银河核球X射线源GX9＋1的振荡现象

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。     

银河系薄盘形成对核球的动力学影响

近期的研究认为,银河系核球是侧面看到的棒,由原初盘演化而来,并非由星系并合形成。核球形成的时间在银河系演化早期,而后续来自晕的气体吸积在银河系薄盘处形成的新恒星对核球是否会造成比较大的动力学影响,仍是一个重要的问题。通过在盘上添加新粒子的方法模拟薄盘的形成,发现在大多数情况下薄盘形成并没有对核球的平均速度、速度弥散、棒的强度和旋转速度产生明显的影响;但是在恒星形成率特别大或者新形成的恒星特别接近棒的时候,核球区的恒星速度弥散、棒的强度和旋转速度会同时增大。薄盘恒星在加入1～2 Ga后,在经度3°～10°处其视向速度分布有可能存在类似APOGEE巡天中观测到的高速峰。高速峰的形成时间与恒星添加位置有关,添加位置离棒越近,高速峰越早形成。     

银河系核球中垂向金属丰度梯度的一种可能的动力学起源机制

研究发现,即使在银河系长期缓慢演化的过程中,其核球中依然可能存在垂直的金属丰度梯度。该结果反驳了早期研究中认为的银河系核球中长期缓慢演化的过程会消除任何存在的化学丰度梯度的观点。通过使用一个模拟银河系薄盘的多体数值模拟模型得出该研究结果,该模型能自洽地通过盘的棒不稳定性和屈曲不稳定性形成一个盒状/花生状的核球,并结合化学-动力学模型,分析银河系核球中化学成分的演化。在该演化模型中设定了一个初始的径向金属丰度梯度(-0.3 dex/kpc),通过长期缓慢的演化过程,其核球部分呈现出与观测相符的垂直金属丰度梯度。对此一种可能的解释是,星系盘的金属丰度分布在长期缓慢演化的过程中经历了“两步”演化过程,首先盘星系初始半径较大的贫金属粒子在径向混合的过程中产生了更大的径向速度弥散,然后由于核球的屈曲不稳定性演化,垂向速度弥散最终会保持与径向速度弥散的一定比值(约0.8)。这个机制导致贫金属粒子在演化过程中能占据更大的垂向范围,从而形成核球的垂直金属丰度梯度。银河系核球动力学模型通过简单的化学-动力学过程揭示的核球金属丰度演化机制,应在包含更复杂的核球演化机制的模型中同样存在。此外,还通过化学动力...     

应用X射线源的航天器姿态测量

在介绍X射线源和X射线探测器、准直器的基础上,重点描述了应用X射线源测量航天器姿态参数的原理和方法。对X射线星扫描仪的结构、扫描观测X射线源方法和矩形准直器响应函数等做了介绍,较详细地论述了应用单准直器X射线星扫描仪和差分准直器X射线星扫描仪确定航天器姿态参数的测量模型,并进行了二者间的比较和分析。简单讨论了X射线星扫描仪测量建模和应用测量模型拟合航天器姿态参数的算法问题。最后,对采用编码孔径系统确定航天器姿态参数的方法做了概括性介绍。     

脉冲星PSR1951＋32的X射线脉冲辐射

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...     

ROSAT X射线源1057＋4316被证认为一个z＝0．32的类星体

根据北京天文台２．１６ｍ望远镜的有缝光谱观测，证认出位于１０ｈ５７ｍ４８．５ｓ＋４３°１６′１３″（１９５０．０）的一个ＲＯＳＡＴＸ射线源是一个ｚ＝０．３２的类星体。     

8个ROSAT X射线源和5G射电源被证认为类星体

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。     

准周期振荡(QPO)天体GX5-1的双分支谱的唯象分析

本文对小质量X射线双星的准周期振荡的差频模型做了修正和补充。修正的要点是:要考虑柱吸积过程中的粘滞阻尼。由此即可成功地解释QPO天体GX5-1的双分支谱特性。     

Oscillation phenomena in the galactic bulge X-ray source GX 9 + 1

Analyzing the observational data of the galactic bulge X-ray source GX 9 + 1 we found oscillations on the scale of hundreds of seconds to be present. This result should help our understanding of the accretion properties and orbital motion of this low-mass, X-ray binary.     

The role of the Galactic Halo and the Single Source in the formation of the cosmic ray anisotropy

The existence of the cosmic ray Halo in our Galaxy has been discussed for more than half a century. If it is real it could help to explain some puzzling features of the cosmic ray flux: its small radial gradient, nearly perfect isotropy and the low level of the fine structure in the energy spectra of the various particles. All these features could be understood if: (a) the Halo has a big size (b) cosmic rays in the Halo have a uniform spatial or radial distribution and (c) the cosmic ray density in the Halo is comparable or even higher than that in the Galactic Disk. The main topic of the paper concerns the present status of the anisotropy and a model for its formation. In our model the extremely small amplitude of the dipole anisotropy is due to the dilution of the anisotropy in the Disk by the dominating isotropic cosmic rays from the Halo. Some minor deviations from complete isotropy in the sub-PeV and PeV energy regions point out to the possible contribution of the Single Source with the phase of its first harmonic opposite to the phase produced by the Disk.     

A hard X-ray survey of the Galactic-Center region with the IBIS telescope of the INTEGRAL observatory: A catalog of sources

From August 23 through September 24, 2003, the INTEGRAL Observatory conducted a deep survey of the Galactic-Center region with a record-breaking sensitivity at energies above 20 keV. We have analyzed the images of the Galactic-Center region obtained with the ISGRI detector of the IBIS telescope (15–200 keV) and give a catalog of detected sources. We detected a total of 60 sources with fluxes above 1.5 mCrab, 44 and 3 of which were previously identified as binary systems of different classes in our Galaxy and as extragalactic objects, respectively. We discovered one new source.     

X-ray bursts from the source A1742-294 in the Galactic-center region

We present observations of the X-ray burster A1742-294 near the Galactic center with the ART-P telescope onboard the Granat observatory. The shape of its persistent spectra was described well by the model of bremsstrahlung from optically thin plasma, and it remained essentially unchanged over ～2.5 years of observations. We show that the mean interval between X-ray bursts from the source is several times shorter than assumed previously and that the burst profile itself depends on the flux during the burst. We analyze in detail the strong X-ray burst detected from this source on October 18, 1990, and construct the evolution curves of its luminosity and radiation temperature.     

Development of the hard X-ray imaging experiment timax: Laboratory images and first balloon flight

We present calibration results and laboratory images produced by the balloon-borne hard X-ray imaging telescope TIMAX. The images were produced with an²⁴¹Am radioactive source placed 45 m away from the detector plane, in the center of the field of view. It is shown that the mask 3-antimask imaging reconstruction process, when combined with flat-fielding techniques, is very effective at recovering signal-to-noise ratio lost due to systematic non-uniformity in the background measured by the 35 detectors. The experiment was launched in June 8th, 1993 from Birigüi, SP, Brazil, onboard a 186,000 m³ stratospheric balloon, and remained at an atmospheric depth of 2 g cm^–2su for 8 hours. Even though no scientific data were gathered in this first flight, we obtained valuable engineering data and could also calculate the sensitivity of the experiment based on the instrumental background spectrum at balloon altitudes. In the 60–70 keV energy band, the experiment can detect 3 sources at a level of 1.2 x 10^–4 photons cm^–2 s^–1 keV^–1 for an integration of 6 hours at 2.1 g cm^–2.     

Spectral variation in the X-ray pulsar GX 1+4 during a low-flux episode

The X-ray pulsar GX 1+4 was observed with the RXTE satellite for a total of 51 ks between 1996 July 19 and 21. During this period the flux decreased smoothly from an initial mean level of ≈6×10³⁶ erg s⁻¹ to a minimum of ≈4×10³⁵ erg s⁻¹ (2–60 keV, assuming a source distance of 10 kpc) before partially recovering towards the initial level at the end of the observation.
BATSE pulse timing measurements indicate that a torque reversal took place approximately 10 d after this observation. Both the mean pulse profile and the photon spectrum varied significantly. The observed variation in the source may provide important clues as to the mechanism of torque reversals.
The single best-fitting spectral model was based on a component originating from thermal photons with kT ₀≈1 keV Comptonized by a plasma of temperature kT ≈7 keV. Both the flux modulation with phase during the brightest interval and the evolution of the mean spectra over the course of the observation are consistent with variations in this model component; with, in addition, a doubling of the column density n _H contributing to the mean spectral change.
A strong flare of duration ≲50 s was observed during the interval of minimum flux, with the peak flux ≈20 times the mean level. Although beaming effects are likely to mask the true variation in M ˙ thought to give rise to the flare, the timing of a modest increase in flux prior to the flare is consistent with dual episodes of accretion resulting from successive orbits of a locally dense patch of matter in the accretion disc.     

Ultrahigh energy nuclei in the turbulent Galactic magnetic field

In this work we study how the turbulent component of the Galactic magnetic field (GMF) affects the propagation of ultrahigh energy heavy nuclei. We investigate first how the images of individual sources and of the supergalactic plane depend on the properties of the turbulent GMF. Then we present a quantitative study of the impact of the turbulent field on (de-)magnification of source fluxes, due to magnetic lensing effects. We also show that it is impossible to explain the Pierre Auger data assuming that all ultrahigh energy nuclei are coming from Cen A, even in the most favorable case of a strong, extended turbulent field in the Galactic halo.     

Optical identifications of five INTEGRAL hard X-ray sources in the Galactic plane

The results of optical identifications of five hard X-ray sources in the Galactic plane from the INTEGRAL all-sky survey are presented. The X-ray data on one source (IGR J20216+4359) are published for the first time. The optical observations were performed with the 1.5-m RTT-150 telescope (Turkish National Observatory, Antalya, Turkey) and the 6-m BTA telescope (Special Astrophysical Observatory, Nizhny Arkhyz, Russia). A blazar, three Seyfert galaxies, and a high-mass X-ray binary are among the identified sources.