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1.
Ｂe单星和Ｂe／Ｘ射线双星作为一类特殊早型天体和特殊的大质量Ｘ射线双星,在各个波段都有与其它相同光谱型的Ｂ型天体显著不同的特征,因此长期以来引起中外天文学者的关注。首先在可见光波段发射线的存在,就是对仅产生吸收线的经典大气的挑战;其次Ｂe星作为一类早型带有包层天体,研究Ｂe星包层的性质,对研究原恒星包层性质和进一步了解早 型星其它光谱型的性质是非常重要的;再者可以研究Ｂe星的存在与星际磁场或湍流的星际 相似文献
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<正>X射线是高能天体物理的重要研究波段,研究天体的X射线辐射对认识它们的形成和演化、限制宇宙中的恒星形成历史、研究星系的形成和演化等等具有重要意义.在本文中,作者以X射线双星、特别是含有白矮星为致密吸积星的X射线点源为对象,通过数值计算和观测两种手段,研究这类源形成和演化中的一些重要过程、演化产物、和Ia型超新星可能的前 相似文献
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为解释Ｂｅ／Ｘ射线双星波段联合观测结果，已发展了许多理论模型。在本文中简述这些Ｂｅ／Ｘ射线双星理论模型的研究现状，包括枞两个正常的Ｂ型星组成的密近双星演化成为Ｂｅ／Ｘ射线双星的演化模型，描述Ｂｅ星气壳的物理模型，Ｂｅ星和中子星的性质所决定的中子星吸积方式的吸积量及Ｂｅ／Ｘ射线双星Ｘ射线源光变曲线的理论解释。 相似文献
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介绍了Be星的基本特性．评述了近年来对Be星星周物质结构研究的成果．重点介绍了最新的关于Be星星周盘产生和变化的动力学模型．另外，对Be／X射线双星系统的研究也做了简要评述，重点论述了致密星与Be星延伸大气的相互作用． 相似文献
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对Be／X射线双星LSI＋65°010／2S0114＋65连续四年（1992—1995年）的光学光谱观测发现,在1992年11月它的Ha发射线等值宽度在4天内从－0．43A增至－1．48A,增加了约3．5倍．此剧烈变化支持LSI＋65°10的光学子星是一颗Be星而非超巨星的论点．我们的观测还发现,1994年9月它的Ha发射线轮廓呈明显的双峰结构,但与普通Be星中由于旋转气壳而形成的双峰不同,其红峰处于Ha理论波长附近,紫峰却紫移了7．2A．我们认为此双峰可能产生在LSI＋65°010的不同HⅡ区中,即红峰产生于Be星周围的气壳内,而紫峰很可能产生于在轨道上快速运动的中子星周围的HⅡ区中,此观测可能提供了中子星周围存在HⅡ区的证据．同样,我们认为1992年11月4日观测到的Ha发射线红翼几乎不变,紫翼却大幅增加的现象也是由于中子星周围的HⅡ区造成的． 相似文献
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磁星(magnetar)是一类有着极强磁场的致密天体,它们的外部磁场强度是典型中子星磁场强度的100～1 000倍。在过去几十年中,软γ射线复现源(SGR)和反常X射线脉冲星(AXP)被认为是最有可能的磁星候选者。磁星有着独特的能谱性质和光变特征,它的观测现象丰富多彩,其观测波段跨越了射电、红外、光学、X射线和γ射线等。近些年来,多种理论模型也相继被提出来,以解释其独特的性质。以正常脉冲星为例,介绍了磁星与通常中子星的不同性质,详述了磁星在多波段的能谱、光变及周期跃变现象等观测特性,总结了为解释磁星的特殊性质而建立起来的多种理论模型,并详述了中子星框架下的扭曲磁层模型。此外还介绍了其他候选模型。 相似文献
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通过光谱观测获得53颗Be星的自转速度Vsir.i,在Hutchings的方法基础上估算出V和i。我们分析了自转对发射线宽度的影响,利用发射线峰间间隔求取气壳与光球的半径比和稀化因子。文中着重讨论了快自转而且存在恒星风的自转模型同Be现象之间的关系。 相似文献
9.
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
10.
非团环境中的大质量恒星以及大质量双星的起源是理解大质量恒星形成和演化的关键问题之一. 年轻大质量星团内的动力学交会过程是产生大质量逃逸星的重要途径之一. 选取了银河系内年轻大质量星团NGC 3603外围的两个碰撞星风系统候选体MTT68A和MTT71作为研究对象, 通过分析\emphChandra X射线观测以及\emphGaia第2批数据发布(DR2)中的天体测量结果, 研究它们作为相互作用的大质量双星系统的起源. X射线数据的分析表明, 它们的X射线能谱中存在Fe XXV发射线成分; 相较于普通O型星, 以双温等离子体模型拟合得到偏高的高温成分温度($\gtrsim$2.0keV), 并且X射线光度与热光度的比值也较高($\gtrsim10^{-5.8 相似文献
11.
Natalya Raguzova 《Astrophysics and Space Science》2002,281(3):641-649
Using the numerical code (`Scenario Machine') we study of number and physical properties of binary Be stars. Evolutionary
tracks leading to a formation of the observational binary systems are presented. We conclude that synchronization must be
taken into account when calculating binary Be star evolution and calculate the minimal orbital period for Be/evolved companion
binary. The obtained distributions over orbital parameters are in good agreement with the observational lack of short-period
Be/X-ray binaries. According to our calculations 70% of all Be stars must have a white dwarf. The white dwarfs in these systems
should be hot enough with the surface temperature distribution peaking at 10000–20000 K. Their detection is possible during
the period of the lack of Be star envelope by the detection of white dwarf extremely UV and soft X-ray emission. This method
of registration appears to be particularly promising for `single' early-type Be stars because in these systems the white dwarfs
must have a very high surface temperature. However, the loss of the Be disc-like envelope does not often occur and it is a
rather rare event for many Be stars. The best possibility of white dwarf detection is given by the study of helium spectral
lines found in emission from several Be stars. The ultraviolet continuum energy of these Be stars is found to be not enough
to produce the observed helium emission. Besides, we also discuss the orbital properties of binary Be star systems with other
evolved companions such as helium stars and neutron stars and give a possible explanation for the lack of Be/black hole binaries.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
We describe the present state of massive star research seen from the viewpoint of stellar evolution, with special emphasis
on close binaries. Statistics of massive close binaries are reasonably complete for the Solar neighbourhood. We defend the
thesis that within our knowledge, many scientific results where the effects of binaries are not included, have an academic
value, but may be far from reality. In chapter I, we summarize general observations of massive stars where we focus on the
HR diagram, stellar wind mass loss rates, the stellar surface chemistry, rotation, circumstellar environments, supernovae.
Close binaries can not be studied separately from single stars and vice versa. First, the evolution of single stars is discussed
(chapter I). We refer to new calculations with updated stellar wind mass loss rate formalisms and conclusions are proposed
resulting from a comparison with representative observations. Massive binaries are considered in chapter II. Basic processes
are briefly described, i.e. the Roche lobe overflow and mass transfer, the common envelope process, the spiral-in process
in binaries with extreme mass ratio, the effects of mass accretion and the merging process, the implications of the (asymmetric)
supernova explosion of one of the components on the orbital parameters of the binary. Evolutionary computations of interacting
close binaries are discussed and general conclusions are drawn. The enormous amount of observational data of massive binaries
is summarized. We separately consider the non-evolved and evolved systems. The latter class includes the semi-detached and
contact binaries, the WR binaries, the X-ray binaries, the runaways, the single and binary pulsars. A general comparison between
theoretical evolution and observations is combined with a discussion of specially interesting binaries: the evolved binaries
HD 163181, HD 12323, HD 14633, HD 193516, HD 25638, HD 209481, Per and Sgr; the WR+OB binary V444 Cyg; the high mass X-ray binaries Vela X-1, Wray 977, Cyg X-1; the low mass X-ray binaries Her
X-1 and those with a black hole candidate; the runaway Pup, the WR+compact companion candidates Cyg X-3, HD 50896 and HD 197406. We finally propose an overall evolutionary model
of massive close binaries as a function of primary mass, mass ratio and orbital period. Chapter III deals with massive star
population synthesis with a realistic population of binaries. We discuss the massive close binary frequency, mass ratio and
period distribution, the observations that allow to constrain possible asymmetries during the supernova explosion of a massive
star. We focuss on the comparison between observed star numbers (as a function of metallicity) and theoretically predicted
numbers of stellar populations in regions of continuous star formation and in starburst regions. Special attention is given
to the O-type star/WR star/red supergiant star population, the pulsar and binary pulsar population, the supernova rates.
Received 17 July 1998 相似文献
13.
简要地回顾了Ｂｅ／Ｘ射线双星２０多年来在红外、可见光、紫外和Ｘ射线波段所取得的观测结果，着重介绍了多波段联合观测对探讨双星间的相互作用如中子星的吸积方式和Ｘ射线产生的原因等方面的意义，对这些观测结果的分析研究，将是人们了解Ｂｅ／Ｘ射线双星的轨道参数和双星的物理参数、建立理论模型的基础。 相似文献
14.
Deborah Baines René D. Oudmaijer John M. Porter † Monica Pozzo 《Monthly notices of the Royal Astronomical Society》2006,367(2):737-753
We present high-resolution spectro-astrometry of a sample of 28 Herbig Ae/Be and three F-type pre-main-sequence stars. The spectro-astrometry, which is essentially the study of unresolved features in long-slit spectra, is shown from both empirical and simulated data to be capable of detecting binary companions that are fainter by up to 6 mag at separations larger than ∼0.1 arcsec. The nine targets that were previously known to be binary are all detected. In addition, we report the discovery of six new binaries and present five further possible binaries. The resulting binary fraction is 68 ± 11 per cent. This overall binary fraction is the largest reported for any observed sample of Herbig Ae/Be stars, presumably because of the exquisite sensitivity of spectro-astrometry for detecting binary systems. The data hint that the binary frequency of the Herbig Be stars is larger than that of the Herbig Ae stars. The Appendix presents model simulations to assess the capabilities of spectro-astrometry and reinforces the empirical findings. Most spectro-astrometric signatures in this sample of Herbig Ae/Be stars can be explained by the presence of a binary system. Two objects, HD 87643 and Z CMa, display evidence for asymmetric outflows. Finally, the position angles of the binary systems have been compared with available orientations of the circumprimary disc and these appear to be coplanar. The alignment between the circumprimary discs and the binary systems strongly suggests that the formation of binaries with intermediate-mass primaries is due to fragmentation as the alternative, stellar capture, does not naturally predict aligned discs. The alignment extends to the most massive B-type stars in our sample. This leads us to conclude that formation mechanisms that do result in massive stars, but predict random angles between the binaries and the circumprimary discs, such as stellar collisions, are also ruled out for the same reason. 相似文献
15.
M. J. Coe W. R. T. Edge J. L. Galache V. A. McBride 《Monthly notices of the Royal Astronomical Society》2005,356(2):502-514
This work represent the first major study of the optical and infrared characteristics of the mass donor companions to the X-ray pulsars in the Small Magellanic Cloud (SMC). In this work several new counterparts have been identified, and possible ones confirmed, as companions to X-ray pulsars in the SMC giving a total of 34 such objects now identified. In addition this work presents three new binary periods and confirms two X-ray periods using optical data for objects in this group. This homogeneous sample has been studied as a group to determine important general characteristics that may offer an insight into the evolution of such systems. In particular, the spectral class distribution shows a much greater agreement with those of isolated Be stars, and appears to be in some disagreement with the galactic population of Be stars in Be/X-ray binaries. Studies of the long-term optical modulation of the Be star companions reveal an extremely variable group of objects, a fact which will almost certainly make a major contribution to the pronounced X-ray variability. The spatial distribution of these systems within the SMC is investigated and strongly suggests a link between massive star formation and the H i density distribution. Finally, studies of the circumstellar disc characteristics reveal a strong link with optical variability offering important clues into the long-term stability of such discs. 相似文献
16.
The study of detached eclipsing binaries in open clusters can provide stringent tests of theoretical stellar evolutionary models, which must simultaneously fit the masses, radii, and luminosities of the eclipsing stars and the radiative properties of every other star in the cluster. We review recent progress in such studies and discuss two unusually interesting objects currently under analysis. GV Carinae is an A0 m + A8 m binary in the Southern open cluster NGC 3532; its eclipse depths have changed by 0.1 mag between 1990 and 2001, suggesting that its orbit is being perturbed by a relatively close third body. DW Carinae is a high-mass unevolved B1 V + B1 V binary in the very young open cluster Collinder 228, and displays double-peaked emission in the centre of the Hα line which is characteristic of Be stars. We conclude by pointing out that the great promise of eclipsing binaries in open clusters can only be satisfied when both the binaries and their parent clusters are well-observed, a situation which is less common than we would like. 相似文献
17.
We have detected X-ray emission (1 keV) from young intermediate-mass stars (Herbig Ae/Be stars). Since these stars are not supposed to produce intrinsic X-ray emission (no convection, no coronae), we believe that our results suggest that the X-ray emission actually traces the shock interaction of the Ae/Be star stellar winds with remnant circumstellar matter left over from the star formation process, the presence of which is also indicated by far-infrared (IRAS) and submm/mm continuum data. 相似文献
18.
M. P. E. Schurch M. J. Coe K. E. McGowan V. A. McBride D. A. H. Buckley J. L. Galache R. H. D. Corbet M. Still P. Vaisanen A. Kniazev K. Nordsieck 《Monthly notices of the Royal Astronomical Society》2007,381(4):1561-1568
We investigate the optical counterparts of recently discovered Be/X-ray binaries in the Small Magellanic Cloud (SMC). In total four sources, SXP101, SXP700, SXP348 and SXP65.8 were detected during the Chandra survey of the wing of the SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground-based telescopes have been utilized in the optical follow-up, providing coverage in both the red and blue bands. This has led to the classification of all of the counterparts as Be stars and confirms that three lie within the Galactic spectral distribution of known Be/X-ray binaries. SXP101 lies outside this distribution and is the latest spectral type known. Monitoring of the Hα emission line suggests that all the sources barring SXP700 have highly variable circumstellar discs, possibly a result of their comparatively short orbital periods. Phase-resolved X-ray spectroscopy has also been performed on SXP65.8, revealing that the emission is indeed harder during the passage of the X-ray beam through the line of sight. 相似文献