Chinese Astronomy最新文献

Comet Tsuchinshan (1977q) was discovered at Purple Mountain Observatory on Nov. 3, 1977. The osculating orbital elements (referred to the barycenter of the sun and Mercury) given in table 1 are derived from 42 observations Nov. 3, 1977 to Jan. 10, 1978 at our observatory and abroad, taking into account the perturbations of all major planets. In all the observations the rms residual is 1.″78. Our observations are also published in table 2. With the elements thus obtained, the appropriate ephemerides in recent years have been calculated and listed in table 4. And then, in consideration of accurate perturbations, we compute the original and future orbits (referred to the center of mass of solar system) while the comet is about 60 A. U. from the sun. The results that both the original and future orbits are hyperbolicaare given in table 5 and may be compared with the osculating elements. Nevertheless, the two months observed interval for determining orbit is short. In order to obtain the more reliable conclusion, it is necessary to make some efforts for increasing the observed arc.

The relative proper motions of 64 RR Lyrae variables are determined using Turner's method. The first-epoch positions are taken from the Carte du Ciel Astrographic Catalogue, while the second-epoch positions are measured positions from plates taken with the 40-cm refractor (f=6.9 m) of the Zô-Sè Section, Shanghai Observatory, in 1962–1965. The average interval between the two epochs is about 60 years. The mean error in the proper motion is ± 0.005″/y.

The absolute proper motions of these variables are found after correcting for the parallactic motions and the galactic differential rotation. The results are given in 3 TABLES.

The propagation and evolution of linear waves in a self-gravitating medium are discussed in a comparatively general way. In one special case, the well-known Jeans formula is recovered; in another, an important property of unstable waves in a self-gravitating medium is obtained, namely, the equiphase surfaces of the wave are “frozen” in the moving medium. When the motion of the basic state is one of shear flow (or differential rotation), this property implies that unstable waves would evolve into a quasi-stationary state. This shows that, for a self-gravitating medium, besides the usual non-linear effects, there is a special mechanism within the linear theory which prevents the infinite growth of unstable waves. Possible relation of this effect to the origin of celestial bodies is pointed out.

In this paper a numerical solution of the equations of transfer of the Stokes parameters in the presence of magnetic fields has been carried out. This yields the profiles of the Stokes parameters for three magneto-sensitive spectral lines (FEI λλ 6302.499, 6173.341, 5250.216). The magnetic broadening, temperature sensitivity and some other properties of these lines have also been investigated.

In Unno's pioneering work, an algebraic solution of the equations of transfer of the Stokes parameters were obtained under a series of assumptions. Two of these are: 1) The source function B, varies linearly with the optical depth τ_λ; 2) The atmosphere follows the Milne-Eddington model. In this paper we have abandoned both these unrealistic assumptions. In consequence, our numerical solution agrees with observations better than the algebraic solution of Unno.

In a reflector, the light loss is at a minimum at the prime focus, but it is too awkward to mount a spectrometer of any size there. In this paper, I propose to place the slit at the prime focus to be followed immediately by a collimating mirror as shown in Fig. 1. The collimated beam diameter can be as large as one-ninth of the telescope aperture, and a maximum spectral resolving power of 10⁵ can be achieved. This new design can replace with advantage the conventional Cassegrain spectrometer in all types of work. It is eminently suited for use in the next generation of telescopes such as the MMT and the single telescope array.

By taking the variation of the magnetic energy of a given system $\text{1}\text{8π}\text{∫}{}_{\mathrm{\upsilon }}\text{(∇ ×}\text{A}\text{)}{}^2\text{dτ}$ with the constraint that $\text{∫}{}_{\mathrm{\upsilon }}\text{A}\text{· ∇ ×}\text{A}\text{dτ =}\text{const.}$ and under the condition that the potential part ∇φ of E is defined as $\text{∇φ =}\text{c}\text{4πσ}\text{∇ ∫ α}\text{B}\text{.d1}$ which ensures that $\text{∂}\text{A}\text{∂t}\text{.}\text{B}\text{= 0}$, it will be shown that the force-free factor α is a constant for a stable magnetic field.

In this paper we discuss the range of variation of the orbital inclination and the latitude with respect to the invariable plane and give the necessary and sufficient conditions for the motion to be within the permissible range. We further prove that the range of variation of the inclination attains its maximum (minimum) at the collinear configuration with the maximum (minimum) value of the potential function.