Chinese Astronomy最新文献

This article puts forward a new method for the theoretical analysis of the X-radiation spectrum of impulsive hard X-ray bursts. It points out that the electron density energy state function must obey the fundamental kinetic equation. In the case of several model source functions, the electron density energy spectra are deduced. This can serve as a basis for an analysis of the spectrum of X-radiaiton in impulsive hard X-ray bursts. The article also makes a preliminary discussion of these energy state functions which help to explain the phenomena of softening of the X-radiation spectrum.

83 pulsars are statistically studied in this paper. The main results are as follows:

• 1.

  (1) Taking the ratio λ of the loss rate of rotational energy to the radio luminosity of pulsars as a parameter of classification, we divide the 83 pulsars into 3 categories. The plots of $\text{P}\text{dot}\text{-P, L}{}_{\mathrm{<mtext>radio</mtext>}}\text{-P}\text{and}\text{L}{}_{\mathrm{<mtext>radio</mtext>}}\text{-t}$ show that different categories of pulsars have different evolutionary tracks and physical properties. The evolutionary tracks of our 3 categories are similar to those of the model proposed by Lyne et al. (1975) [1] which involves a secular decay of magnetic dipole moment, suggesting that the different categories have different time constants of decay, or different initial values of magnetic moment at birth.

• 2.

  (2) The radio luminosities of pulsars of various categories are all closely correlated with the magnetic energies and “twining” magnetic energies at the light cylinder, and not correlated with the magnetic energies at the surface of the neutron star. This shows that localized radiation regions are in the vicinity of the light cylinder. These magnetic energies may be the energy sources of pulsar radiation.

• 3.

  (3) The rightmost pulsars in the $\text{P}\text{dot}\text{-P}$ plot form a cut-off line of radio radiation, with a slope of −4, so that it is a line of constant “twining” magnetic energy. This line is closer to the observational results than the cut-off line, proposed by Lyne et al. (1975) [1], with a gradient of −5. This results gives support to the idea that energy is accumulated and released in the vicinity of the light cylinder.

This paper describes the designing of a four-lens corrector system for parabolic mirrors incorporating a final optimization with a computer. An example for the Palomar 5.08 m telescope is worked out, which proves to give smaller image blur circles than Wynne's design [4].

In this paper a statistical investigation has been made on some characteristics of the evolution of radio galaxies with double structure. 77 radio galaxies with known redshifts are selected. The main results are as follows: 1. In the angular size-redshift diagram, there appears to be a lower bound (θ_min −z), which corresponds to a minimum linear size $\text{D}{}_{\mathrm{<mtext>min</mtext>}}\text{⋍ 40}\text{kpc}$. It looks as though all double structures are initially formed with this size. 2. The radio luminosity (L), volume (V) and total energy (E) of individual components vary with the linear separation D. There may be a critical separation $\text{D}{}_{\mathrm{c}}\text{⋍ 600}\text{kpc}$ such that when D < D_c, L, V and E increase steadily with the increasing D; while for D > D _c, L, V and E remain essentially constant. Somewhat unexpectedly, there seems to be no correlation between E/V (or L/V) and D. 3. Among radio galaxies with the largest linear size, the absolute visual magnitudes appear to get fainter with increasing D at the rate of about +4.8^m/Mpc.

It is pointed out that (1) the equations used by Yumi and Wako [1] and by Okuda [2,3] to calculate the non-polar variations in the latitude of stations, are equivalent, and either set by itself gives only indeterminate solutions. (2) The solutions given by these authors depend on the assumptions made and the assumptions lack sufficient bases. Their results are therefore unreliable. (3) Although the authors managed to make (o-c) and $\text{Δ}\text{z}$ to approach zero their calculations, this does not prove that their results are correct.

We have investigated the propagation of perturbations in a gravity-stratified atmosphere without making the adiabatic assumption and we have obtained rather different results from those under the adiabatic assumption, in particular, the height at which the perturbation becomes a shock wave was found to be much lower. Our results lead to the view that the heating of the corona and chromosphere may be caused by perturbations starting at various heights above the photosphere, rather than wholly by accoustic and MHD waves originating in the convective zone below the photosphere.

In the Winters of 1975 and 1977, observations of flare stars in the Taurus Cloud region were made with the 40 cm double astrograph of the Purple Mountain Observatory. Two flare stars and one repeat outburst of FH Tau were identified. We give also a comparison between the flare stars of this region and the ϱ Oph region.

The variation with r of C_z², the dispersion of velocities in z is obtained by direct integration. We also obtain the variation of the radial dispersion of velocities with r through the stability of the density wave in a three-dimensional dishlike galaxy. In the solar neighborhood, the theoretical values of C_r and C_z are in fair agreement with the observed values. And towards the centre of the galaxies, the value of C_r/C_z approaches 1.

Okuda's method of determining the local non-polar terms is shown to be incapable of achieving its intended aim.

The present paper identifies and rejects outliers in an observational series on the basis of two statistics, the sum of residual squares from polymomial fitting and predicted residual in recursive filtering. An example is given. The present method is effective against both single and grouped outliers.