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1.
利用线性状态空间模型（Ｌｉｎｅａｒ Ｓｔａｔｅ Ｓｐａｃｅ Ｍｏｄｉｌ－ＬＳＳＭ）,将ＣｙｇＸ－１的功率谱分解为ＬＳＳＭ产生的模型功率谱和剩余功率谱两部分。集中分析剩余功率谱,结果显示,ＣｙｇＸ－１在低／硬 态、转换态和高／软态三种状态的剩余功率谱有着不同的结构特征。其中高／软态和低／硬 态的剩余功率谱存在一个宽峰结构,中心频率分别为～８Ｈz和～５Ｈz,低／硬 态的剩余功率谱在～０．０７Ｈz达到极大  相似文献   

2.
运用自回归功率普研究Ｃｙｇ Ｘ－１ Ｘ辐射的频谱特征,结果显示Ｃｙｇ Ｘ－１转换态和高／软态时变频谱的连续成分,可以统一由有截断的幂律的成分描述,转换态存在小地３ＨＺ的宽峰结构及准周期振荡（ＱＰＯ）成分（４－１２ＨＺ）,而高／软态完全可由截断幂律普描述,不存在显著的ＱＰＯ。截断频率在各态相相当,在不同态的演化与平流为主的吸积流模型（ＡＤＡＦ（预期的情形一致。本文结果表明,自回归功率 研究Ｘ射线双  相似文献   

3.
分析ＲＸＴＥ卫星ＰＣＡ探测器对ＣｙｇＸ－１的观测数据,得到了其处于高态及高低高转换时的Ｘ射线短时标爆发（Ｓｈｏｔ）结构。在所观测到的三种态中是不对称的,并且不同的状态中Ｓｈｏｔ的结构有明显差异。Ｓｈｏｔ前后沿可分别由双指数函数近似拟合。Ｓｈｏｔ中的快时变过程是由慢的上升前沿和快的下降后沿构成。在所观测态中Ｓｈｏｔ平均宽度约为０．１１秒（ＦＷＨＭ）,比低态时的宽度窄。同一状态中高能段的Ｓｈｏｔ宽度较  相似文献   

4.
分析ＲＸＴＥ卫星ＰＣＡ探测器对ＣｙｇＸ－１的观测数据,得到了其处于高态及高低态转换时的Ｘ射线短时标爆发（Ｓｈｏｔ）结构．在所观测到的三种态中是不对称的,并且不同的状态中Ｓｈｏｔ的结构有明显差异．Ｓｈｏｔ前后沿可分别由双指数函数近似拟合．Ｓｈｏｔ中的快时变过程是由慢的上升前沿和快的下降后沿构成．在所观测态中Ｓｈｏｔ平均宽度约为０．１１秒（ＦＷＨＭ）,比低态时的宽度窄．同一状态中高能段的Ｓｈｏｔ宽度较低能段窄,且更加不对称．转换态的硬度在Ｓｈｏｔ峰前有明显下降,之后迅速上升,Ｓｈｏｔ期间的平均硬度低于非Ｓｈｏｔ期平均值;而高态时峰前硬度没有明显下降,Ｓｈｏｔ期间的平均硬度高于非Ｓｈｏｔ期间的平均值．本文还就Ｓｈｏｔ的产生机制进行了讨论．  相似文献   

5.
谢光中  Brink.  W 《天体物理学报》1997,17(3):323-326
利用ＲＯＳＡＴ－ＶＬＡ方法筛选，从ＲＯＰＳＡＴ Ｘ射线源中选出了一批新的ＢＬ Ｌａｃ天体和类星体的候选体。１９９６年１２月８日至１７日，利用北京天文台２．１６ｍ望远镜和新从美国引进的ＯＭＲ摄谱仪，对这批新候选体进行了光谱认证。经ＳＵＮ工作站处理，又发现了５个新的Ｘ选ＢＬ Ｌａｃ天体。  相似文献   

6.
通过分析１９９７年２月２７日和３月１日坚天座座Ｘ－１的两次空间数据观测。发现千赫兹ＱＰＯ频率同Ｘ射线能谱有一定相关,其和赤类似于另一个Ｘ射线同源４Ｕ１６０５－５２,讨论了分析结果对了解吸积及ＱＰＯ产生过程的意义。  相似文献   

7.
本文给出利用中国、意大利、南非射电望远镜对一个近赤道源样本在５ＧＨｚ频率上进行ＭＫ２ＶＬＢＩ普测中１０颗弱源的相关流量和其中部分源用ＨａｒｔＲＡＯ望远镜观测的总流量值，作为进一步的ＭＫ３或ＶＬＢＡ记录系统的ＶＬＢＩ观测依据．  相似文献   

8.
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   

9.
朱镇熹  杭恒荣 《天文学报》1999,40(3):247-255
在１９９５ 年至１９９７ 年,用２ ．１６ 米望远镜,５０?／ｍ ｍ 色散观测了仙后座１９９５ 新星的光谱．１９９５ 年的光谱以Ｆｅ Ⅱ及Ｈ Ⅰ的发射线为主要特征,所有发射线呈ＰＣｙｇ 轮廓,１９９６ 年光谱主要是Ｈ Ⅰ及Ｈｅ Ⅰ的发射,１９９７ 年光谱呈现很强的［Ｆｅ Ｘ］ 、［Ｆｅ ＶⅡ］ 、［Ｏ Ⅲ］ 发射,表明新星已进入星云阶段．以观测谱的连续谱估算了抛射物质的有效温度,算得１９９５ 年１０ 月１４ 日温度为２１３００Ｋ、１９９６ 年１０ 月２６ 日为９７００Ｋ、１９９７ 年１２ 月１６ 日为１０２００Ｋ．以测量谱线的流量估算抛射物质总质量约４ ．７ ×１０ － ５ Ｍ⊙,氦的丰度为ＮＨｅ／ＮＨ＝ ０ ．０４７ ．  相似文献   

10.
CygX-1 X辐射的功率谱   总被引：1，自引：1，他引：0  
运用自回归功率谱研究CygX－1X辐射的频谱特征,结果显示CygX－1转换态和高／软态时变频谱的连续成分,可以统一由有截断的幂律加噪声成分描述,转换态存在小于3Hz的宽峰结构及准周期振荡（QPO）成分（4－12Hz）,而高／软态完全可由截断幂律谱描述,不存在显著的QPO．截断频率在各态都相当稳定,在不同态的演化与平流为主的吸积流模型（ADAF）预期的情形一致．本文结果表明,自回归功率港分析是研究X射线双星光变特征的一个有效的方法．  相似文献   

11.
利用“慧眼”(Hard X-ray Modulation Telescope, Insight-HXMT)卫星在2017年9月对黑洞候选体MAXI J1535-571的观测数据,研究了该源在爆发期内的时变现象.当源处于不同的爆发谱态时,功率密度谱的谱型存在明显差异.在硬中间态,有明显的限带噪声(band-limited noise)成分和QPO (Quasi-Periodic Oscillation)成分.分析结果表明:低频限带噪声的特征频率随能量的变化呈现正相关,即软能段光子的特征频率小于硬能段光子的特征频率. 0.1–0.5 Hz频率区间的限带噪声RMS (Root Mean Square)谱在硬中间态和软中间态均出现峰值,且在高能端存在差异,可能是主导噪声RMS的能谱成分占比不同.当谱态由硬中间态过渡到软中间态时, C型QPO的RMS谱保持相似趋势,但限带噪声RMS谱存在谱态依赖现象,暗示着噪声和QPO有不同的起源机制.  相似文献   

12.
We report the results of a systematic timing analysis of RXTE observations of GRS 1915+105 when the source was in its variability class θ, characterized by alternating soft and hard states on a time-scale of a few hundred seconds. The aim was to examine the high-frequency part of the power spectrum in order to confirm the hectohertz quasi-periodic oscillations (QPO) previously reported from observations from mixed variability behaviours. During the hard intervals (corresponding to state C in the classification of Belloni et al.), we find a significant QPO at a frequency of ∼170 Hz, although much broader (Q∼2) than previously reported. No other significant peak is observed at frequencies >30 Hz. A time-resolved spectral analysis of selected observations shows that the hard intervals from class θ show a stronger and steeper  (Γ= 2.8–3.0)  power-law component than hard intervals from other classes. We discuss these results in the framework of hectohertz QPOs reported from GRS 1915+105 and other black hole binaries.  相似文献   

13.
Among the variability behaviours exhibited by neutron star systems are the so-called 'horizontal branch oscillations' (HBO, with frequencies ≈50 Hz), the 'lower-frequency kHz quasi-periodic oscillation' (QPO) and the 'upper-frequency kHz QPO', with the latter two features being separated in frequency by an amount comparable to, but varying slightly from, the suspected spin-frequency of the neutron star. Recently, Psaltis, Belloni & van der Klis have suggested that there exists a correlation between these three frequencies that, when certain identifications of variability features are made, even encompasses black hole sources. We consider this hypothesis by reanalysing a set of GX 339−4 observations. The power spectral density (PSD) constructed from a composite of seven separate, but very similar, observations shows evidence for three broad peaks in the PSD. If the peak frequencies of these features are identified with QPO, then their frequencies approximately fit the correlations suggested by Psaltis, Belloni, & van der Klis. We also reanalyse a Cyg X-1 observation and show that the suggested QPO correlation may also hold, but that complications arise when the QPOs (which, in reality, are fairly broad features) are considered as a function of energy band. These fits suggest the existence of at least three separate, independent physical processes in the accretion flow, a hypothesis that is also supported by consideration of the Fourier frequency-dependent time lags and coherence function between variability in different energy bands. If these variability features have a common origin in neutron star and black hole systems, then 'beat frequency models' of kHz QPO in neutron star systems are called into question.  相似文献   

14.
The observations of the black hole binary Cygnus X-l were made in the energy band of 20–100keV with a balloon-borne Xenon-filled multiwire proportional counter telescope on 5th April 1992. Timing analysis of the data revealed the presence of Quasi-Periodic Oscillations (QPO) in the hard X-ray emission from the source. The QPO feature in the power density spectrum is broad with a peak at a frequency of 0.06 Hz. This result is compared with similar reports of QPOs in Cyg X-l in soft and hard X-rays. Short time scale random intensity variations in the X-ray light curve are described with a shot noise model.  相似文献   

15.
The LE is the low energy telescope that is carried on Insight-HXMT.It uses swept charge devices(SCDs)to detect soft X-ray photons.LE’s time response is caused by the structure of the SCDs.With theoretical analysis and Monte Carlo simulations we discuss the influence of LE time response(LTR)on the timing analysis from three aspects:the power spectral density,the pulse profile and the time lag.After the LTR,the value of power spectral density monotonously decreases with the increasing frequency.The power spectral density of a sinusoidal signal reduces by a half at frequency 536 Hz.The corresponding frequency for quasi-periodic oscillation(QPO)signals is 458 Hz.The root mean square(RMS)of QPOs holds a similar behaviour.After the LTR,the centroid frequency and full width at half maxima(FWHM)of QPOs signals do not change.The LTR reduces the RMS of pulse profiles and shifts the pulse phase.In the time domain,the LTR only reduces the peak value of the cross-correlation function while it does not change the peak position;thus it will not affect the result of the time lag.When considering the time lag obtained from two instruments and one among them is LE,a 1.18 ms lag is expected caused by the LTR.The time lag calculated in the frequency domain is the same as that in the time domain.  相似文献   

16.
Previous observations with the Rossi X-ray Timing Explorer ( RXTE ) have suggested that the power spectral density (PSD) of NGC 3783 flattens to a slope near zero at low frequencies, in a similar manner to that of Galactic black hole X-ray binary systems (GBHs) in the 'hard' state. The low radio flux emitted by this object, however, is inconsistent with a hard state interpretation. The accretion rate of NGC 3783 (∼7 per cent of the Eddington rate) is similar to that of other active galactic nuclei (AGN) with 'soft'-state PSDs and higher than that at which the GBH Cyg X-1, with which AGN are often compared, changes between 'hard' and 'soft' states (∼2 per cent of the Eddington rate). If NGC 3783 really does have a 'hard'-state PSD, it would be quite unusual and would indicate that AGN and GBHs are not quite as similar as we currently believe. Here we present an improved X-ray PSD of NGC 3783, spanning from ∼10−8 to ∼10−3 Hz, based on considerably extended (5.5 yr) RXTE observations combined with two orbits of continuous observation by XMM–Newton . We show that this PSD is, in fact, well fitted by a 'soft' state model which has only one break, at high frequencies. Although a 'hard'-state model can also fit the data, the improvement in fit by adding a second break at low frequency is not significant. Thus NGC 3783 is not unusual. These results leave Arakelian 564 as the only AGN which shows a second break at low frequencies, although in that case the very high accretion rate implies a 'very high', rather than 'hard' state PSD. The break frequency found in NGC 3783 is consistent with the expectation based on comparisons with other AGN and GBHs, given its black hole mass and accretion rate.  相似文献   

17.
We have produced the colour–colour diagram of all the observations of 4U 1728–34 available in the Rossi X-ray Timing Explorer public archive (from 1996 to 2002) and found observations filling in a previously reported 'gap' between the island and the banana X-ray states. We have made timing analysis of these gap observations and found, in one observation, two simultaneous kHz quasi-periodic oscillations (QPOs). The timing parameters of these kHz QPOs fit in the overall trend of the source. The 'lower' kHz QPO has a centroid frequency of ∼308 Hz. This is the lowest 'lower' kHz QPO frequency ever observed in 4U 1728–34. The peak frequency separation between the 'upper' and the 'lower' kHz QPO is  Δν= 274 ± 11 Hz  , significantly smaller than the constant value of  Δν∼ 350 Hz  found when the 'lower' kHz QPO frequency is between ∼500 and 800 Hz. This is the first indication in this source for a significant decrease of kHz QPO peak separation towards low frequencies. We compare the result briefly to theoretical models for kHz QPO production.  相似文献   

18.
We have monitored the atoll-type neutron star low-mass X-ray binary 4U 1636−53 with the Rossi X-ray Timing Explorer ( RXTE ) for more than 1.5 yr. Our campaign consisted of short (∼2 ks) pointings separated by 2 d, regularly monitoring the spectral and timing properties of the source. During the campaign we observed a clear long-term oscillation with a period of ∼30–40 d, already seen in the light curves from the RXTE All-Sky Monitor, which corresponded to regular transitions between the hard (island) and soft (banana) states. We detected kilohertz (kHz) quasi-periodic oscillations (QPOs) in about a third of the observations, most of which were in the soft (banana) state. The distribution of the frequencies of the peak identified as the lower kHz QPO is found to be different from that previously observed in an independent data set. This suggests that the kHz QPOs in the system shows no intrinsically preferred frequency.  相似文献   

19.
XMM–Newton X-ray spectra of the hard state black hole X-ray binaries (BHXRBs) SWIFT J1753.5−0127 and GX 339−4 show evidence for accretion disc blackbody emission, in addition to hard power laws. The soft and hard band power spectral densities (PSDs) of these sources demonstrate variability over a wide range of time-scales. However, on time-scales of tens of seconds, corresponding to the putative low-frequency Lorentzian in the PSD, there is additional power in the soft band. To interpret this behaviour, we introduce a new spectral analysis technique, the 'covariance spectrum', to disentangle the contribution of the X-ray spectral components to variations on different time-scales. We use this technique to show that the disc blackbody component varies on all time-scales, but varies more, relative to the power law, on longer time-scales. This behaviour explains the additional long-term variability seen in the soft band. Comparison of the blackbody and iron line normalizations seen in the covariance spectra in GX 339−4 implies that the short-term blackbody variations are driven by thermal reprocessing of the power-law continuum absorbed by the disc. However, since the amplitude of variable reflection is the same on long and short time-scales, we rule out reprocessing as the cause of the enhanced disc variability on long time-scales. Therefore, we conclude that the long time-scale blackbody variations are caused by instabilities in the disc itself, in contrast to the stable discs seen in BHXRB soft states. Our results provide the first observational evidence that the low-frequency Lorentzian feature present in the PSD is produced by the accretion disc.  相似文献   

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