共查询到20条相似文献，搜索用时 406 毫秒
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为研究古代的恒星位置观测,用矩阵转换方法计算了1800颗亮星从公元前1051年到公元2050年的平位置(每世纪给出一值)赤道和黄道坐标。文中讨论了计算方法,介绍了计算过程、资料来源和精度估计,给出恒星目录及几颗星的例表和例图。 相似文献
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狐狸座PU是1979年4月8日由日本东京天文台Y.Kuwano等人首先发现的一颗光度变化特殊的类新星天体.1978—79年间,梅苞在用北京天文台40/200双筒天体照相仪对这一天区的其他天体作系统观测时,同时取得了这颗星的一批照相观测资料,在获悉有关这颗星的发现报道之前,他也曾独立地发现了这颗星的光度变化(图版Ⅰ,图2),并随即用北京天文台的60/90/1800施密特望远镜有缝摄谱仪取得了该星的部分光谱资料.此外,还用北京天文台60厘米反射望远镜进行了高速光电观测.从1978年12月到1983年3月,共取得照相观测底片和光谱片200余张以及一些光电测光资料. 相似文献
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我们从1981年9月至1983年12月对PU Vul进行了光谱观测,本文描述了其主要光谱特征及其变化。1981年9月PU Vul的光谱上只有吸收线,1982年10月出现很强的H_α发射线,1983年9月1日又出现H_β发射线,1983年10月H_α和H_β变得更强,11月发射线开始变弱,12月H_β发射线似已消失,但H-α发射线还是很强。整个观测期间该星光谱型基本与F型巨星相近。 这颗星很可能是一颗变化特别慢的慢新星,而且可能是由一颗M型巨星和一颗低光度的热子星组成的双星。 相似文献
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从1981年开始,北京天文台开展了发射线星系的物端稜镜巡天。用60/90cm Schmidt望远镜加5.°3的物端稜镜在敏化的ⅢaJ底片上可以得到亮于16~m的星系光谱像。本文公布了第一批巡天结果:在覆盖天区约220平方度的12张底片上证认出50个发射线天体,47个河外星系(其中3个可能是新的Seyfert星系),3个行星状星云(其中一个N2242以前被当作河外星系)。文中给出了这些天体的名称、坐标、星等及光谱结构分类等资料,并比较系统地讨论了发射线星系的证认及光谱结构分类。我们还将本巡天的结果与其他天文台的结果作了比较。这些天体的证认图见图版Ⅰ—Ⅱ。 相似文献
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对29颗Be星作了近红外JHK宽波段测光。所选对象多少有些特殊性。其中19颗有或可能有快周期光变,6颗是Be/x射线双星。观测用光学天文开放实验室北台兴隆站1.26米红外望远镜。观测结果表明相当多的星有较大的红外超,其中8颗星的J-K值大于0.5;有3颗星有较明显变化,△(J-K)大于0.4。 相似文献
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最近，一个困扰人们达十几年之久的γ射线源Ｇｅｍｉｎｇａ被证认为Ｘ、γ射线脉冲星，其光学对应体也被确定为一颗光谱偏蓝的２５等星。对Ｇｅｍｉｎｇａ脉冲星的确证说明存在着一类没有射电辐射的脉冲单星。 相似文献
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Low-dispersion spectra are presented for six Me stars. No. 1 may be a new Mira variable. Emission line data and spectral types are given for No. 3 (probably SW Cam) and No. 5 (SV Leo). 相似文献
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High dispersion CCD spectra are used to study the profiles of the Hα and Hβ lines of 48 stars in early spectral classes in
the young diffuse binary cluster h/χ Per. In addition, moderate resolution spectra of 15 B and Be stars were taken over the
interval 4400–4960 Å. One or, possibly, two new Be stars are discovered. The major parameters of the Hα line are measured
for the observed B and Be stars. The spectra over 4400–4960 Å are used to estimate Teff, logg, and υsin i. No traces of emission are detected in the Hα line profiles for 28 of the stars and emission is observed in the Hα line
for 20. During our observations an absorption profile of the Hα line was observed for some of the stars, such as Oo146, Oo566,
Oo922, and Oo1268, although they have previously been identified as Be stars. A significant long-term variability of the Hα
line is discovered for the Be stars Oo1161 and Oo2242. Oo2371 manifests a variability in its faint emission spectrum which
is typical of close binary systems that include a Be star.
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Translated from Astrofizika, Vol. 51, No. 2, pp. 305–319 (May 2008). 相似文献
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We study spectra of 18 active stars and stellar systems, drawn from lists of known active binaries or newly discovered extreme-ultraviolet and soft X-ray sources. Using spectral synthesis and template modelling, we measure (often for the first time) a variety of physical properties of the stars, including spectral types, luminosities and v sin i values. We report direct observation of previously undetected secondary components in three systems, and refine the orbital elements for two of these (HR 7275 and HD 217344). 相似文献
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D. Montes 《Astrophysics and Space Science》1998,263(1-4):275-278
I have compiled here the three libraries of high and mid-resolution optical spectra of late-type stars I have recently published.
The libraries include F, G, K and M field stars, from dwarfs to giants. The spectral coverage is from 3800 to 1000 Å, with
spectral resolution ranging from 0.09 to 3.0 Å. These spectra include many of the spectral lines most widely used as optical
and near-infrared indicators of chromospheric activity. The spectra have been obtained with the aim of providing a library
of high and mid-resolution spectra to be used in the study of active chromosphere stars by applying a spectral subtraction
technique. However, the data set presented here can also be utilized in a wide variety of ways. A digital version of all the
fully reduced spectra is available via FTP and the World Wide Web (WWW) in FITS format.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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We present high‐quality spectra of the majority of stars that have been classified as Oe and find that their published spectral types are generally too early, most likely due to infilling of He I lines. As a matter of fact, all stars classified as Oe actually fall inside the range O9–B0 with the important exception of HD 155806 (O7.5 III) and perhaps HD 39680 (difficult to classify, but likely O8.5V). Observations of a sample of objects with published spectral types in the O9–B0 range previously classified as peculiar or emission‐line stars fail to reveal any new Oe star with spectral type earlier than O9.5. Most objects classified as peculiar in “classical” literature show signs of binarity in our spectra, but no spectral anomalies. We conclude that there is likely a real decline in the fraction of Be stars for spectral types earlier than B0, not due to observational bias. The few Oe stars with spectral types earlier than O9.5 deserve detailed investigation in order to provide constraints on the physical reasons of the Be phenomenon. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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《天文和天体物理学研究(英文版)》2015,(8)
In this work, we select spectra of stars with high signal-to-noise ratio from LAMOST data and map their MK classes to the spectral features. The equivalent widths of prominent spectral lines, which play a similar role as multi-color photometry, form a clean stellar locus well ordered by MK classes. The advantage of the stellar locus in line indices is that it gives a natural and continuous classification of stars consistent with either broadly used MK classes or stellar astrophysical parameters. We also employ an SVM-based classification algorithm to assign MK classes to LAMOST stellar spectra. We find that the completenesses of the classifications are up to 90% for A and G type stars, but they are down to about 50% for OB and K type stars. About 40% of the OB and K type stars are mis-classified as A and G type stars,respectively. This is likely due to the difference in the spectral features between late B type and early A type stars or between late G and early K type stars being very weak. The relatively poor performance of the automatic MK classification with SVM suggests that the direct use of line indices to classify stars is likely a more preferable choice. 相似文献
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We separate and analyse the component spectra of the composite‐spectrum binary HD 208253. We find that the cool primary is an evolving star of spectral type G7 III, while its hot secondary is an early‐A dwarf. The giant is currently near the lowest point of the red‐giant branch and is slightly less luminous than its dwarf companion. We provide a set of precise radial‐velocity measurements for both stars. The double‐lined orbit which we derive from them shows that the component mass ratio is close to unity (q = 1.05 ± 0.01). We deduce the physical properties of both stars, determine their respective masses to be 2.75 ± 0.07 Me (giant) and 2.62 ± 0.07 Me (dwarf), and show that the orbit's inclination is within a degree or two of 68°. The spectrum of the A‐type component has quite component has quite narrow lines (we infer a rotational velocity of 18 km s–1), though since the period of the orbit is well over 1 year that component cannot be in synchronous rotation. An intriguing property of the dwarf is its enhanced Sr and Ba, though it does not exhibit the other spectral peculiarities that would signal a classical Am star. While by no means unique amongst the multitude of oddities exhibited by A and early‐F stars, this dwarf which we have uncovered in a long‐period binary offers valuable constraints and challenges to stellar‐evolution theory. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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K. Pavlovski D. E. Holmgren P. Koubský J. Southworth S. Yang 《Astrophysics and Space Science》2006,304(1-4):329-332
Recent theoretical calculations of stellar evolutionary tracks for rotating high-mass stars suggests that the chemical composition of the surface layers changes even whilst the star is evolving on the Main Sequence. The abundance analysis of binary components with precisely known fundamental stellar quantities allows a powerful comparison with theory. The observed spectra of close binary stars can be separated into the individual spectra of the component stars using the method of spectral disentangling on a time-series of spectra taken over the orbital cycle. Recently, Pavlovski and Hensberge (2005, A&A, 439, 309) have shown that, even with moderately high line-broadening, metal abundances can be derived from disentangled spectra with a precision of 0.1 dex. In a continuation of this project we have undertaken a detailed abundance analysis of the components of another two high-mass binaries, V453 Cyg, and V380 Cyg. Both binaries are well-studied systems with modern solutions. The components are close to the TAMS and therefore very suitable for an observational test of early mixing in high-mass stars. 相似文献
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We present quantitative analyses of 7 galactic O stars of spectral types from O3 to O6. By means of classical hydrostatic
and planeparallel models we find the so-called He and Mass Discrepancies for a number of stars of our sample. We also prove
the need of line-blocking for the correct reproduction of these spectra. For stars with effective temperature around 50 000
K and above, there is no possibility of reproducing their spectra with these kind of models. Further analyses with unified
models, including sphericity and mass loss, allow us to reproduce even the earliest spectra. They also show that the Mass
Discrepancy is not only due to the neglect of sphericity and mass loss in the planeparallel analysis, and give us the mass
loss rate of these stars. We find that HD15 570, with a present mass of 100 M⊙, can be the most massive star known in the solar neighbourhood.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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We studied the spectra of 24 flare stars of the Pleiades cluster region obtained on the 2.6m telescope of the Byurakan observatory in the years 1986–1989. From the spectral indices of titanium oxide (TiO) and other chemical elements of the stars investigated we determined their spectral classes and luminosities (absolute visual stellar magnitudes). The agreement of these moduli of the stars with the distance modulus of the Pleiades cluster confirms that 21 of them belong to the cluster. Only three of them (FSP 169, FSP 377, and FSP 435) are possibly not members of the cluster. This indicates that the flare activity of a star is a reliable criterion for its membership in a nearby stellar system (cluster or association).Translated fromAstrofizika, Vol. 37, No. 4, 1994. 相似文献