Bifurcation timescales in power spectra of black hole binaries and ultraluminous X-ray sources

For black hole binaries (BHBs) and active galactic nuclei (AGNs), bifurcation timescales (BTs) Δt _b exist, below which time-domain power is significantly higher than the corresponding Fourier power. Quasi-periodic oscillations (QPOs) are removed from the Fourier spectra of BHBs. A relationship between BT, black hole mass and bolometric luminosity is derived. Strong anti-correlation between BT and luminosity of Cyg X-1 is found. After removing the QPOs, BTs are also obtained for two ultraluminous X-ray sources (ULXs), M82 X-1 and NGC5408 X-1. The results support that they harbor intermediate mass black holes (IMBHs).

     

An X-ray luminosity analysis for FRIs and FRIIs

Radio galaxies are divided into two groups according to their luminosities at 178 MHz, namely Fanaroff-Riley type Is (FRIs) and Fanaroff-Riley type IIs (FRIIs) with FRIs showing lower radio luminosities than FRIIs. In this paper, the X-ray data are compiled for 183 radio galaxies (61 FRIs and 122 FRIIs), from the available literature, for the analysis of the X-ray properties. The 1 keV X-ray luminosities are calculated and discussed for the two groups, and an averaged X-ray luminosity of logL _X^{1 keV} = 41.30±2.51 erg·s⁻¹·keV⁻¹ is found for FRIs, which is lower than that for FRIIs, logL _X^{1 keV} = 43.39±3.06 erg·s⁻¹·keV⁻¹. A Kolmogorov-Smirnov (K-S) test indicates that the probability for the X-ray luminosity distributions of the two groups to be from the same parent distribution is 1.44×10⁻¹⁰. We also discuss the origin and the mechanism of the X-ray emission for FRIs and FRIIs. Supported by the National Natural Science Foundation of China (Grant Nos. 10573005 and 10633010) and the National Basic Research Program of China (Grant No. 2007CB815405)     

X-ray flares of γ-ray bursts: Quakes of solid quark stars?

A star-quake model is proposed to understand X-ray flares of both long and short γ-ray bursts (GRBs) in a solid quark star regime. Two kinds of central engines for GRBs are available if pulsar-like stars are actually (solid) quark stars, i.e., the SNE-type GRBs and the SGR-type GRBs. It is found that a quark star could be solidified about 10³ to 10⁶ s later after its birth if the critical temperature of phase transition is a few Metga-electron-volts, and then a new source of free energy (i.e., elastic and gravitational ones, rather than rotational or magnetic energy) could be possible to power GRB X-ray flares. Supported by the National Natural Science Foundation of China (Grant Nos. 10573002, 10778611, and 10873002), the National Basic Research Program of China (Grant No. 2009CB824800), the Research Foundation of Guangxi University (Grant No. M30520), and the LCWR (Grant No. LHXZ200602)     

Eccentricity modulation of a close-in planet by a companion: Application to GJ 436 system

GJ 436b is a Neptune-size planet with 23.2 Earth masses in an elliptical orbit of period 2.64 days and eccentricity 0.16. With a typical tidal dissipation factor (Q′∼10⁶) as that of a giant planet with convective envelope, its orbital circularization timescale under internal tidal dissipation is around 1 Ga, at least two times less than the stellar age (> 3 Ga). A plausible mechanism is that the eccentricity of GJ 436b is modulated by a planetary companion due to their mutual perturbation. Here we investigate this possibility from the dynamical viewpoint. A general method is given to predict the possible locations of the dynamically coupled companions, including nearby/distance non-resonant or mean motion resonance orbits with the first planet. Applying the method to GJ 436 system, we find it is very unlikely that the eccentricity of GJ 436b is maintained at the present location by a nearby/distance companion through secular perturbation or mean motion resonance. In fact, in all these simulated cases, GJ 436b will undergo eccentricity damp and orbital decay, leaving the present location within the stellar age. However, these results do not rule out the possible existence of planet companions in nearby/distance orbits, although they are not able to maintain the eccentricity of GJ 436b. Supported by the National Natural Science Foundation of China (Grant Nos. 10833001 and 10778603) and the National Basic Research Program of China (Grant No. 2007CB4800)     

Comparison of some resolution enhancement methods applied to35Cl-NQR nutation spectroscopy

The³⁵Cl nuclear quadrupole resonance spin echo nutation spectroscopy method was used to determine asymmetry parameters,η, of the electric field gradient tensor in cyanuric chloride, 1,3,5-trichloro-cyanuric acid and 1,3-dichloro-5,5-dimethylhydantoin. For comparison of advantages and drawbacks of some data processing methods we have tried integral transforms of nutation interferogram (pseudo-FID) data (Hankel and Hartley transforms) alternative to the Fourier transform. Another processing method, which provides a power spectrum estimated from time-domain data, is the maximum entropy method (MEM), and we applied the Burg algorithm version of it. We found that MEM gives the best enhancement of the nutation spectrum resolution and the signal-to-noise ratio, provided the number of autocorrelation coefficients is chosen for optimum performance of the Burg algorithm, otherwise estimated singularities in the nutation spectrum can be obscured by multiple spurious peaks or the spectrum resolution is low. In the Hankel transform with the first-order Bessel functions the improvement in resolution is achieved at the expense of the overall signal-to-noise ratio and for noisy experimental data this transform did not show reliable results. The Hartley transform gives a resolution better than the Fourier transform but worse than the two other methods. Unlike the Hankel transform after the Hartley transform the signal-to-noise ratio is not degraded. Theη parameter determined by MEM for cyanuric chloride was 18%, which is close to previously reported values. For 1,3,5-trichloro-cyanuric acidη = 20% and for the two chlorine sites in 1,3-dichloro-5,5-dimethylhydantoinη = 0 and 12% respectively. These values are in substantial agreement with the anticipated double bond character of N-Cl bonds in the two last compounds.     

X-ray spectra induced by <Superscript>129</Superscript>Xe<Superscript><Emphasis Type="Italic">q</Emphasis>+</Superscript> impacting the metal surface

Using the slow highly charged ions ¹²⁹Xe ^q+ (q = 25, 26, 27; initial kinetic T ₀⩽4.65 keV/a.u.) to impact Au surface, the Au atomic Mα characteristic X-ray spectrum is induced. The result shows that as long as the charge state of projectile is high enough, the heavy atomic characteristic X-ray can be effectively excited even though the incident beam is very weak (nA magnitude), and the X-ray yield per ion is in the order of 10⁻⁸ and increases with the kinetic energy and potential energy of projectile. By measuring the Au Mα-X-ray spectra, Au atomic N-level lifetime is estimated at about 1.33×10⁻¹⁸ s based on Heisenberg uncertainty relation. Supported by the National Natural Science Foundation of China (Grant Nos. 10574132, 10274088 and 10405025), the Talent Introduction Project of Xianyang Normal University (Grant No. 05XSYK103) and the Education Commission Foundation of Shaanxi Province (Grant No. 04JK300)     

Distribution of deep levels in Si:Au by spectral analysis of deep-level transient spectroscopy

-l eV and Δσ=1.4×10^-15 cm²) around their mean values (E₀=0.47 eV and σ₀=5.0×10^-15 cm²). No broadening for the other levels is observed in the emission rate spectrum. Accepted: 13 October 1997     

The optimal path of piston motion for Otto cycle with linear phenomenological heat transfer law

An Otto cycle engine with internal and external irreversibilities of friction and heat leakage, in which the heat transfer between the working fluid and the environment obeys linear phenomenological heat transfer law [q ∝△(T -1)], is studied in this paper. The optimal piston motion trajectory for maximizing the work output per cycle is derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston trajectories for the cases of with and w...     

Capabilities of a muon method for studying the diamagnetic domains accompanying the de Haas-van Alphen effect

This paper analyzes the capabilities of a muon (μSR) method for studying the de Haas-van Alphen effect and the diamagnetic domain structure accompanying it. It is shown that, unlike the NMR method, the μSR method makes it possible to observe the formation of a diamagnetic domain structure in all metals. It is not currently known what type of domain structure accompanies the de Haas-van Alphen effect: one-dimensional (laminar) or two-dimensional. It is shown that the line shape of the Fourier spectrum of the signal makes it possible to determine both the character of the domain structure (two-dimensional or laminar) and the magnetic field distribution in the domains. Zh. éksp. Teor. Fiz. 111, 250–261 (January 1997)     

Four-photon polarization spectroscopy of water in a millimeter-wave radiation field

Resonance (frequency 1.4 cm⁽⁻¹) changes induced in the four-photon optical spectrum of water by a millimeter-wave electromagnetic field are observed experimentally. Comparison with the spectrum of ice in the range 0‒2 cm⁽¹ shows that the action of such a field is of a structure-forming character. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 4, 266–268 (25 August 1998)     

Mass spectrometer for measuring the mass distributions of cluster ions in the range 105–107 amu

The mass analysis of heavy cluster ions in the range m/q=10⁵–10⁷ amu is investigated. A dynamic mass spectrometer is described for measurements of the mass distributions of charged particles generated in pulsed sources of polyatomic clusters in the given range. The main parameters and characteristics of the instrument are given. The distribution of cluster ions with respect to the ratio m/q is determined for a specific source of gold cluster ions formed in the inelastic sputtering of gold island films with fission fragments of ²⁵²Cf nuclei. Zh. Tekh. Fiz. 67, 107–112 (April 1997) The reported investigations have been performed under the auspices of International Science Foundation Grant No. R1S000, ISF Grant No. R1S300, ant the Government of the Russian Federation, 1994–1995.     

Carrier transport and luminescence properties of n-type GaN

The surface morphology, electrical properties and optical properties of Si doped n-type GaN were investigated. The intentional SiH₄ doped GaN films were grown by metal organic chemical vapor deposition with the electron concentration varying from 3×10¹⁶ cm⁻³ to 5.4×10¹⁸ cm⁻³. The surface morphology shows that the roughness and dislocation pits increase as the mass flow rate of SiH₄ increases, which indicates that the quality of GaN degrades gradually. The activation energy of Si in GaN with different n concentrations varies from 12 to 22 meV, which may originate from the interactions of donor wave functions. The carrier transport mechanism with increasing temperature from 100 to 420 K was concluded as the complex effect of both impurity scattering and phonon scattering. The position of the near band edge emission peak was determined by both renormalization of the band gap and B-M effect. The intensity variations of the yellow luminescence could be explained by the change of Ga vacancy concentration caused by Si doping. Supported by the National Basic Research Program of China (Grant No. 2006CB6049), the National Hi-Tech Research and Development Program of China (Grant No. 2006AA03A142), the National Natural Science Foundation of China (Grant Nos. 60721063, 60731160628 and 60676057), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20050284004) and the Natural Science Foundation of Jiangsu Province of China (Grant No. BK2005210)     

Analysis on motion of Earth’s center of mass observed with CHAMP mission

Geocenter motion (GCM) is one important topic for constructing and maintaining the terrestrial reference frame and its applications. GCM is studied from CHAMP with the multi-step approach in this paper. Geometric orbits of CHAMP in 2001–2006 are precisely determined with the kinematic method only from the satellite-borne GPS zero-difference data. Then a GCM time series is estimated from the precise kinematic orbits based on the theory of satellite dynamics to fit the CHAMP’s real geometric orbits. We compare the series with the geocenter series used in ITRF2005. Then the GCM series are analyzed with Fourier transform and wavelet transformation. The mean motions within 6 years in TX, TY and TZ directions are respectively 0.8 mm, 2.2 mm, and 7.9 mm. The trends of GCM in the three directions are 0.495 mm/a, −0.004 mm/a, and 1.309 mm/a, respectively. The long-term movement (2001–2006) indicates that the crustal figure is changing. The seasonal variations are the main component which may be excitated by the mass redistribution of Earth’s fluid layer, e.g. ocean, atmosphere and continental water. The inter-annual variations are also found in the GCM series measured with CHAMP. Supported by the International S&T Cooperation Program of China (Grant No. 2006DFA21980), the National Hi-tech R&D Program of China (Grant No. 2006AA12z303), the National Natural Science Foundation of China (Grant No. 40774009), and the Natural Science Foundation of Shandong Province, China (Grant No. Y2003E01)     

Possible origin and spectrum of ultrahigh-energy cosmic rays

The complicated form of the cosmic-ray spectrum recorded in the energy range 10¹⁷–10²⁰ eV by giant detector arrays is analyzed. It is shown that the spectrum in the region 10¹⁸–10¹⁹ eV is apparently identical to the injection spectrum with power-law exponent approximately equal to 3.2–3.3. The flat component in the region (3.2–5)×10¹⁹ eV is due to the braking of extragalactic protons by relict photons. The spectrum apparently has no blackbody cutoff at energies above 3.2×10¹⁹ eV. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 10, 729–733 (25 May 1997)     

First-principles calculations on the electronic structure and optical properties of BaSi<Subscript>2</Subscript>

The electronic structure, densities of states and optical properties of the stable orthorhombic BaSi₂ have been calculated using the first-principle density function theory and pseudopotential method. The results show that BaSi₂ is an indirect semiconductor with the band gap of 1.086 eV, the valence bands of BaSi₂ are mainly composed of Si 3p, 3s and Ba 5d, and the conduction bands are mainly composed of Ba 6s, 5d as well as Si 3p. The static dielectric function ɛ ₁(0) is 11.17, the reflectivity n ₀ is 3.35, and the biggest peak of the absorption coefficient is 2.15×10₅ cm⁻¹. Supported by the National Natural Science Foundation of China (Grant Nos. 60566001 and 60766002), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20050657003), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China (Grant No. (2005)383), the Specialized Fund of Nomarch for Excellent Talent of Science and Technology of Guizhou Province (Grant No. Z053114), the Scientific and Technological Projects for the Returned Overseas of Guizhou Province (Grant No. (2004)03), and the Top Talent’s Scientific Research Project of Organization Department of Guizhou Province (Grant No. Z053123)     

Experimental study on the local similarity scaling of the turbulence spectrum in the turbulent boundary layer

The streamwise fluctuating velocity in the turbulent boundary layer is measured under approximately medium Reynolds Number by hot wire in order to investigate the scaling properties of the overlapped turbulent spectrum among energy-containing area, inertial subrange and dissipation range based on FFT analysis. The experiment indicates that the high Reynolds flow reported before is not indispensable to produce −1 scaling. So far as the measured position is provided with much higher spatial resolution and enough closing to the wall, −1 scaling is determinate to exist when approaching medium Reynolds. The scaling ranges are supposed to begin at inner scale and end in outer scale, which reveals the local similarity of the energy spectrum over the energy-containing eddies near the wall. In the logarithmic area (y ⁺ > 130), −5/3 scaling occurs in the energy spectrum, while moving away from the wall with Reynolds numbers increasing, the inertial subrange extends to the lower wavenumbers. On the condition k ₁ η ≫ 0.1, the curves of the turbulence spectrum in the logarithmic layer are superposed, which expresses the similarity of turbulence energy distributed in Komogorov scaling area and exhibits local isotropy characteristics by virtue of the viscous dissipation. Supported by the National Natural Science Foundation of China (Grant Nos. 10832001 and 10872145), the Program for New Century Excellent Talents in Universities of Education Ministry of China, and the Plan of Tianjin Science and Technology Development (Grant No. 06TXTJJC13800)     

Chandra observations of the H2O megamaser galaxy Mrk1210

We present the first Chandra X-ray observations of the H₂O megamaser galaxy Mrk1210 (UGC4203), a Seyfert 2 galaxy at an approximate distance of D ∼ 57.6 Mpc. The Chandra X-ray image, with by far the highest angular resolution (∼1″), displays an unresolved compact core toward the nuclear region of Mrk1210. Comparisons with the previous X-ray observations in the nuclear emission and the spectral shape indicate a fairly stable phase between 2001 (BeppoSAX and XMM-Newton) and 2004 (Chandra) after a dramatic variation since 1995 (ASCA). The best-fit model of Chandra X-ray spectrum consists of two components. The soft scattered component can be best fitted by a moderately absorbed power-law model adding a spectral line at ∼0.9 keV (possibly a Ne-Kα fluorescent line), while the hard nuclear component can be well reproduced by a heavily absorbed power-law model (N _H ∼ 2×10²³ cm⁻²) with an additional line at ∼6.19 keV (close to the Fe-Kα fluorescent line). The derived absorption-corrected X-ray luminosity implies that the dramatic variation of spectral properties is caused by significant changes of the absorbing column density along the line-of-sight, while the intrinsic nuclear X-ray luminosity remains stable. In this case, the absorbers should be anisotropic and its size can be constrained to be less than 0.0013 pc. In addition, we also estimate the mass of central engine, the disk radius and the accretion rate of the accretion disk to be 10^7.12±0.31 M _⊙, ∼1 pc and 0.006, respectively. Supported by the National Natural Science Foundation of China (Grant No. 10633010) and the Natural Science Foundation of Guangdong Province, China (Grant No. 8451009101001047) Recommended by Zhou YouYuan     

Influence of amplified spontaneous emission and fluorescence of β-carotene on stimulated Raman scattering of carbon disulfide

β-carotene with double fluorescence characteristics and large third-order optical nonlinearities, which is dissolved in the carbon disulfide (CS₂) as the core medium of a liquid core optical fiber (LCOF), is applied in the study of the CS₂ stimulated Raman scattering (SRS). The results of this study show that when the concentrations of solution are more than 3.72×10⁻⁷ mol/L, the amplified spontaneous emission (ASE) of β-carotene is the main factor influencing the threshold and intensity of Stokes lines; when the concentrations of solution are lower than 3.72×10⁻⁷ mol/L, the ASE disappears and the fluorescence plays the key role: The high-order Stokes lines may be observed at very low input-laser power, and the Stokes thresholds decrease as the solution concentration increases. The result may be widely used in the study of broadband stimulated radiation laser and seeding laser. Supported by the National Natural Science Foundation of China (Grant No. 10774057)     

Research on ultracold cesium molecule long-range states by high-resolution photoassociative spectroscopy

In this paper, an ultra-high resolution photoassociation spectroscopy study on photoassociation of cesium atoms is reported. The cold cesium gas in the magneto-optical trap is illuminated by a photoassociation laser with red-tuning as large as 40 cm⁻¹ below the 6S _1/2 + 6P _3/2 dissociation limit, and the photoassociation to the excited state ultracold molecule is detected. High signal-to-noise ratio is obtained by using the lock-in detection of the fluorescence from the modulated cold Cs atoms. The 0 _g ⁻ , 1_g and 0 _u ⁺ long-range states which correspond to 6S _1/2 + 6P _3/2 dissociation limit are present in the photoassociation spectrum. The effective coefficients of leading long-range interactions and the corresponding vibrational quantum number are obtained using LeRoy-Bernstein Law. It is found that photoassociation process creates rotating molecules and the high J value is a hint that higher partial waves participate in the PA process in the presence of trapping laser. Supported by 973 Program of China (Grant. No. 2006CB921603), the National Natural Science Foundation of China (Grant Nos. 10574084, 60678003, and 60778008), the Special Foundation for State Major Basic Research Program of China (Grant No. 2005CCA06300), and the Youth Science Foundation of Shanxi Province of China (Grant No. 20041013)