Volume 11, Issue 1
March 1990, pages 1-123
pp 1-10 March 1990
The in-plane motion of a Geosynchronous satellite under the gravitational effects of the sun, the moon and the oblate earth has been studied. The radial deviation (Δr) and the tangential deviation (r_{c}Δθ) have been determined. Herer_{c} represents the synchronous altitude. It has been seen that the sum of the oscillatory terms in Δr for different inclinations is a small finite quantity whereas the sum of the oscillatory terms inr_{c}Δθ for different inclinations is quite large due to the presence of the low-frequency terms in the denominator
pp 11-22 March 1990
On the effect of the eccentricity of a planetary orbit on the stability of satellite orbits
The effect of the eccentricity of a planet’s orbit on the stability of the orbits of its satellites is studied. The model used is the elliptic Hill case of the planar restricted three-body problem. The linear stability of all the known families of periodic orbits of the problem is computed. No stable orbits are found, the majority of them possessing one or two pairs of real eigenvalues of the monodromy matrix, while a part of a family with complex instability is found. Two families of periodic orbits, bifurcating from the Lagrangian points L_{1}, L_{2} of the corresponding circular case are found analytically. These orbits are very unstable and the determination of their stability coefficients is not accurate, so we compute the largest Liapunov exponent in their vicinity. In all cases these exponents are positive, indicating the existence of chaotic motions
pp 23-28 March 1990
The magnetohydrodynamics of stellar structures
G. S. Dubey U. S. Pandey J. P. Singh L. K. Singh S. N. Singh
The equation governing the equilibrium of a centrally-symmetric, self-gravitating distribution of matter is obtained by assuming that matter is described by magnetofluid and it is shown that the equation of stellar structure described by an ideal fluid is recovered when magnetic fieldh is vanishing
pp 29-35 March 1990
The Newtonian forces in the Kerr geometry
Sandip K. Chakrabarti A. R. Prasanna
We study the properties of the ’Newtonian forces’ acting on a test particle in the field of the Kerr black hole geometry. We show that the centrifugal force and the Coriolis force reverse signs at several different locations. We point out the possible relevance of such reversals particularly in the study of the stability properties of the compact rotating stars and the accretion discs in hydrostatic equilibria
pp 37-42 March 1990
Emission spectrum of hot R OB star MV Sgr
N. Kameswara Rao L. Houziaux Sunetra Giridhar
The new spectroscopic observation of MV Sgr obtained at ESO in 1987 July shows enhanced emission lines of He I λ3889, [SII] λ4068 relative to the observations discussed by Jeffreyet al. (1988). The presence of [SII] λ4068 indicates the presence of planetary-nebulae-like envelope around the star. Although the radial velocity of the absorption lines and Fe II emission lines do agree with the velocity given by Jeffreyet al., the [SII] λ4068 and probably He I emission lines appear to behave differently.
pp 43-48 March 1990
The chromospherically active solar-type spectroscopic binary HD 191262
HD 191262 is a double-lined spectroscopic binary consisting of two slightly unequal solar-type stars in an orbit’ with a period of 5.43435 days. The system is both synchronized and circularized and is probably at least as old as the Sun. The inclination of the system is about 45°
pp 49-66 March 1990
Relativistic magnetofluid disc with nonzero radial velocity in Schwarzschild geometry
In this paper we consider the equilibrium of a magnetofluid disc in Schwarzschild background with an external magnetic field, having the azimuthal and the radial components of the flow velocity nonzero. The electrical conductivityσ of the fluid is taken to be finite and thus the solution for the electromagnetic field is required to satisfy the Ohm’s law too with the four-current having onlyJ^{ϕ} andJ^{t} nonzero. The various physical parameters that have to correlate for possible equilibrium configurations are identified and their respective magnitudes estimated. It is found that for a given angular momentum distribution the inner edge of the disc can reach well within the usual6m limit only when the surface magnetic field of the central object is not too high when the matter density at the outer edge of the disc and the accretion rate are taken with reasonable limits
pp 67-72 March 1990
Estimation of the dissociation energy of CO^{+} from spectroscopic data
The potential energy curves for theX^{2} Σ^{+} andB^{2} Σ^{+} states of CO^{+} have been constructed by the Rydberg-Klein-Rees (RKR) method as modified by van der Sliceet al. The dissociation energy is estimated to be 7.70±0.19 eV by the method of curve fitting using the five parameter Hulburt-Hirschfelder’s function. The estimated value is in good agreement with the value (7.839 eV) given by Misraet al. Carefull observation of the results reveals that accurateD_{0} value for CO^{+} is 8.33 eV
pp 81-123 March 1990
An atlas of the optical spectrum of supernova 1987A in the large magellanic cloud
V. J. Mclntyre A. C. Gilmore J. B. Hearnshaw
Photographic spectra of SN1987A in the LMC have been obtained from 1987 February 25 to 1988 June 30. Microdensitometer tracings of these have been reduced to intensity and corrections for instrumental response have been applied to the spectra. This paper presents these data in an atlas format, discusses the reduction procedures in detail, and presents radial velocity measurements of selected lines in the spectra
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