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1.
UBV observations of the X-ray binary system A0535+26/V725 Tau at the Crimean Station of the Sternberg Astronomical Institute in 1980–1998 are presented. Based on our and published data, we analyze the photometric history of the star from 1898. Over a period of 100 years, the star apparently showed all three activity phases (B, Be, Be-shell) of Be stars. We conclude that the X-ray activity of the object is attributable to the 1970–1997 outburst of the Be star due to envelope ejection. The star's colors during the minimum light of 1998 and its 1953–1956 colors (before the outburst) correspond to the spectral type B0–B1 at the color excesses E B-V = 0.74 and E U-B = 0.48, in agreement with the current spectral type O9.7. The minimum light of 1998 and the color excesses are used to determine the colors of the additional radiation, analyze their evolution during the 1973–1997 outburst, and refine the distance to the object (3 kpc). The colors of the additional radiation at maximum light of the star (1973–1980) match the colors of a hydrogen plasma with T e = 1.5 × 104 K which is optically thick in the Balmer continuum. The brightness decline corresponds to a decrease in the optical depth of the plasma; at $V \simeq 9_.^m 1$ , it becomes optically thin in the Balmer continuum with T e = 104 K and N e = 1010 ? 1012 cm?3. This conclusion is consistent with the model of a circumstellar envelope but is inconsistent with the existence of an accretion disk around the neutron star. All the additional radiation responsible for the optical variability is produced by a single source. The intensity of the Hα emission line at maximum light (1975–1980) is triple its intensity in 1987–1997, when quasi-periodic light fluctuations with P ≈ 1400d were observed [1]. At this time, the line intensity correlated with brightness. The Hα line was in absorption at the minimum of 1998, and, at present, the star's active phase appears to have ended.  相似文献   

2.
A survey of the main characteristics of solar microwave bursts in relation to their usefulness for indicating the intensity of associated solar proton emissions suggests that time parameters give much better results than intensity or spectrum parameters. In particular, best results are obtained by using the effective, or mean, burst duration defined by $$T_M = 1/P_{max} \int_0^T {P(t)dt} $$ where T is the overall burst duration, P is the power density at time T, and P max is the maximum power density. For proton energies > 10 MeV the proton flux N p is given approximately by N p = 0.034 T M 3 particles ster?1 cm?2 s?1, where T m is in minutes, with a correlation factor of 0.8. Corresponding coefficients have been derived for a number of energy ranges. Using this parameter solar proton warnings and intensity estimates can be made with observations at only one frequency, preferably in the range 5–20 GHz.  相似文献   

3.
In space plasma, especially in the interior of plasma with weak magnetic field, Bremsstrahlung is the main mechanism of loss of the plasma energy. As shown by our calculations of the Bremsstrahlung of plasma at 1 A.U. in times of quiet sun and flare activity, the variation of intensity of plasma radiation If is directly related to the frequency of the electromagnetic wave. When the frequency f is close to that of plasma fpe, the intensity of radiation is greatly enhanced. With increasing frequency, the enhancement of the radiation intensity with frequency exhibits a slow logarithmic decrease. The brightness temperature Tb is directly proportional to the electron temperature of plasma Te and to the optical depth of medium. The overall tendencies of variations of Tb and If with frequency are identical. For the same frequency, the values of If and Tb are lower in time of quiet sun than in time of flare activity.  相似文献   

4.
The paper discusses an investigation of linear polarization produced by the transmission of light through an astronomical spectrograph slit. An experimental apparatus was designed and set up to carry out this work. The parallel beam of plane polarized light was rotated in the measuring system, by optically active of half-wave plate. The intensity of normally incident of polarized light of wavelength 0.436 μm transmitted by various slit was measured as a function of slit width. The results indicate:
  1. That the degree of polarization increased as thedepth of the narrow slit was increased.
  2. That the degree of polarization increased as thewidth of the narrow slit was decreased.
  3. That when the width of slit was widened the degree of polarization tended to approach a constant value asymptotically.
  4. That the theoretical calculation of Slater (1942) predicts the measured experimental values more accurately than Thiessen (1947) and Jones and Richards (1954).
It is shown that the existence and order of magnitude of all these effects may be predicted from the propagation losses of the electromagnetic theory of light in metallic wave guide. The paper brings out the salient points related to the degree of polarization of light by a dielectric slit of finite depth. The polarization effects from one such slit have been investigated and the results were compared with those for metallic slits.  相似文献   

5.
The modified distribution function of dust particles, f(γ), which can be determined from tail brightness profiles on the basis of mechanical theory, is discussed with special regard to its reliability and accuracy. Physical significance of f(γ) is also discussed in terms of dust model parameters, and it is shown that f(γ), if treated carefully, will serve as an effective tool in studying cometary dust. Four isophotes of Comet Arend-Roland, 1957 III, in the orange-red light (λλ 0.53–0.68 micron) obtained by Ceplecha (1958), are analysed by the numerical method described in Paper I (KIMURA and LIU 1975) with some improvements and higher approximations. The distribution f(γ) thus obtained shows a bimodal character with peaks at γ = 0.10 and 0.010 with a relative height ratio of 1 to 0.6. Dust emission rate, which is assumed to follow the inverse square law of heliocentric distance, is estimated to give PdCsca = (1.3±0.5) × 109 cm2/sec, where Pd is the rate of particle emission at 1 a.u. and the Csca is a mean effective cross section of particles for light scattering including the phase effect (the scattering angles of present interest range from about 80 to 100 degrees).  相似文献   

6.
On the basis of original observations, five white-light flares (WLF) are investigated. Evidence is given that their emission is located in two points brightening on either side of the lineH ∥ = 0 and lying at the foot points of chromospheric loops. The area of WLF is ≈ 5 × 10?6 hemisphere, i.e. ≈ 0.007 of Hα flare area; the intensity of WLF is sometimes twice that of the background at the center of the disk. WLF are resolved into more bright and fine knots of ≈ 2′ in diameter. The position of WLF coincides with the brightest knots of Hα flares which are characterized by wide wings with rapid increase and decrease. According to our estimates, the full output of the energy of a flare in the continuum and Hα are comparable; but, the energy emitted in integral light in time-unit through area-unit is by 2 orders of magnitude larger than the energy in monochromatic light.  相似文献   

7.
A new approximation of the real part of the nonrelativistic plasma dispersion function ?Z of a real argument ξ0 is proposed: namely, $$\Re Z_A (\xi _0 ) = \frac{{2\xi _0 }}{{1 - 2\xi _0^2 }}.$$ This approximation gives the exact value for ?Z when d2?Z/dξ 0 2 = 0 and gives the correct expressions for the first two terms of its expansion for large ξ0. On the basis of this approximation, a new approximate expression for whistler-mode refractive index is derived for the case of wave propagation parallel to the magnetic field in a hot anisotropic and dense plasma. Under certain conditions this expression is more convenient for practical applications in magnetospheric and/or astrophysical conditions than other approximate expressions. The approximation ?Z A was also used in deriving the approximate expression for whistler-mode instability or damping (γ), although in this case it seems to have little merit when compared with the previously used expressions for γ.  相似文献   

8.
Energy conversion rates from the extraordinary mode to the ordinary mode ofthe electromagnetic waves in the Jovian plasmasphere has been calculated for a model of the sharp boundary that is given in the vicinity of the position where ω = ωp, for an angular frequency ω and the angular plasma frequency ωp. The extraordinary mode electromagnetic wave that is obtained as a result of the transformation of a longitudinal propa- gating through an inhomogenous plasma is here considered. The results give conversion rates of 1–50 per cent, at the most, when a wave normal direction of an is nearly parallel to the boundary normal direction and when the Jovian magnetic field vector is close to the boundary normal direction within an angle range from 10° to 15°. The electric field intensity, in range from 7 to 70 mV/m, of the original electrostatic electron cyclotron plasma waves can give the power flux in a range from 10-22 to 10-20W/m2 Hz for the Jovian decameter waves observed at the Earth's surface. Efficient energy conversion is possible only when the ray direction of the emitted wave is in nearly perpendicular direction with respect to the magnetic field; this is the origin of the sharp beam emission of the Jovian decameter wave burst.  相似文献   

9.
We investigate the ‘equilibrium’ and stability of spherically-symmetric self-similar isothermal blast waves with a continuous post-shock flow velocity expanding into medium whose density varies asr ?ω ahead of the blast wave, and which are powered by a central source (a pulsar) whose power output varies with time ast ω?3. We show that:
  1. for ω<0, no physically acceptable self-similar solution exists;
  2. for ω>3, no solution exists since the mass swept up by the blast wave is infinite;
  3. ? must exceed zero in order that the blast wave expand with time, but ?<2 in order that the central source injects a finite total energy into the blast wave;
  4. for 3>ωmin(?)>ω>ωmax(?)>0, where $$\begin{gathered} \omega _{\min } (\varphi ){\text{ }} = {\text{ }}2[5{\text{ }} - {\text{ }}\varphi {\text{ }} + {\text{ }}(10{\text{ }} + {\text{ 4}}\varphi {\text{ }} - {\text{ 2}}\varphi ^2 )^{1/2} ]^2 [2{\text{ }} + {\text{ (10 }} + {\text{ 4}}\varphi {\text{ }} - {\text{ 2}}\varphi ^2 {\text{)}}^{{\text{1/2}}} ]^{ - 2} , \hfill \\ \omega _{\max } (\varphi ){\text{ }} = {\text{ }}2[5{\text{ }} - {\text{ }}\varphi {\text{ }} - {\text{ }}(10{\text{ }} + {\text{ 4}}\varphi {\text{ }} - {\text{ 2}}\varphi ^2 )^{1/2} ]^2 [2{\text{ }} - {\text{ (10 }} + {\text{ 4}}\varphi {\text{ }} - {\text{ 2}}\varphi ^2 {\text{)}}^{{\text{1/2}}} ]^{ - 2} , \hfill \\ \end{gathered} $$ two critical points exist in the flow velocity versus position plane. The physically acceptable solution must pass through the origin with zero flow speed and through the blast wave. It must also pass throughboth critical points if \(\varphi > \tfrac{5}{3}\) , while if \(\varphi< \tfrac{5}{3}\) it must by-pass both critical points. It is shown that such a solution exists but a proper connection at the lower critical point (for ?>5/3) (through whichall solutions pass with thesame slope) has not been established;
  5. for 3>ω>ωmin(?) it is shown that the two critical points of (iv) disappear. However a new pair of critical points form. The physically acceptable solution passing with zero flow velocity through the origin and also passing through the blast wave mustby-pass both of the new critical points. It is shown that the solution does indeed do so;
  6. for 3>ωmin(?)>ωmax(?)>ω it is shown that the dependence of the self-similar solution on either ω or ? is non-analytic and therefore, inferences drawn from any solutions obtained in ω>ωmax(?) (where the dependence of the solutionis analytic on ω and ?) are not valid when carried over into the domain 3>ωmin(?)>ωmax(?)>ω;
  7. all of the physically acceptable self-similar solutions obtained in 3>ω>0 are unstable to short wavelength, small amplitude but nonself-similar radial velocity perturbations near the origin, with a growth which is a power law in time;
  8. the physical self-similar solutions are globally unstable in a fully nonlinear sense to radial time-dependent flow patterns. In the limit of long times, the nonlinear growth is a power law in time for 5<ω+2?, logarithmic in time for 5>ω+2?, and the square of the logarithm in time for 5=ω+2?.
The results of (vii) and (viii) imply that the memory of the system to initial and boundary values does not decay as time progresses and so the system does not tend to a self-similar form. These results strongly suggest that the evolution of supernova remnants is not according to the self-similar form.  相似文献   

10.
A first detailed study of the low-lying electronic states of the H 3 + molecular ion in linear configuration, parallel to a magnetic field, is carried out for B=0–4.414×1013 G in the Born-Oppenheimer approximation. The variational method is employed with a single, physically adequate trial function which includes, in particular, explicitly the electronic correlation term in the form exp?(γ r 12), where γ is a variational parameter. The state of the lowest total energy (ground state) depends on the magnetic field strength. It evolves from spin-singlet 1Σ g for small magnetic fields B?5×108 G to weakly-bound spin-triplet 3Σ u for intermediate fields and eventually to spin-triplet 3Π u state for B?5×1010 G.  相似文献   

11.
The Boltzmann kinetic equation is analyzed in the MHD approximation. This analysis requires an explicit expression for the collision integral F c. In the classical theory, F c=?vf μ (1) Ωμ, where f μ (1) is the first spherical harmonic in the Galactic-cosmic-ray (GCR) distribution, Ωμ are the components of a unit particle velocity vector, and the frequency ν of collisions between GCRs and interplanetary magnetic-field nonuniformities is assumed to be a scalar. The assumption that νij is a tensor (which is the result of anisotropy in the interplanetary medium) distinguishes this study from others. Since the anisotropic GCR effects in the heliomagnetosphere are marginal, the nondiagonal elements of tensor νij were set equal to zero. Our analysis has yielded the diffusion-tensor components D ∥, and D A, which are expressed in terms of interplanetary parameters. The energy dependencies of D ∥, and D A are in good agreement with the experimental data and calculations by other authors.  相似文献   

12.
A non-relativistic calculation of the free-free opacity is made in detail for the conditions of intermediate and strong electron degeneracy. Corrections to the Born approximation are included and the ion correlations as well as the electron screening of the nuclear charge are taken into account. The free-free opacity is compared with the conductive one. It is shown that it must be taken into account when the degeneracy is not too strong, that is in the temperature-density regime where the plasma frequency ω p satisfies the condition ω p ? 2.5kT.  相似文献   

13.
The scattered radiation field in homogeneously absorbing and isotropically scattering spherical layers is studied, when the isotropic point source is at the centre. A complete frequency redistribution is assumed. It is shown, that on the inner boundaryr=R 0 of the cavity, whenR 0?1 (all radii are expressed in the path lengths), the source functionB～R 0 ?1 ln ?1/2 R 0 for the Doppler profile andB～R 0 ?3/2 for the Voigt and Lorentz profiles. The asymptotical behaviour of the source functionB(r) significantly differs from the analogous behaviour of solution for an infinite medium.  相似文献   

14.
The speed [v(R)] of coronal mass ejections (CMEs) at various distances from the Sun is modeled (as proposed by Vr?nak and Gopalswamy in J. Geophys. Res. 107, 2002, doi: 10.1029/2001/JA000120 ) by using the equation of motion a drag=γ(v?w) and its quadratic form a drag=γ(v?w)|v?w|, where v and w are the speeds of the CME and solar wind, respectively. We assume that the parameter γ can be expressed as γ=αR β , where R is the heliocentric distance, and α and β are constants. We extend the analysis of Vr?nak and Gopalswamy to obtain a more detailed insight into the dependence of the CME Sun–Earth transit time on the CME speed and the ambient solar-wind speed, for different combinations of α and β. In such a parameter-space analysis, the results obtained confirm that the CME transit time depends strongly on the state of the ambient solar wind. Specifically, we found that: i) for a particular set of values of α and β, a difference in the solar-wind speed causes larger transit-time differences at low CME speeds [v 0], than at high v 0; ii) the difference between transit times of slow and fast CMEs is larger at low solar-wind speed [w 0] than at high w 0; iii) transit times of fast CMEs are only slightly influenced by the solar-wind speed. The last item is especially important for space-weather forecasting, since it reduces the number of key parameters that determine the arrival time of fast CMEs, which tend to be more geo-effective than the slow ones. Finally, we compared the drag-based model results with the observational data for two CME samples, consisting of non-interacting and interacting CMEs (Manoharan et al. in J. Geophys. Res. 109, 2004). The comparison reveals that the model results are in better agreement with the observations for non-interacting events than for the interacting events. It was also found that for slow CMEs (v 0<500 km?s?1), there is a deviation between the observations and the model if slow-wind speeds (≈?300?–?400 km?s?1) are taken for the model input. On the other hand, the model values and the observed data agree for both the slow and the fast CMEs if higher solar-wind speeds are assumed. It is also found that the quadratic form of the drag equation reproduces the observed transit times of fast CMEs better than the linear drag model.  相似文献   

15.
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   

16.
Hydrostatic models of sunspot penumbra and umbra are evaluated using Bode's tables of monochromatic absorption coefficients andT-τ-relations given by Makita and Morimoto (1960) and by Zwaan (1965). These models are placed side by side to simulate a complete sunspot corresponding to an area of 480×10?6 of a hemisphere. Intensity profiles are evaluated for aspect angles up to 85° and compared to observations. The primary aim was to study the influence of spot transparency, which is closely related to the gas-pressure, on the Wilson-effect and on other changes in the intensity profile that appear close to the solar limb. The gas-pressures at the zero-level in the geometrical depth (z=0) corresponding to optical depth, τ=10?3, both in the umbra,P 0 u , and in the penumbra,P 0 p , appear as adjustable parameters. When curvature is taken into account, the Wilson-effect cannot be reproduced without depressing the zero-point in the geometrical scale in the umbra relative to the same layer in the photosphere. A depression of 400 km will give a reasonably good fit for the Wilson-effect providedP 0 u <P 0 P <P 0 Ph . The model we found to give the best fit is based on Makita and Morimoto'sT-τ-relations withP 0 P =3200 andP 0 u =800. We have here chosen an umbra pressure that gives a small limb-side intensity peak at the penumbra border, assuming that the bright points described by Bray and Loughhead (1964) may be interpreted in terms of a transparency effect. Other parameters measured by Wilson and Cannon (1968) are evaluated, and for some a good agreement was obtained, while for others only a qualitative effect in the same direction could be found. Surfaces along which the optical path is constant (isodiaphanous surfaces) are functions of aspect angle and well suited for visualizing the transparency in spots. It is shown how for a wide range of models the isodiaphanous surfaces get asymmetric close to the limb. This has consequences for the interpretation of the Evershed-effect. In fact, under certain conditions, a ‘masking’ effect may take place because the greater transparency in the penumbra will allow observations of a deep laying flow, which will not be visible through the more opaque photosphere. Due to the asymmetry this effect is different on the limb side and the center side. We also found the spot to show an apparent displacement away from the limb, which at a heliocentric distance of 85° amounts to about one second of arc. Intensity profiles in the near infrared at 8206 Å and at 16482 Å are evaluated, and the importance of observations in these spectral regions is emphasized.  相似文献   

17.
A statistical analysis of 87 optical selected quasars and 30 type I Seyfert galaxies is carried out in this paper. Using a quasi-Monte-Carlo method, the relation between the 2 keV monochromatic X-ray luminosity 1X and ∼2500A monochromatic ultraviolet luminosity is calculated and the result is: 1x ∝ 10bp, b = 0.93 ± 0.18 when the accretion rate ⪡ cr, and b = 0.28 ± 0.18 when > cr.A detailed semi-quantitative physical discussion of our results ruled out many available radiative mechanisms. We conclude that the most plausible dominant radiation in the band from 2500A UV to 2 keV soft X-ray is non-thermal synchrotron radiation. We discuss that when the accretion rate is growing, most of the X radiation is dragged into the black hole (the dragging effect). This is the main reason why the X-ray luminosity increases much more slowly with M than does the UV luminosity.Finally, in the context of pure luminosity evolution, we have obtained that 1x evolves more slowly than does 10p.  相似文献   

18.
Loughhead  R. E. 《Solar physics》1974,34(1):77-90
  相似文献   

19.
This paper deals with the existence of triangular points and their linear stability when the primaries are oblate spheroid and sources of radiation considering the effect of oblateness up to 10?6 of main terms in the restricted three-body problem; we see that the locations of the triangular points are affected by the oblateness of the primaries and solar radiation pressure. It is further seen that these points are stable for 0 ≤ μ ≤μ c ; and unstable for μ c  ≤ μ ≤1/2; where μ c is the critical mass value depending on terms which involve parameters that characterize the oblateness and radiation repulsive forces such that $ \mu_{c} \in (0,1/2) $ ; in addition to this an algorithm has been constructed to calculate the critical mass value.  相似文献   

20.
M. Kuperus 《Solar physics》1972,22(2):257-262
The directional dependence of the emission of sound waves in the solar atmosphere is studied. It is shown that quadrupole acoustic radiation generated in convective turbulence is strongly enhanced in the direction of the mean convective flow. The intensity in a direction with the convective velocity is proportional to (1 – M c cos)–17/2, where M c is the Mach number of the convective motion. The influence of the atmospheric cut off frequency on the transmitted acoustic spectrum is taken into account. It is suggested that low frequency atmospheric oscillations may modulate the flux of high frequency sound waves.  相似文献   

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