XTE J1550-564 2001年“迷你爆发”的X射线能谱研究

黑洞X射线暂现源的迷你爆发是一类峰值光度较低、持续时间较短的爆发.由于观测数据较少,其物理机制仍不清楚.利用RXTE (Rossi X-ray Timing Explorer)卫星从2001年1月28日到3月14日的数据,研究了黑洞X射线暂现源XTE J1550–564 2001年迷你爆发的X射线能谱特性.发现在本次迷你爆发中, XTE J1550–564的X射线能谱可以用幂律谱很好地拟合.整个爆发的硬度强度图不是标准的q型,而是一直保持在最右侧.此外,还分析了此次爆发谱指数Γ与未吸收的2–10 keV能段的X射线流量F_(2–10 keV)的相关性,发现Γ-F_(2–10 keV)呈反相关关系,且谱指数Γ∈[1.35, 1.72].上述结果表明2001年这次爆发一直处于低/硬态,它的X射线辐射主要来自于辐射低效的吸积模式,如ADAF(Advection-Dominated Accretion Flow).     

窄线赛弗特Ⅰ型星系中可能具有吸积盘热辐射起源的软X射线超

理论上,低质量高吸积率活动星系核的标准吸积盘黑体热辐射有可能形成软X射线波段的超出。然而,活动星系核的软X射线超温度为0.1 keV左右,显著高于标准吸积盘理论预言的最高有效温度。只有Yuan等人在2010年报道的RX J1633+4718是一个例外,其软超温度为32.5_-6.0^+8.0 eV,显著小于0.1 keV,并与吸积盘理论预言的温度相符;此外,其光度也符合吸积盘的理论预期。因此该软X射线超很可能起源于吸积盘的热辐射。这一类源对于吸积盘理论和软X射线超的研究都有重要意义。文中使用ROSATPSPC数据,在所有已知的窄线赛弗特Ⅰ型星系（Narrow Line SeyfertⅠgalaxies,NLSIs）中寻找类似于RX J1633+4718的源,即软X射线超可能起源于吸积盘热辐射的源。分析了150个源的245条光谱,其中58个源的90条光谱具有显著的软X射线超。样本中软X射线超温度分布的平均值T_soft为0.10keV,标准偏差为0.03 keV。除了RX J1633+4718外,只有3个源的软X射线超温度小于60 eV,而且温度接近吸积盘最高温度。这个结果表明,类似于RX J1633+4718的具有低温软X射线超的源很稀少。最后,在具有黑洞质量估计的26个源中,软超温度与黑洞质量M_BH、爱丁顿比L/LEdd及预期吸积盘最高温度T_max都没有明显的关联性,与前人的结果一致。     

部分遮蔽类星体SDSS J151653.22+190048.2的紫外波段中等宽度发射线起源

类星体SDSS J151653.22+190048.2 (简称J1516+1900)在紫外-光学-近红外波段展现出奇特的光谱性质:其光学Hα、Hβ和近红外的Paα、Paβ等发射线的半高全宽(full width at half maximum intensity, FWHM)均超过5000 km/s,等值宽度接近类星体平均值;而紫外波段光谱的常见发射线Lyβ、OVI、Lyα、NV、Si IV和CIV等,由FWHM1700 km/s的中等宽度成分主导.这种现象很可能是由于紫外发射线的宽线成分经尘埃消光,强度严重削弱,从而使得中等宽度成分凸显出来;在光学和近红外波段,尘埃消光减弱,发射线由宽线成分主导,潜在的中等宽度成分不容易被看到.根据中等宽度成分的线宽和J1516+1900中央超大质量黑洞的质量MBH5.75×108M⊙,在维里化假设下,估计中等宽度发射区到中央黑洞的距离约为1.6 pc.另一方面,利用J1516+1900丰富的观测谱线,结合光致电离模型计算,可以限定J1516+1900的中等宽度发射线区气体密度1012cm-3、电离参数10-0.65.据此估计该发射线区到中心黑洞距离0.016 pc,只有维里化距离的1%.这一矛盾结果预示着中等宽度发射区可能具有较为复杂的物理结构,未来需要观测更多类似J1516+1900的部分遮蔽类星体并进行系统的分类和研究.     

光学相机FOC对黑洞双星高时间分辨测光性能研究

黑洞暂现双星MAXI J1820+070于2018年3月的明亮爆发为研究光学快速测光能力提供了重要机遇. 以快速光学相机(Fast Optical Camera, FOC)为终端设备分别在2018年4月22日、5月26日和8月31日(UTC)使用云南天文台丽江观测站2.4m望远镜对爆发中的黑洞双星MAXI J1820+070进行了亚秒时标的测光观测. 通过观测数据分析, 研究了相机的快速测光性能.对全帧和1/4帧两种观测模式的帧间间隔(frame time), 测得平均帧间间隔为(22.866 pm 0.679)ms和(5.868 pm 0.169)ms. 通过视场中多颗明亮参考源校准,提取了观测对象和参考源的光变曲线, 获得了光变曲线的傅里叶功率谱, 区分了观测对象本征光变和仪器或望远镜等观测因素带来的非本征光变, 成功探测到目标黑洞双星MAXI J1820+070中的光学波段低频准周期振荡信号, 并判别了观测中来自仪器设备或与观测条件相关的时变信号. 这成功验证了相机高速稳定的测光性能和对短至5ms时标光变信号的探测能力.     

基于混合模型的疏散星团视向速度和金属丰度研究

疏散星团是研究星族和银河系形成与演化的理想示踪体。基于LAMOST DR7低分辨率光谱,在视向速度和金属丰度两维空间上,构建包含团星和场星的混合模型：以二维正高斯模型来描述团星的分布,以星团天区周围的恒星来构建场星的分布模型。同时,在模型中考虑了观测误差的影响。对3个具有丰富光谱数据的典型疏散星团进行了拟合。年轻星团Melotte 22和中年星团NGC 2281可以较好地约束其视向速度的内禀弥散,分别为：1.47_-1.18^+0.95km·s^-1和2.05_-1.18^+1.39km·s^-1,而年老星团NGC 2682只能给出速度弥散的上限约为0.96 km·s^-1。Melotte22、NGC 2281和NGC 2682的金属丰度内禀弥散分别为：0.170_-0.009^+0.012dex,(0.108±0.012) dex和(0.050±0.005) dex,都明显大于金属丰度的观测误差(约0.02...     

缘于任意自旋场的Vaidya黑洞的熵(英文)

用在brick模型基础上发展起来的membrane模型 ,计算了缘于任意自旋场的非静态黑洞———Vaidya黑洞的自由能和熵。结果表明 ,玻色子场 (自旋s =1,2 )和费米子场 (自旋s =1/2 )的熵都恰好与黑洞的视界面积成正比 ,这与静态和稳态的情况相同。而且 ,玻色子和费米子场的熵具有相同的形式 ,二者相差一个系数     

恒星级双黑洞自旋研究进展

自2015年以来,人们已经探测到93例恒星级双黑洞并合引力波事件,测量了双黑洞质量、自旋和距离等参数,并获得了其统计分布。不同双黑洞起源机制产生的双黑洞性质分布,特别是自旋分布,会显著不同,其可用来限制双黑洞起源。简单回顾了双星演化和动力学相互作用等双黑洞形成机制及自旋来源;综述了利用自旋限制双黑洞起源的一般方法和常见模型,以及利用LIGO/Virgo引力波数据取得的相关进展,并对未来发展前景进行了展望。     

粘滞对黑洞吸积盘的截断的影响

采用吸积盘-冕模型研究了粘滞对黑洞X射线双星和低光度活动星系核(LLAGN)中吸积盘的截断以及黑洞X射线双星中高低态转变的影响.以前的分析表明,冕的结构对粘滞的大小非常敏感.因此详细计算了一系列粘滞系数情况下冕的结构.为了便于与观测比较,将数值计算结果进行解析拟合得到最大蒸发率和粘滞系数a的关系,M/MEDD≈1.08a3.35;截断半径和粘滞系数的关系,R/Rs≈36.11a-1.94.这些结果可以用来解释光谱态的高低态的转换和截断半径的变化.并将这些结果应用到几个黑洞X射线双星XTE J118 480,GX 339-4,以及活动星系核NGC 4636中.     

黑洞吸积理论及其天体物理学应用的近期发展(Ⅱ)

黑洞吸积理论是天体物理学的一个基础理论,是认识许多高能天体系统如活动星系核、黑洞X射线双星,以及伽马暴等的重要物理基础.该文评述近年来黑洞吸积理论尤其是径移主导吸积流模型(advection-dominated accretion flow)及其变种的主要发展,并介绍该理论在银河系中心、低光度活动星系核、黑洞X射线双星等方面的应用.共分为两篇,该文是第2篇,内容是关于黑洞热吸积流理论在低光度活动星系核以及黑洞X射线双星方面的应用.     

Blazar黑洞质量

与吸积率和爱丁顿吸积率的比率一道,黑洞质量也是活动星系核的一个基本参数。我们采用谢光中等的新方法去估计了21个blazar样本的黑洞质量(MH),同时运用了MBH-σ相关分析方法来估计同一个blazar样本的黑洞质量(Mσ),通过对两种不同方法所得样本黑洞质量的比较,我们发现(1)MH系统的小于Mσ,但是对于大多数blazar样本来说Mσ和MH之间的差别很小;(2)在Mσ和MH之间存在着一个有意义的相关性,相关系数为r=0.832,p≤1.0×10-4。以上述的这些性质和活动星系核标准模型为基础,我们证明了这两种方法所得的黑洞质量Mσ和MH之间的系统差异是因为Mσ描述的是宽发射线区(r≤rb)的黑洞质量,而MH描述的是黑洞周围在最内层轨道附近的连续发射区的质量。这就是说Mσ应该是被过度估计了。由Mσ和中心黑洞质量MH*的关系,我们再次计算中心黑洞质量MH*,并且发现中心黑洞质量MH*和MH几乎是相同的。     

On the formation and evolution of black hole binaries

We present the results of a systematic study of the formation and evolution of binaries containing black holes and normal-star companions with a wide range of masses. We first reexamine the standard formation scenario for close black hole binaries, where the progenitor system, a binary with at least one massive component, experienced a common-envelope phase and where the spiral-in of the companion in the envelope of the massive star caused the ejection of the envelope. We estimate the formation rates for different companion masses and different assumptions about the common-envelope structure and other model parameters. We find that black hole binaries with intermediate- and high-mass secondaries can form for a wide range of assumptions, while black hole binaries with low-mass secondaries can only form with apparently unrealistic assumptions (in agreement with previous studies).
We then present detailed binary evolution sequences for black hole binaries with secondaries of 2 to 17 M_⊙ and demonstrate that in these systems the black hole can accrete appreciably even if accretion is Eddington-limited (up to 7 M_⊙ for an initial black hole mass of 10 M_⊙) and that the black holes can be spun up significantly in the process. We discuss the implications of these calculations for well-studied black hole binaries (in particular GRS 1915+105) and ultraluminous X-ray sources of which GRS 1915+105 appears to represent a typical Galactic counterpart. We also present a detailed evolutionary model for Cygnus X-1, a massive black hole binary, which suggests that at present the system is most likely in a wind mass-transfer phase following an earlier Roche-lobe overflow phase. Finally, we discuss how some of the assumptions in the standard model could be relaxed to allow the formation of low-mass, short-period black hole binaries, which appear to be very abundant in nature.     

Hard X-ray states and radio emission in GRS 1915+105

We compare simultaneous Ryle Telescope radio and Rossi X-Ray Timing Explorer X-ray observations of the galactic microquasar GRS 1915+105, using the classification of the X-ray behaviour in terms of three states as previously established. We find a strong (one-to-one) relation between radio oscillation events and series of spectrally hard states in the X-ray light curves, if the hard states are longer than ∼100 s and are 'well separated' from each other. In all other cases the source shows either low-level or high-level radio emission, but no radio oscillation events. During intervals when the source stays in the hard spectral state for periods of days to months, the radio behaviour is quite different; during some of these intervals a quasi-continuous jet is formed with an almost flat synchrotron spectrum extending to at least the near-infrared. Based on the similarities between the oscillation profiles at different wavelengths, we suggest a scenario which can explain most of the complex X-ray:radio behaviour of GRS 1915+105. We compare this behaviour with that of other black hole sources, and challenge previous reports of a relation between spectrally soft X-ray states and the radio emission.     

GRS 1915+105: the distance, radiative processes and energy-dependent variability

We present an exhaustive analysis of five broad-band observations of GRS 1915+105 in two variability states, χ and ω, observed simultaneously by the Proportional Counter Array (PCA) and High-Energy X-ray Timing Experiment (HEXTE) detectors aboard the Rossi X-ray Timing Explorer , and the Oriented Scintillation Spectrometer Experiment (OSSE) detector aboard the Compton Gamma-ray Observatory . We find all the spectra well fitted by Comptonization of disc blackbody photons, with very strong evidence for the presence of a non-thermal electron component in the Comptonizing plasma. Both the energy and the power spectra in the χ state are typical of the very high/intermediate state of black hole binaries. The spectrum of the ω state is characterized by a strong blackbody component Comptonized by thermal electrons and a weak non-thermal tail. We then calculate rms spectra (fractional variability as functions of energy) for the PCA data. We accurately model the rms spectra by coherent superposition of variability in the components implied by the spectral fits, namely a less variable blackbody and more variable Comptonization. The latter dominates at high energies, resulting in a flattening of the rms at high energies in most of the data. This is also the case for the spectra of the quasi-periodic oscillations present in the χ state. Then, some of our data require a radial dependence of the rms of the disc blackbody. We also study the distance to the source, and find   d ≃ 11 kpc  as the most likely value, contrary to a recent claim of a much lower value.     

On the source of quasi-periodic oscillations of the black hole candidate GRS 1915+105: some new observations and their interpretation

A few classes of the light curve of the black hole candidate GRS 1915+105 have been analysed in detail. We discover that unlike the previous findings, quasi-periodic oscillations (QPOs) occasionally occur even in the so-called 'On' or softer states. Such findings may require a revision of the accretion/wind scenario of the black hole candidates. We conjecture that considerable winds that are produced in 'Off' states cool down as a result of Comptonization and fall back to the disc, creating an excess accretion rate and producing the so-called 'On' state. After the drainage of the excess matter, the disc goes back to the 'Off' state. Our findings strengthen the shock oscillation model for QPOs.     

Infrared synchrotron oscillations in GRS 1915+105

We report simultaneous observations of the black hole candidate X-ray transient GRS 1915+105 in the infrared (IR) at K and in the radio at 2 cm. Oscillations of period 26 min were observed in both wavebands, having (dereddened) peak–peak amplitudes of about 40 mJy and with the IR leading the radio by 7 min, or perhaps by 33 or 59 min. A synchrotron origin for the oscillations continues to seem very likely. We consider a range of problems raised by these observations, and briefly discuss the applicability of expanding-synchrotron source or conical jet models to the oscillations. Comparing simplistic estimates of the ejecta mass to the missing inner disc mass in the model of Belloni et al., we find that a significant fraction of the inner disc may be ejected during the oscillations.     

Effects of magnetic coupling on radiation from accretion disc around a Kerr black hole

The effects of magnetic coupling (MC) process on the inner edge of the disc are discussed in detail. It is shown that the inner edge can deviate from the innermost stable circular orbit (ISCO) due to the magnetic transfer of energy and angular momentum between a Kerr black hole (BH) and its surrounding accretion disc. It turns out that the inner edge could move inwards and outwards for the BH spin a _* being greater and less than 0.3594, respectively. The MC effects on disc radiation are discussed based on the displaced inner edge. A very steep emissivity can be provided by the MC process, which is consistent with the observation of MCG-6-30-15. In addition, the BH spins of GRO J1655−40 and GRS 1915+105 are detected by X-ray continuum fitting based on this model.     

Observational aspects of outbursting black hole sources: Evolution of spectro-temporal features and X-ray variability

We report on our attempt to understand the outbursting profile of Galactic Black Hole sources, keeping in mind the evolution of temporal and spectral features during the outburst. We present results of evolution of quasi-periodic oscillations, spectral states and possible connection with jet ejections during the outburst phase. Further, we attempt to connect the observed X-ray variabilities (i.e., ‘class’/‘structured’ variabilities, similar to GRS 1915+105) with spectral states of black hole sources. Towards these studies, we consider three black hole sources that have undergone single (XTE J1859+226), a few (IGR J17091-3624) and many (GX 339-4) outbursts since the start of RXTE era. Finally, we model the broadband energy spectra (3–150 keV) of different spectral states using RXTE and NuSTAR observations. Results are discussed in the context of two-component advective flow model, while constraining the mass of the three black hole sources.     

RE J1034+396: the origin of the soft X-ray excess and quasi-periodic oscillation

The X-ray quasi-periodic oscillation (QPO) seen in RE J1034+396 is so far unique amongst active galactic nuclei (AGN). Here, we look at another unique feature of RE J1034+396, namely its huge soft X-ray excess, to see if this is related in any way to the detection of the QPO. We show that all potential models considered for the soft energy excess can fit the 0.3–10 keV X-ray spectrum, but the energy dependence of the rapid variability (which is dominated by the QPO) strongly supports a spectral decomposition where the soft excess is from low-temperature Comptonization of the disc emission and remains mostly constant, while the rapid variability is produced by the power-law tail changing in normalization. The presence of the QPO in the tail rather than in the disc is a common feature in black hole binaries (BHBs), but low-temperature Comptonization of the disc spectrum is not generally seen in these systems. The main exception to this is GRS 1915+105, the only BHB which routinely shows super-Eddington luminosities. We speculate that the super-Eddington accretion rates lead to a change in disc structure, and that this also triggers the X-ray QPO.     

Evolution of black hole intermediate-mass X-ray binaries: the influence of a circumbinary disc

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.     

Multiwavelength monitoring of GRS 1915+105

Since its discovery in 1992, the superluminal X-ray transient GRS 1915+105 has been extensively observed in an attempt to understand its behaviour. We present here first results from a multiwavelength campaign undertaken from 1996 July to September. This study includes X-ray data from the RXTE All Sky Monitor and BATSE , two-frequency data from the Nançay radio telescope, and infrared photometry from the 1.8-m Perkins telescope at Lowell Observatory. The first long-term, well-sampled infrared light curve of GRS 1915+105 is presented herein; it is consistent with the interpretation of this source as a long-period binary. We compare the various light curves, searching for correlations in the behaviour of the source at differing wavelengths and for possible periodicities.