检索结果-南通市图书馆

Avoided crossings between non-radial modes in low mass RGB stars

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2012年第12期12卷 1655-1665页

作者： Jun-Jun Guo1,2.3,Yan Li1,2.and Xiang-Jun Lai1,2.1 National Astronomical Observatories/Yunnan Observatory,chinese academy of Sciences,{2.,china 2.Key laboratory for the structure and evolution of celestial objects,chinese academy of Sciences,{12. 650011,china 3 Graduate University of chinese academy of Sciences,Beijing 100049,china National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 650011 China Key laboratory for the {2. and evolution of celestial objects Chinese Academy of Sciences Kunming 650011 China Graduate University of chinese academy of Sciences Beijing 100049 China

Non-radial p modes and g modes appear simultaneously in red giant stars. Their frequencies have different variation rates,causing their frequencies to become close during stellar evolution so that avoided crossings *** separation between regions where acoustic waves and gravity waves propagate for l=1,2.and 3 is different,which results in the coupling efficiency also being *** present the results of numerical computations of the models we *** find that the two kinds of modes for l=2.and 3 need to be closer in frequency in order for a complete exchange to occur,compared to the case for modes with l=*** scaled oscillation frequencies also present better regularity with evolution than modes with l=1. In order to study the effect of the avoided crossings in detail,we set the mode which has the smallest mode inertia to be the p *** plot the two kinds of modes for l =1,2.and 3 in frequency and periodéchelle diagrams and find modes of l=2.and 3 fit the two relations better;th{2. are more equally spaced in frequency and period than modes with l=*** careful observation of the two kinds oféchelle diagrams for l=2.and 3,we still find that some p modes shift a little from being equally spaced in frequency and some g modes,which are close to those p modes in period,shift a little from being equally spaced in ***,we study the relation between the deviation from period being equally spaced and the mode inertia of g modes for different *** g modes of l=1 with a period closer to the p mode have less inertia and the deviation is bigger in the periodéchelle *** deviation is also obvious. However g modes of l=2.and 3 shift a little or have almost no deviation from being equally spaced in period,even though some of them may have strong coupling and close mode inertia like in the p ***,we suggest a possible method for measuring period spacing of g modes precisely using mixed g modes with l=2.and 3 that have fewer observed mixed g m

关键词： stars:oscillations-stars:red giants

Birthrates and delay times of Type Ia supernovae

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第3期53卷 586-590页

作者： WANG Bo1,2.3, LIU ZhengWei1,2.3, HAN YunKun1,2.3, LEI ZhenXin1,2.3, LUO YangPing1,2.3 & HAN ZhanWen1,2.1National Astronomical Observatories/Yunnan Observatory, chinese academy of Sciences,{2., china 2.ey laboratory for the structure and evolution of celestial objects, chinese academy of Sciences,{2., china 3Graduate University of chinese academy of Sciences, Beijing 100049, china National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming China Key laboratory for the {2. and evolution of celestial objects Chinese Academy of Sciences Kunming China Graduate University of chinese academy of Sciences Beijing China

Type Ia supernovae (SNe Ia) play an important role in diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology. However, the nature of the progenitors of SNe Ia is still unclear. In this paper, according to a detailed binary population synthesis study, we obtained SN Ia birthrates and delay times from different progenitor models, and compared them with observations. We find that the Galactic SN Ia birthrate from the double-degenerate (DD) model is close to those inferred from observations, while the birthrate from the single-degenerate (SD) model accounts for only about 1/2.2.3 of the observations. If a single starburst is assumed, the distribution of the delay times of SNe Ia from the SD model is a weak bimodality, where the WD + He channel contributes to the SNe Ia with delay times shorter than 100 Myr, and the WD + MS and WD + RG channels to those with age longer than 1 Gyr.

关键词： binaries: close stars: evolution supernovae: general white dwarfs

A statistical study of the relation between soft X-ray excess and accretion disk

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 102-105页

作者： LIU Jieying1,2.3 & QIAO ErLin1,2.1 National Astronomical Observatories/Yunnan Observatory,chinese {2. of Science,kunming 650011,china 2.Key laboratory for the structure and evolution of celestial objects,chinese {2. of Sciences,kunming 650011,china 3 Graduate University of chinese {2. of Sciences,Beijing 100049,china National Astronomical Observatories/Yunnan Observatory Chinese Academy of Science Kunming China Key laboratory for the {2. and evolution of celestial objects Chinese Academy of Sciences Kunming China Graduate University of chinese academy of Sciences Beijing China

To study the origin of the soft X-ray excess,we compile a sample of 94 unobscured,radio-quiet QSOs and Seyfert galaxies with available data from GALEX and *** find that 50 sources show strong soft X-ray excess and the other 44 show weak/no soft X-ray *** analyses of the data indicate that the difference in soft X-rays is mainly but not only resulting from different accretion rates(in units of Eddington rate).The statistical study of the sources with soft X-ray excess shows that the strength of soft X-ray excess weakly and positively correlates with the Eddington ratio and increases with the increase of the strength of UV radiations relative to the *** that the UV emissions are from the thin disk,the correlations imply that the origin of soft X-ray excess is associated with the thin disk,either by means of Comptonization of the disk photons or in some other ways.

关键词： accretion:accretion disks ultraviolet:galaxies X-rays:galaxies

Multi-epoch X-ray observations of the narrow-line Seyfert 1 galaxy SDSS J160508.87+32.92..4 with XMM-Newton

在线全文

学校读者我要写书评

暂无评论

Science china(Physics,Mechanics & Astronomy) 2010年第S1期53卷 207-211页

作者： AI YanLi1,2.3,YUAN WeiMin1,2.ZHOU HongYan4,5 & WANG JianGuo1,2.3 1 National Astronomical Observatories/Yunnan Observatory,chinese academy of Sciences,{2. 650011,china 2.Key laboratory for the structure and evolution of celestial objects,chinese academy of Sciences,{2. 650011,china 3 Graduate University of the chinese academy of Sciences,Beijing 100049,china 4 Center for Astrophysics,University of Science and Technology of china,Hefei 2.002.,china 5 Joint Institute of Galaxies and Cosmology,SHAO and USTC,Shanghai 2.0030,china National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming China Key laboratory for the {2. and evolution of celestial objects Chinese Academy of Sciences Kunming China Graduate University of the chinese academy of Sciences Beijing China Center for Astrophysics University of Science and Technology of China Hefei China Joint Institute of Galaxies and Cosmology SHAO and USTC Shanghai China

We present results of multi-epoch XMM-Newton observations separated by several years of the narrow-line Seyfert 1(NLS1) galaxy,SDSS J160508.87+*** NLS1 showed X-ray flux variations on timescales of years as well as low amplitude variations on timescales as short as hours,while the X-ray spectral shape remained essentially *** spectrum shows a significant soft X-ray *** model of reflection from an ionized disc,that is dominant in the whole XMM-Newton bandpass,provides the best description of the observed spectra for all the observations,though alternatives such as Compton scattering(T-0.2. keV) cannot be ruled out in a statistical *** the disc reflection model,the observed variations may originate either from the change in the reflection fraction,or from the variability of the intrinsic X-ray luminosity.

关键词： galaxies:active Seyfert X-rays individual

在线全文

学校读者我要写书评

暂无评论

一种新的测量大气折射的方法

云南大学学报（自然科学版） 2018年第2期40卷 287-294页

作者：苏婕张益恭杨磊冒蔚中国科学院云南天文台云南昆明650216 中国科学院天体结构与演化重点实验室云南昆明650216 中国科学院天文大科学研究中心北京100012 中国科学院大学北京100049

大气折射是直接影响地面天体测量位置的一项较大的修正项.现有的大气折射表仅采用某一地区的大气平均密度编制而成,而实际大气密度的分布情况还受到观测站的地理环境、周围建筑物分布、气象环境等要素的影响.因此对于高精度的观测,仅用... 详细信息

大气折射是直接影响地面天体测量位置的一项较大的修正项.现有的大气折射表仅采用某一地区的大气平均密度编制而成,而实际大气密度的分布情况还受到观测站的地理环境、周围建筑物分布、气象环境等要素的影响.因此对于高精度的观测,仅用统一的大气折射表作修正是不够的,提高大气折射修正值精度的根本途径是建立观测站本地的大气折射实测模型.根据多功能天文经纬仪的特点,提出一种仅用子午方向的视天顶距测定值就可得到瞬时天文纬度测定值的方法,将这种测定值分别用于建立子午方向大气折射实测模型和各给定方位的大气折射实测模型.并且在编制观测纲要时满足一定的限制条件Σtan z→0,巧妙地压缩原有大气折射表等系统误差对瞬时天文纬度测定值的影响.

关键词：天体测量天文大气折射数据处理

在线全文

学校读者我要写书评

暂无评论

略论朱熹对浑仪的研究

上饶师范学院学报 2004年第5期24卷 17-20,45页

作者：乐爱国胡行华徐平厦门大学，福建厦门361005 不详

宋代理学家朱熹研究过天文学,而且有充分的史料证明"朱熹家有浑仪"。朱熹对浑仪的发展历史以及浑仪的结构有过深入的研究,并作了详细的描述。更为重要的是,他运用浑仪研究天的北极、北极星以及其它天文现象,以诠释儒家经典中的天文知识... 详细信息

宋代理学家朱熹研究过天文学,而且有充分的史料证明"朱熹家有浑仪"。朱熹对浑仪的发展历史以及浑仪的结构有过深入的研究,并作了详细的描述。更为重要的是,他运用浑仪研究天的北极、北极星以及其它天文现象,以诠释儒家经典中的天文知识,从而表现出朱熹既是理学家又是天文学家的双重身份。

关键词：朱熹儒家经典宋代理学诠释理学家描述天文知识证明北极星发展历史