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1.
In order to study the statistical characters and physical significance of the color indexes and orbital parameters of Centaurs, we have analyzed the color and orbit parameter correlations by using statistical methods according to the known color indexes of 39 Centaurs and their respective orbital parameters. We find that all the correlations of B − V vs. V − R, V − R vs. R − I, B − V vs. R − I and B − R vs. R − I are strong. The Centaurs exhibit obvious redblue double-color property, and the point of demarcation is close to B − R = 1.4. The distributions of the various color indexes of Centaurs exhibit the normal distribution. For the correlations between colors and orbital parameters, except for the weak correlations between B − V and the orbital inclination i as well as between V − R and the orbital semi-major axis a, no evident correlation has been found between color indexes and orbital parameters.  相似文献   

2.
Using the broad band spectral index of 164 blazars in a low state, we studied the possible correlation between different broad band spectral index (α r.ir , α r.o , α r.x , α r.γ , α ir.o , α ir.x , α ir.γ , α o.x , α o.γ , α x.γ ). We also studied the possible correlation between different broad band spectral index of high-frequency peaked Bl Lac object (HBL), low-frequency peaked BL Lac object (LBL) and flat spectral radio quasars (FSRQs), respectively. The strong anti-correlations were found between α r.o and α o.γ , between α r.o and α x.γ in a low state for our blazar sample. For LBL and FSRQs, the strong anti-correlations were found between α r.ir and α ir.x , between α r.o and α o.x , and between α r.o and α o.γ in a low state. Based on these results, we suggested that the seed photons of the γ-ray drive from both the jet and the external accretion disk or the broad-line region, and that the subclasses of blazars seem to the different emission mechanism.  相似文献   

3.
We studied the relationship between the power-law exponent γ on the rigidity R of the spectrum of galactic cosmic-ray (GCR) intensity variation (δD(R)/D(R)∝R ?γ ) and the exponents ν y and ν z of the power spectral density (PSD) of the B y and B z components of the interplanetary magnetic field (IMF) turbulence (PSD～f ?ν , where f is the frequency). We used the data from neutron monitors and IMF for the period of 1968?–?2002. The exponents ν y and ν z were calculated in the frequency interval Δf=f 2?f 1=3×10?6 Hz of the resonant frequencies (f 1=1×10?6 Hz, f 2=4×10?6 Hz) that are responsible for the scattering of GCR particles with the rigidity range detected by neutron monitors. We found clear inverse correlations between γ and ν y or ν z when the time variations of the resonant frequencies were derived from in situ measurements of the solar wind velocity U sw and IMF strength B during 1968?–?2002. We argue that these inverse relations are a fundamental feature in the GCR modulation that is not restricted to the analyzed years of 1968?–?2002.  相似文献   

4.
The (Newton + Yukawa)-type gravitational potential V(r)=?(γ M/r)[1+Aexp?(?r/B)](γ= the gravitational constant as measured at infinity, M= the mass of the source, A, B are constants) is considered in the framework of the Sciama linear approach to Mach’s principle. The coupling constant A of the Yukawa component is found to be related to the mass density and size of the observable (causally connected) universe.  相似文献   

5.
Nearly 2500 shock crossings from HEOS-1, HEOS-2 and 5 IMP spacecraft, covering most of the northern and part of the southern bow shock surface for X values X > ? 20 RE, have been used to carry out a detailed study of the three-dimensional shape and location of the bow shock. The influence of the different solar wind conditions has been reduced by normalising the observed crossings to an average solar wind dynamical pressure (N0 = 9.4 cm?3, V0 = 450 kms?1). It has been shown that the shock surface is symmetric with respect to the ecliptic plane and intersects the coordinate axes at 11.9 RE (X), + 27.0 and ? 22.9 RE (Y), + 23.9 and ? 24.5 RE (Z) for the average dynamical pressure (N0 = 9.4 cm?3, V0 = 450kms?1, with MA = 9.3, MMS = 6.1). The observed aberration of the shock surface is 8.9° ± 1°, i.e. 5.1° larger than the aberration predicted from the Earth's motion. This asymmetry around the solar wind apparent direction is described by equation (6) for different Mach numbers MA and confirms the predictions of Walters [J. geophys. Res. 71, 1319 (1964)] and Michel [J. geophys. Res. 70, 1 (1965)].The magnetosheath thickness is 3.3 RE along the X-axis, 11.4 RE (+ Y), 8.7 RE (? Y), 9.9 RE (+Z) and 10.9 RE along the negative Z axis.  相似文献   

6.
The paper describes a comparison of vertical electron drift in the F-region (Vz) measured by VHP incoherent scatter radar at Jicamarca with the corresponding variations of geomagnetic horizontal field (H) and the maximum frequency reflected from The Es layer (Es) at Huancayo during the geomagnetic storm period 7–9 March, 1970. The Vz is generally upward during the daytime at the equator, but during 7–9, March, 1970, Vz was negative for brief periods associated with negative bays in H. These periods of abnormally low or of downward Vz correspond closely with the period of complete disappearance of the q type of Es layer. The magnetic bays associated with the intensification of ring current do not affect the equatorial Es- q and it is only the negative bays in H at the equator due to the ionospheric current flowing westward, that cause sudden disappearance of Es? q. It is suggested that the q type of Es is due to cross-field instability created in the electrojet region due to interaction of northward magnetic field and vertical upward Hall polarization electric field when the plasma density gradient is upward. The sudden disappearances of Es? q are due to the reversal of the horizontal electric field in the equatorial ionosphere and thereby due to the reversal of the equatorial electrojet currents. These reversals of electric field may be due to the imposition on the normal Sq field of another westward electric field.  相似文献   

7.
We find that Einstein’s like field equations with coordinate-dependent cosmological “constant” Λ(x i ) imply a non geodesic law of motion for test particles moving in a continuous distribution of incoherent matter (“dust”). The deviation from the geodesic law depends on the derivatives ?Λ/? x i and, in the weak field approximation, causes an anomalous acceleration A～(Vc 2/γ ρ)?Λ/? t+(c 4/γ ρ)?Λ/? r where V=dr/dt, c=the speed of light, γ=8π G with G=the gravitational coupling, ρ=the mass density of the cloud, r and t are the radial and time coordinate respectively. Reasonable assumptions on Λ=Λ(t) give A<10?8 cm/s2 when ρ>10?29 g/cm3 i.e. in all known astrophysical systems. A possible connection with the anomalous Pioneer acceleration is shortly discussed in the case of a cosmological “constant” coupled to matter.  相似文献   

8.
In this paper, we search the existence of Bianchi type I cosmological model in f(R,T) gravity, where the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R and of the trace of the stress-energy tensor T. We obtain the gravitational field equations in the metric formalism, and reconstruct the corresponding f(R,T) functions. Attention is attached to the special case, f(R,T)=f 1(R)+f 2(T) and two examples are assumed for this model. In the first example, we consider the unification of matter dominated and accelerated phases with f(R) gravity in anisotropic universe, and in the second instance, model of f(R,T) gravity with transition of matter dominated phase to the acceleration phase is obtained. In both cases, f(R,T) is proportional to a power of R with exponents depending on the input parameters.  相似文献   

9.
The fast spinning B-star Regulus has recently been found to be orbited by a fainter companion in a close circular path with orbital period P b=40.11(2) d. Being its equatorial radius R e 32% larger than the polar one R p, Regulus possesses a remarkable quadrupole mass moment Q. We investigate the effects of Q on the orbital period P b of its companion in order to see if they are measurable, given the present-day level of accuracy in measuring P b. Conversely, we will look for deviations from the third Kepler law, attributed to the quadrupole mass moment Q of Regulus, to constrain the ratio γ=m/M of the system’s masses. The impact of Q on the orbital period is analytically worked out with a straightforward perturbative approach. The resulting correction P Q is compared to other competing dynamical effects. P Q and the Keplerian period P Kep are expressed in terms of the phenomenologically determined system’s parameters; γ is treated as an unknown. P Q is compared to the observational accuracy in measuring the orbital period δ P b=0.02 d and to the systematic uncertainty δ(P Kep) due to the errors in the system’s parameters entering it. The discrepancy ΔP=|P b?P Kep| is examined in order to see for which values of γ it becomes statistically significant. The physical meaning of the obtained range of values for γ is discussed in terms of Q. P Q is larger than δ P b but still smaller than the systematic uncertainty in P Kep by two orders of magnitude. The major sources of bias are the velocity semiamplitude K of the motion of the primary and its mass M. Assuming edge-on configuration, i.e. i=90 deg, if γ?0.096 Q would be positive, i.e. Regulus would be prolate, contrary to the observations. If γ?0.078 Q would be negative, but its magnitude would be one-two orders of magnitude larger than the approximate estimate Q≈M(R p 2 ?R e 2 )=?2.4±0.5×1049 kg?m2. Regulus is the first extrasolar binary system in which the orbital effects of the asphericity of the primary are larger than the observational sensitivity; moreover, no other competing aliasing orbital effects are present. Thus, it is desirable that it will become the object of future intensive observational campaigns in order to reduce the systematic uncertainty due to the system’s parameters below the measurability threshold.  相似文献   

10.
The paper deals with a spatially homogeneous and anisotropic universe filled with perfect fluid and dark energy components. We consider the f(R,T) theory according to holographic and new agegraphic dark energy in the Bianchi type I universe. In this study, we concentrate on two particular models of f(R,T) gravity namely, R+2f(T) and f(R)+λT. We conclude that the derived f(R,T) models can represent phantom or quintessence regimes of the universe.  相似文献   

11.
We have investigated the characteristics of the distribution of neutron exposures (“DNE” hereafter) in the He-shell nucleosynthesis regions in the model of s-process nucleosynthesis in low-mass AGB (Asymptotic Giant Branch) stars in 13C radiatively burning conditions. The result indicates that although the DNE obtained with this model is still approximately exponential, like those of the previous convective s-process scenarios, the relation between the neutron exposure Δτ of each pulse and the mean neutron exposure τ0 is no longer τ0 = −Δτ/ln r, rather, it is now approximately τ0 = −Δτ/ ln{q[1.0020 + 0.6602(r − q) + 4.6125(r − q)2− 10.8962(r − q)3+ 13.9138(r − q)4]} (r is the overlap factor, q is the mass ratio of the 13C shell to the He shell). This formula unifies the stellar model of radiative s-process with the classical model from the angle of DNE.  相似文献   

12.
The effect of electron inertia on kinetic Alfven wave has been studied. The expressions for the dispersion relation, growth/damping rate and growth/damping length of the inertial kinetic Alfven wave (IKAW) are derived using the kinetic approach in cusp region. The Vlasov-kinetic theory has been adopted to evaluate the dispersion relation, growth/damping rate and growth/damping length with respect to the perpendicular wave number k⊥ρi (ρi is the ion gyroradius) at different plasma densities. The growth/damping rate and growth/damping length are evaluated for different me/βmi, where β is the ratio of electron pressure to the magnetic field pressure, mi, e are the mass of ion and electron, respectively, as I=me/βmi represent boundary between the kinetic and inertial regimes. It is observed that frequency of inertial kinetic Alfven wave (IKAW) ω is decreasing with k⊥ρi and plasma density. The polar cusp is an ideal laboratory for studies of nonlinear plasma processes important for understanding the basic plasma physics, as well as the magnetospheric and astrophysical applications of these processes.  相似文献   

13.
We have constructed Locally Rotationally Symmetric Bianchi type I (LRSBI) cosmological models in the f(R,T) theory of gravity when the source of gravitation is the bulk viscous fluid. The models are constructed for f(R,T)=R+2f(T) and f(R,T)=f 1(R)+f 2(T). We found that in the first case the model degenerates into effective stiff fluid model of the universe. In the second case we obtained degenerate effective stiff fluid model as well as general bulk viscous models of the universe. Some physical and kinematical properties of the models are also discussed.  相似文献   

14.
The conditions under which a head-on collision between a disk galaxy and a spherical galaxy can lead to ring formation are investigated, using the impulsive approximation. The spherical galaxy is modeled as a polytrope of indexn=4 and radiusR S and the disk galaxy as an exponential disk whose surface density is given by \(\sigma (r) = \sigma _c e^{ - 4r/R_D } \) , where σ c is the central density andR D is the radius of the disk. The formation and properties of the rings are closely related to the fractional change in binding energy of the disk galaxy, given by ΔU/?U?=γ D β D , where (GM S 2 R D )/(V 2 M D R S 2 ),M S andM D being the masses of the spherical and disk galaxies, respectively, and β D ≡β D (n, σ, ?,i) is a function of the models of the two galaxies, the ratio of the radii of the two galaxies ?=R S /R D , and the angle of inclinationi, of the disk to the direction of relative motion of the two galaxies. Calculations are made for the caseR S =R D . Since practically the entire mass of the spherical galaxy, for the chosen model, lies within 1/3 of its radius, the radius of the spherical galaxy is effectively \(\tfrac{1}{3}\) that of the disk galaxy. It is found that as a result of the collision, the innermost and the outer parts of the disk galaxy are not much affected, but the intermediate region expands and gets evacuated, leading to the crowding of stars in a preferential region forming a ring structure. The rings are best formed for a normal, on-axis collision. For this case, rings form when ΔU/|U| lies between \(\tfrac{1}{2}\) and 2, while they are very sharp and bright when ΔU/|U| lies between \(\tfrac{1}{2}\) and 1. Within this range, as ΔU/|U| increases, the rings become sharper and their positions shift outwards with respect to the centre of the disk galaxy. The relationship $$\gamma _D = 0.0016 + 0.045s_{{\text{max}}}^2 ,$$ wheres max is the radial distance of the density maximum of the ring from the centre of the disk galaxy (measured in terms of the radius of the disk galaxy as unit) enables us to finds max from γ D and vice versa, and interpret some prominent ring galaxies. The effect of introducing a bulge to the disk is to distribute the tidal disruptive effects more evenly and, hence, reduce the sharpness of the ring.  相似文献   

15.
Much work has been done taking into account the possibility that the gravitational constant G may vary with cosmological time t (or with the cosmological scale factor a(t)). The same may be said about the speed of light c. We present here two important remarks on these subject. These remarks include G(t) and c(t) varying with time with the restriction 8πG/c 4=constant.  相似文献   

16.
We investigated the NLTE formation of the solar spectrum of neutral silicon using 3D hydrodynamic model of the solar atmosphere and realistic atomic model. We show that, within the intergranular region, combined action of the deficit in the source function and excess in opacity due to the overpopulation of the lower Si I levels leads to a considerably higher increase in the central depth D and equivalent width W of these lines as compared to the granules. We have fitted silicon abundances A W and A D from the equivalent widths W and central depths D for 65 Si I lines using a 3D model. We show that a total error in the calculated silicon abundance due to neglecting NLTE and 3D effects, as well as the uncertainty in the van der Waals broadening constant γ6, turns out to be ?0.1 dex. Using a semiclassical theory by Anstee, Barklem, and O’Mara in calculating γ6 yields a fair coincidence between the values of A W and A D , because the average difference A W — A D does not exceed 0.01 dex for both NLTE and LTE. When applying the Unsold’s approximation in calculating γ6 with an enhancement factor E = 1.5, the abundances A W and A D proved to be in disagreement with one another. We analyzed the “solar” oscillator strength scale by Gurtovenko and Kostik, as well as the experimental one by Garz and Becker et al. We show that using “solar” oscillator strengths log gfw leads to a minimum trend with the equivalent widths for NLTE abundances A W , A D , their difference A W — A D , and standard deviations. The NLTE abundance of silicon obtained using solar oscillator strength scale by Gurtovenko and Kostik is A W NTLE = 7.549 ± 0.016. This value is in good agreement with the value of silicon abundance recommended by Grevesse and Sauval for the CI chondrite meteorites.  相似文献   

17.
The K-correction is made up of an emission line component and a continuum component. These two components are iteratively determined in this paper from line widths and intensities, redshifts, U,B,V colours and radio spectral indices for 355 quasars. The colors B-V and U-B, corrected for the emission line portion of the K-correction, are plotted against Z, giving 2 mean relations. Eliminating Z between these gives a mean optical continuum, which is then used to calculate the continuum portion of the K-correction.  相似文献   

18.
The chromophores responsible for coloring the jovian atmosphere are embedded within Jupiter’s vertical aerosol structure. Sunlight propagates through this vertical distribution of aerosol particles, whose colors are defined by ?0(λ), and we remotely observe the culmination of the radiative transfer as I/F(λ). In this study, we employed a radiative transfer code to retrieve ?0(λ) for particles in Jupiter’s tropospheric haze at seven wavelengths in the near-UV and visible regimes. The data consisted of images of the 2008 passage of Oval BA to the south of the Great Red Spot obtained by the Wide Field Planetary Camera 2 on-board the Hubble Space Telescope. We present derived particle colors for locations that were selected from 14 weather regions, which spanned a large range of observed colors. All ?0(λ) curves were absorbing in the blue, and ?0(λ) increased monotonically to approximately unity as wavelength increased. We found accurate fits to all ?0(λ) curves using an empirically derived functional form: ?0(λ) = 1 − A exp(−Bλ). The best-fit parameters for the mean ?0(λ) curve were A = 25.4 and B = 0.0149 for λ in units of nm. We performed a principal component analysis (PCA) on our ?0(λ) results and found that one or two independent chromophores were sufficient to produce the variations in ?0(λ). A PCA of I/F(λ) for the same jovian locations resulted in principal components (PCs) with roughly the same variances as the ?0(λ) PCA, but they did not result in a one-to-one mapping of PC amplitudes between the ?0(λ) PCA and I/F(λ) PCA. We suggest that statistical analyses performed on I/F(λ) image cubes have limited applicability to the characterization of chromophores in the jovian atmosphere due to the sensitivity of I/F(λ) to horizontal variations in the vertical aerosol distribution.  相似文献   

19.
In this work, we analyze the X-ray spectral indices of the 245 Fermi-detected blazars. Relations between the γ-ray emission and the X-ray emission are our research focuses. Our analysis shows that: (1) the X-ray spectral indices of the Fermi/LAT-detected-blazars (α X|Fermi ), have similar distributions with those of non-Fermi-detected blazars (α X|non-Fermi ), and the averaged value \(\overline{\alpha_{X|Fermi}}\simeq\overline{\alpha_{X|non\mbox{-}Fermi}}\) ; (2) X-ray spectral indices are strong anti-correlated with the logarithmic Doppler factors, log(δ)=?(0.27±0.10)α X +(1.09±0.14), with the correlative coefficient R=?0.33, the chance probability P=1.9 %; (3) X-ray spectral indices (α X ) and γ-ray spectral indices (α γ ) show strong anti-correlation, α X =?(0.62±0.11)α γ +(1.91±0.12), R=?0.35, P<0.001 %.  相似文献   

20.
Assuming that the formation of the ring current belt is a direct consequence of an enhanced crosstail electric field and hence of an enhanced convection, we calculate the total ring current kinetic energy (KR) and the ring current energy injection rate (UR) as a function of the cross-tail electric field (ECT); the cross-tail electric field is assumed to have a step function-like increase. The loss of ring current particles due to recombination and charge-exchange is assumed to be distributed over the whole ring current region. It is found that: (1) the steady-state ring current energy KR is approximately linearly proportional to ECT; (2) the characteristic time tc for KR to reach the saturation level is 3–4 h; (3) the injection rate UR is proportional to ECTβ where β ? 1.33?1.52; and (4) the characteristic time tp for UR to reach the peak value is 1–2 h and the peak UR value is 50% higher than the steady-state value. Since β is now determined specifically for an enhanced convection, an observational determination of the relationship between ECT(or φCT) and UR is essential to a better understanding of ring current formation processes. If the observed β is greater than 1.5, additional processes (e.g. an injection of heavy ions from the ionosphere to the plasma sheet and subsequently to the ring current region) may be required.  相似文献   

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