共查询到20条相似文献,搜索用时 125 毫秒
1.
分析1985年EXOSAT卫星对银河核球X射线源GX9+1的观测数据,发现该源存在几百秒量级的振荡现象,这一结果有助于了解小质量X射线双星GX9+1的吸积特性和轨道运动。 相似文献
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在此介绍我们基于ASCA 和ROSAT 等X 射线天文卫星,对3C397 、G327 .11 .1 、G21 .50 .9 和RXJ1713 .73946 等超新星遗迹的物理特性进行的分析,简要地讨论了3C397 的非平衡电离双热分量和双极泡结构以及G327 .11 .1 和G21 .50 .9 中隐匿脉冲星的性质,并提出RXJ1713 .73946 和AD393 客星之间可能的关系。 相似文献
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光学观测表明,致密星系群SCGG 223中成员星系的速度弥散高达1106km/s,并且 整个星系群处于平衡状态.星系群的数值模拟也显示, SCGG 223是维里化的.这些光学 波段上的研究结果暗示, SCGG 223可能具有星系团量级的大引力质量,其星系际气体则 很可能处在极高温的状态.为了证实这些推测,作者在 1999年 2月利用 ASCA卫星对 SCGG 223进行了 X射线观测.通过光谱分析,获得了它的气体温度和 0.5~10 keV波段 上的光度分别为kT=1.4_(-0.4)~(+.6): keV和9.85_(-2.04)~(6.11)× 1036J S-1.与光学观测所作出的预计相 反,这些数值显示 SCGG 223是一个正常的低温星系群.由于 SCGG 223在 0.5~10 keV 波段上很暗,无法从ASCA获得的X射线表面亮度分布推算其总引力质量,因此,尚不 能直接判断它的质量是否真的像光学维里质量那样大. 相似文献
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利用日本YOHKOH卫星HXT提供的HXR爆发资料,和中国科学院北京天台的大亨是射电宽频带动态频谱仪(1.0-2.0GHz,2.6-3.8GHz)提供的微波爆发资料,对共生事件进行了初步统计分析,并对其中两例典型事件:1997年11月28日0503UT事件及1998年5月9日0340UT事件与共生的HXR爆发进行了详细比较,给出了几点有意义的结果及理论解释。 相似文献
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XPer的新发射相:光谱与红外观测 总被引:1,自引:0,他引:1
XPer的新发射相:光谱与红外观测杭恒荣,夏剑萍中国科学院紫金山天文台,南京210008中国科学院光学天文联合实验室关键词Be星/X射线双星,发射线,JHK测光1引言XPer是一颗Be/X射线双星(4U0352+30)的光学对应体[1-3],中子星的... 相似文献
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脉冲星PSR1951+32的X射线脉冲辐射程凌翔,李惕碚,孙学军,马宇蒨,吴枚(中国科学院高能物理研究所,北京100039)主题词:脉冲星-X射线源1987年6月,用频率387MHz的射电观测发现了脉冲星PSR1951+32[1],同年7月,在180... 相似文献
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1995年5月,使用2.16m望远镜对ROSAT X射线源进行光学证认期间,发现8个ROSAT X射线源和5G射电源的光学对应体是以前未发现的类星体,其红移范围从0.333至1.091。本文给出了这些类星体的多波段特性。 相似文献
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XRB、SGR和GRB简介X射线爆发(X-rayBursters,以下简称XRB)、软γ射线复现(Soft-gammaRepeaters,以下简称SGR)和γ射线爆发(γ-raaBursters,以下简称GRB)都是天空中暂现、转瞬即逝的高能现象,三... 相似文献
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从ROSAT PSPC观测数据中我国发现了与PSR0355+54相关联的脉冲星X射线喷流存在的证据。这是一个与脉冲星自行方向相反的长度为12′的近似线性的辐射特征。假设喷流具有PSR0355+54相同的距离和星际吸收,而其能谱是谱指数为-0.5的幂律谱,可导出喷流的光度为2.48±0.83×10^24J/S。喷流中的平均磁场约为7.9×10^-9T,典型的电子能量为2.1×10^7MeV。 相似文献
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J'erôme P'etri 《Astrophysics and Space Science》2006,302(1-4):117-139
This is the second of a series of papers aimed to look for an explanation on the generation of high frequency quasi-periodic
oscillations (QPOs) in accretion disks around neutron star, black hole, and white dwarf binaries. The model is inspired by
the general idea of a resonance mechanism in the accretion disk oscillations as was already pointed out by Abramowicz and
Klu’zniak (2001). In a first paper (P'etri, 2005a, paper I), we showed that a rotating misaligned magnetic field of a neutron
star gives rise to some resonances close to the inner edge of the accretion disk. In this second paper, we suggest that this
process does also exist for an asymmetry in the gravitational potential of the compact object. We prove that the same physics
applies, at least in the linear stage of the response to the disturbance in the system. This kind of asymmetry is well suited
for neutron stars or white dwarfs possessing an inhomogeneous interior allowing for a deviation from a perfectly spherically
symmetric gravitational field. After a discussion on the magnitude of this deformation applied to neutron stars, we show by
a linear analysis that the disk initially in a cylindrically symmetric stationary state is subject to {three kinds of resonances:
a corotation resonance, a Lindblad resonance due to a driven force and a parametric resonance}. In a second part, we focus
on the linear response of a thin accretion disk in the 2D limit. {Waves are launched at the aforementioned resonance positions
and propagate in some permitted regions inside the disk, according to the dispersion relation obtained by a WKB analysis}.
In a last part, these results are confirmed and extended via non linear hydrodynamical numerical simulations performed with
a pseudo-spectral code solving Euler's equations in a 2D cylindrical coordinate frame. {We found that for a weak potential
perturbation, the Lindblad resonance is the only effective mechanism producing a significant density fluctuation}. In a last
step, we replaced the Newtonian potential by the so called logarithmically modified pseudo-Newtonian potential in order to
take into account some general-relativistic effects like the innermost stable circular orbit (ISCO). The latter potential
is better suited to describe the close vicinity of a neutron star or a black hole. However, from a qualitative point of view,
the resonance conditions remain the same. The highest kHz QPOs are then interpreted as the orbital frequency of the disk at
locations where the response to the resonances are maximal. It is also found that strong gravity is not required to excite
the resonances. 相似文献
14.
The effect of cold plasma injection on whistler mode instability has been studied separately for a bi-Maxwellian and a loss-cone hackground plasma with perpendicular AC electric field. The cold plasma is described by a simple Maxwellian distribution, whereas a generalized distribution function with index j that reduces to a bi-Maxwellian for j = 0 and to a loss-cone for j = 1 has been derived for a plasma in the presence of a perpendicular AC electric field, to form a hot/warm background. The dispersion relation is obtained using the method of characteristic solutions and kinetic approach. An expression for the growth rate of a system with added cold plasma injection has been calculated. Results of sample theoretical calculations for representative values of parameters suited to the magnetosphere of Uranus has been obtained. The salient features of the analysis and the results obtained in both cases have been compared and discussed. It is inferred that it is not the magnitude but the frequency of the AC field which influences the growth rate and a loss-cone background plasma has a triggering effect on the growth rate, increasing the value of the real frequency and maximum growth rate by an order of magnitude. These results may go a long way to enable one to get a better understanding of whistlers and diagnostics of plasma parameters in the Uranian magnetosphere. 相似文献
15.
E. García L. De Haro C. O'Sullivan G. Cahill J. A. López Fernández F. Tercero B. Galocha J. L. Besada 《Experimental Astronomy》2003,15(3):173-193
A classical radioastronomy receiver is fed with a corrugated horn and an independent lens, both placed in a cryostat to lower
the noise temperature. The beam is focused and directed using a combination of elliptical and plane mirrors. This paper proposes
modifying the initial feeding system by placing the lens onto the horn aperture, thereby allowing a size reduction of the
horn and lens, and a simplification of their mechanical design. The profiled lens is shaped to correct the phase error on
the horn aperture. A quasi-optical model of the horn-plus-lens system has been developed using a Beam Mode Expansion (BME).
Results using both a hyperbolic-planar lens and a spherical-elliptical lens, as well as results obtained by using Geometrical
Optics (GO) with a Kirchoff–Huygens integration to get the far-field pattern, have been compared with measurements. As a direct
application, a full focusing system for the new 40-m radiotelescope at the “Centro Astronómico de Yebes” is presented for
the 22, 30 and 45 GHz bands. This paper has developed a QO model for a corrugated conical horn with a phase-correcting lens.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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David J. Ampleford Andrea Ciardi Sergey V. Lebedev Simon N. Bland Simon C. Bott Jeremy P. Chittenden Gareth N. Hall Adam Frank Eric Blackman 《Astrophysics and Space Science》2007,307(1-3):29-34
We present experimental data on the steady state deflection of a highly supersonic jet by a side-wind in the laboratory. The
use of a long interaction region enables internal shocks to fully cross the jet, leading to the development of significantly
more structure in the jet than in previous work with a similar setup (Lebedev et al., 2004). The ability to control the length
of the interaction region in the laboratory allows the switch between a regime representing a clumpy jet or wind and a regime
similar to a slowly varying mass loss rate. The results indicate that multiple internal oblique shocks develop in the jet
and the possible formation of a second working surface as the jet attempts to tunnel through the ambient medium. 相似文献
18.
M. G. Abrahamyan 《Astrophysics》2009,52(1):119-131
The nonlinear dynamics of a rotating jet is examined following its ejection from a compact gravitating object by a vortex
mechanism. A scenario is described in which a dense stream expands and is subsequently transformed into a nonstationary vortex
consisting of a cylindrical core and a “sheath.” At this stage of development, a converging radial flow of matter in the differentially
rotating nonuniform sheath collimates the jet and speeds up the rotation of the core, as well as the flow of matter along
the jet, in accordance with a power law or “explosive” instability, until the velocity discontinuity at the surface of the
core approaches the sound speed. Flows of this type have low energy dissipation and can serve as unique channels for the acceleration
and collimation of jet eruptions from young stars, active galactic nuclei, and quasars.
Translated from Astrofizika, Vol. 52, No. 1, pp. 135–145 (February 2009). 相似文献
19.
A. Budovičová S. Štefl P. Hadrava Th. Rivinius O. Stahl 《Astrophysics and Space Science》2005,296(1-4):169-172
o And is one of the most frequently observed Be stars, both in photometry and spectroscopy. It is a multiple system of at least four stars (a Be star, a close binary of spectral types B7 and B8, and an A star). For over a century, numerous observers report a highly variable spectrum, photometric changes, and a substantial range of radial velocity. The star has changed back and forth between a shell-type and a normal B-type star. The last emission phase started in 1992 and ended in 2000. Analysis of the dynamical spectra at spectral lines Mg II 4481 Å and He I 6678 Å and radial velocity curves shows that the two binary components can be resolved. We decomposed the triple star spectra and computed orbital parameters of the binary companion using the KOREL code for spectrum disentangling. 相似文献