dust features are evidenced to change in the sequence of visual carbon stars,infrared carbon stars,extreme carbon stars and carbon-rich PPNs.Statistically,in this sequence,continua are gradually changed from blue to red and locations of spectral peaks of continua are also gradually changed from short wavelengths to long wavelengths.In addition,in this sequence,intensifies of main molecular/dust features are also gradually changed from prominent in the short wavelengths to prominent in the long wavelengths.Furthermore,from 2MASS and IRAS photometric data,the sequence is also proved.Results in this paper strongly support the previous suggestion for the evolution sequence of carbon-rich objects in our Galaxy,that is the sequence of visual carbon stars→infrared carbon stars→extreme carbon stars→carbon-rich PPNs.  相似文献   

Primordial non-Gaussianity from LAMOST surveys     

Yan Gong    Xin Wang  Zheng Zheng  Xue-Lei Chen    National Astronomical Observatories  Chinese Academy of Sciences  Beijing  China  Graduate University of Chinese Academy of Sciences  Beijing  China Institute for Advanced Study  Einstein Drive  Princeton  NJ  USA Center of High Energy Physics  Peking University  Beijing  China Kavli Institute for Theoretical Physics China  CAS  Beijing 《中国天文和天体物理学报》2010,10(2)

The primordial non-Gaussianity (PNG) in the matter density perturbation is a very powerful probe of the physics of the very early Universe. The local PNG can induce a distinct scale-dependent bias on the large scale structure distribution of galaxies and quasars, which could be used for constraining it. We study the detection limits of PNG from the surveys of the LAMOST telescope. The cases of the main galaxy survey, the luminous red galaxy (LRG) survey, and the quasar survey of dif- ferent magnitude limits...  相似文献   

A possible explanation for the electron/positron excess of ATIC/PAMELA     

Rui-Zhi Yang  Jin Chang  Jian Wu Purple Mountain Observatory  Chinese Academy of Sciences  Nanjing  China 《中国天文和天体物理学报》2010,10(1)

Results from PAMELA and ATIC indicate that the Kaluza-Klein type dark matter particles could be the annihilation source of the observed excess of electrons and positrons.Assuming the existence of a nearby black hole with 10000–100000 solar masses and a point source boost algorithm,we apply the standard propagation model and find that the results fit the data well.  相似文献   

法国高层大气所空间综合孔径项目研究进展     

伏西洋  郭红锋 《天文研究与技术》2010,7(1)

概述了法国高层大气所空间综合孔径项目背景、科学目标以及有效载荷,介绍了该项目演示系统的基本工作原理,探讨了该演示系统的望远子系统、指向子系统、共相子系统和成像子系统,并分别给出了该演示系统在非共相控制和共相控制情况下对半导体激光器和白光点光源的成像结果,实验结果表明演示系统不同独立望远镜之间已经基本实现了共相成像。最后对该演示系统进行了总结,并指出该系统可以进一步优化之处。该演示系统对我国综合孔径成像实验研究具有一定的借鉴意义。  相似文献   

用于测量圆顶视宁度的微温脉动仪的研制     

王红帅  李志  刘威卫 《天文研究与技术》2010,7(1)

为评价云南天文台丽江2.4m望远镜的圆顶视宁度,研制了一种能测量温度、气压和微温脉动的仪器。在天文圆顶附近,望远镜前方光路上,放置几组微温传感器,可以测得圆顶附近影响天文观测的湍流强度的分布情况。介绍了这套仪器的基本原理,电路设计,程序设计,实验定标以及一个简单的测试。  相似文献