黑洞候选体X射线双星Cyg X-1光变曲线的研究

利用Rossi X-ray Timing Explorer(RXTE)卫星从1996年1月到2005年5月的公共资料,研究了黑洞候选体X射线双星Cyg X-1光变曲线的周期性,并且发现了一些有趣的周期特性(T=1．0±0．2天和T=18．0±3．0天)．在硬态时,T=1．0±0．2天和T=18．0±3．0天的周期特性同时出现在它的光变曲线之中,但在软态时仅有T=1．0±0．2天的周期出现．采用一种新的方法(即微分法),同时为了检验微分法的正确性,还利用传统的方法(即快速傅立叶变换和叠加法)分析了相同的资料,并得到了与微分法相同的结果．另外也对Cyg X-1的轨道周期进行了研究,结果发现T=5．6天的轨道周期不仅出现在硬态,同时也出现在软态,只是在硬态时比在软态时明显．     

黑洞候选体X射线双星Cyg X-1硬度比周期特性研究

利用离散傅里叶分析法,基于RXTE (Rossi X-ray Timing Explorer)/ASM(All-Sky Monitor,1.5～12 keV)观测数据,对黑洞候选体X射线双星Cyg X-1硬度比HR(5～12 keV/3～5 keV)(简写HR)的时变特性进行了分析,结果表明黑洞候选体X射线双星Cyg X-1硬度比HR存在明显的周期特性:(1)混合态(硬态+软态,本文指MJD=50087～55841期间所有的观测数据)时,HR存在T≈5.6 d、40.0 d、78.4 d、173.8 d以及400/800 d的时变周期; (2)硬态时, HR存在T≈5.6 d、33.7/67.6 d、45.3 d和165.3 d的周期特性; (3)软态时,HR出现了T≈38.5 d、48.1 d和128.3 d的周期性变化.并利用粘滞理论和Zdziarski吸积盘模型讨论了以上周期特性的物理机制.     

Cyg X-3X光子场对γ射线的吸收效应

本文详细讨论了X射线双星Cyg X-3 的X光子场对γ射线的吸收效应.计算结果表明:当Cyg x-3 的X光子发射场处于高态时,从致密中子星附近发射的能量为10~2—10~4MeV的γ射线约有60％被其吸收,吸收过程产生的正负电子的逆Compton 散射会使出射能量10—70MeV的γ射线强度平均增加约50％.计算的γ射线能谱与实验观测结果基本相符.     

武仙座X-1的硬X射线谱线

本文应用对武仙座X射线源 Her X-1新近获得的硬X射线谱线的观测资料,对辐射区域的物理情况作了初步的探讨。得到:辐射区域对谱线辐射是不透明的,激发温度T～2.4×10~8K,辐射区域的截面积～2×10~7厘米~2,并预言第三条谱线的强度约为第一条谱线的1/13,第三条谱线的宽度约为第一条谱线的3倍。     

天鹅座X-3的高能γ射线

对欧洲γ天文卫星COS-B数据的分析迄今未能发现在天鹅座X-3位置上存在着γ射线点源,从1977年6月到1980年6月,COS-B对Cyg-X天区进行了三次观测,各次观测的主要参数见表1,在第22次观测和第36次观测期间,天鹅区X-3大部分时间处于X辐射低态,各自只有6天左右处于高态;在第51次观测期间,大部分时间为X辐射高态,只有7天左右处于低态。     

Her X-1 35天开关周期是由于中子星的自由进动产生的吗?(英文)

一些作者提出Her X-1的35天开关周期是由中子星的自由进动引起的。对这个模型我们进行了理论计算,并将理论结果和观测资料进行了比较,我们发现: (1)Hcr X-1的35天周期的光变曲线的理论值与观测(Jones ＆ Forman,1976)不符。 (2)在这个模型中脉冲宽度和强度随35天周期有很大的变化(见图4和图5),也与观测不符(如Gruber等人1980年的观测)。 (3)Parmar等人(1985)报道他们没有发现预期的Her X-1的X射线辐射35天周期的变化,这也同中子星自由进动的模型不一致。 Pravdo等(1977)建议观测到的X射线脉冲是由产生于中子星表面附近的、对称的辐射束经汤姆逊散射而形成。我们用强磁场中的汤姆逊散射理论所作的分析表明,该模型可以较好地与观测相符。     

天鹅座X-3 X光子对γ射线的吸收

通过处理天文卫星COS-B的数据,我们首次获得了Cygnus X-3的γ射线像,并且发现了150—5000 MeV高能γ辐射与2—12keV X辐射强度的负相关现象,即X射线高态时的γ辐射比低态时弱. γ-X负相关现象可以用吸积盘X射线冕区中密集的X射线光子对γ射线的吸收作用解释.     

基于Jurkevich法Cyg X-1光变周期特性研究

针对天文观测数据不等间隔的特点,利用Jurkevich方法对黑洞候选体X射线双星Cyg X-1近16年的Rossi X-ray Timing Explorer(RXTE)All-Sky Monitor(ASM)数据进行了频谱分析,并结合Kidger周期存在可信度的判据,发现Cyg X-1存在363±11.5 d的光变周期,但没有发现420 d的光变周期,而且150 d的光变周期可能仅仅是51±1.4 d光变周期的观测表象。     

Cyg X-1高态中短暴性质的研究

CygX-1高能辐射的时变特征可以通过短暴(shot)的性质反映．因此CygX-1的短暴性质，特别是处于低态时的性质曾被广泛研究,利用直接叠加短暴和自相关函数，对CygX-1高态时短暴的性质进行了研究．结果表明，当CygX-1处于高态时，其短暴的结构类似于低态时所具有的性质，短暴的半高宽随能量的增加按指数下降．此结果和康普顿化模型不一致．另外，短暴的能谱演化及结构的非对称性可以解释CygX-1中的时延现象．     

The orbital period of HDE 226868/Cyg X-1

We present epoch 1996, high-quality radial velocity data for HDE 226868, the optical counterpart of Cygnus X-1. Combining our results with all published historical data, we have derived a new ephemeris for the system of HJD 245 0235.29 + n  × 5.5998, which allows accurate orbital phase calculations to be made for any X-ray observations over the last 30 years. We find no evidence for any period change such as that suggested by Ninkov, Walker &38; Yang. We discuss the shortcomings of previous work in establishing the period and orbital elements.     

Frequency-resolved spectroscopy of Cyg X-1: fast variability of the reflected emission in the soft state

Using RXTE /PCA data, we study the fast variability of the reflected emission in the soft spectral state of Cyg X-1 by means of Fourier frequency-resolved spectroscopy. We find that the rms amplitude of variations of the reflected emission has the same frequency dependence as the primary radiation down to time-scales of ≲30–50 ms. This might indicate that the reflected flux reproduces, with nearly flat response, variations of the primary emission. Such behaviour differs notably from that of the hard spectral state, in which variations of the reflected flux are significantly suppressed in comparison with the primary emission, on time-scales shorter than ∼0.5–1 s.
If related to the finite light-crossing time of the reflector, these results suggest that the characteristic size of the reflector, presumably an optically thick accretion disc, in the hard spectral state is larger by a factor of ≳5–10 than in the soft spectral state. Modelling the transfer function of the disc, we estimate the inner radius of the accretion disc to be R _in∼100 R _g in the hard state and R _in≲10 R _g in the soft state for a 10-M_⊙ black hole.     

The additional radiation of Cyg X-1 at primary minimum

New UBV-photoelectric observations of the well-known massive X-ray binary system Cyg X-1/V 1357 Cyg are obtained near the primary minimum. The detailed analysis of these observations confirms the existence of additional blue radiation which appears as a narrow peak with an amplitude of 0.01–0.02 mag near phase 0.00 on the light curve (the superior conjunction of the relativistic component), firstly detected by Lyuty (1985). This emission does not appear at every orbital cycle. The appearance of this narrow peak of additional blue radiation on the light curve of Cyg X-1 can be explained as the radiation of relativistic electrons in the disturbed magnetic field of the optical star in frames of the model proposed by Ikhsanov and Fabrika (1990).     

Rms–flux relation of Cyg X-1 with RXTE: dipping and nondipping cases

The rms (root mean square) variability is the parameter for understanding the emission temporal properties of X-ray binaries (XRBs) and active galactic nuclei (AGN). The rms–flux relation with Rossi X-ray Timing Explorer (RXTE) data for the dips and nondip of black hole Cyg X-1 has been investigated in this paper. Our results show that there exist the linear rms–flux relations in the frequency range 0.1–10 Hz for the dipping light curve. Moreover, this linear relation still remains during the nondip regime, but with the steeper slope than that of the dipping case in the low energy band. For the high energy band, the slopes of the dipping and nondipping cases are hardly constant within errors. The explanations of the results have been made by means of the “Propagating Perturbation” model of Lyubarskii (Lyubarskii, Y.E., Mon. Not. Roy. Astron. Soc. 292, 679–685 (1997)).     

The X-ray spectrum of Cyg X-2

The spectra of disc accreting neutron stars generally show complex curvature, and individual components from the disc, boundary layer and neutron star surface cannot be uniquely identified. Here we show that much of the confusion over the spectral form derives from inadequate approximations for Comptonization and for the iron line. There is an intrinsic low-energy cut-off in Comptonized spectra at the seed photon energy. It is very important to model this correctly in neutron star systems as these have expected seed photon temperatures (from either the neutron star surface, inner disc or self-absorbed cyclotron) of ≈1 keV, clearly within the observed X-ray energy band. There is also reflected continuum emission which must accompany the observed iron line, which distorts the higher energy spectrum. We illustrate these points by a reanalysis of the Ginga spectra of Cyg X-2 at all points along its Z track, and show that the spectrum can be well fitted by models in which the low-energy spectrum is dominated by the disc, while the higher energy spectrum is dominated by Comptonized emission from the boundary layer, together with its reflected spectrum from a relativistically smeared, ionized disc.     

Observation of ultra low hard X-ray flux from Cyg X-1 —A possible partial occulation of the X-ray source

The black hole candidate Cyg X-1 was observed in ultra low state on march 30, 1997 using Large Area Scintillation counter Experiment (LASE) in the hard X-ray energy region of 20–180 keV. During the 30 minute exposure a combined signal of 68 sigma was obtained, however, the measured flux at 50 keV was lower by a factor of 2 than the minimum flux reported so far. Using the recent orbital ephemeris of the source, our snap-shot observations were made at ϕ_5.6 = 0.915, which corresponds to the binary minimum revealed by the ASM light curves. The daily average data from the BATSE detectors give the source intensity level to be higher by a factor of 5. Very low flux values measured in the present experiment suggest that the hard X-ray source may have been partially occulted by the primary companion during its transit near the X-ray minimum.