• Volume 10, Issue 3

      September 1989,   pages  237-346

    • The 1985 outburst of RS Ophiuchi: Spectroscopic results

      G. C. Anupama T. P. Prabhu

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      Optical spectroscopic data on the recurrent nova RS Ophiuchi obtained between 32 and 108 days after its last outburst on 1985 January 27 are presented. RS Oph was in the coronal-line phase at that time. The widths of the permitted as well as coronal-lines decreased continuously. Assuming that the ejected envelope decelerated due to its interaction with circum stellar matter, its size is deduced as a function of time. Observed fluxes in permitted lines would then imply that the electron density decreased from 3 × 109 cm#x2212;3 on day 32 to 1.8 × 108 cm-3 on day 108, for an assumed filling factor of 0.01. The helium abundance in the ejecta is estimated to be n(He)/n(H) ∼ 0.16. The mass of the unshocked ejecta was 3 × 10-6 (Φ/0.01)1/2 M, (at this stage, where f is the filling factor. Observed fluxes in coronal-lines imply that the temperature of coronal-line region decreased from 1.5 × 106 K on day 32 to 1.1 × 106 K on day 108. Most of the coronal line emission, as well as He n emission arises in shocked and cooling ejecta. This region is not isothermal, but contains material at a wide range of temperatures. Mass of the shocked ejecta is estimated to be in the range 10−7−10−6 M⊙ Based on the number of H- and He-ionizing photons, we estimate that the ionizing source evolved from a radius and temperature of (2 × l012 cm, 3 × 104 K) on day 32 to (6 × l09 cm, 3.6 × 105K) on day 204.

      We also present the spectra of RS Oph recorded in quiescent phase, 2 and 3 years after outburst, for comparison. The spectrum is dominated by that of M2 giant secondary, with superposed emission lines of H and He I

    • Planetary distance law and resonance

      J. J. Rawal

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      The relation between the planetary distance law and the resonant structures in the solar system and in the satellite systems is shown, in that, the resonance relation has been expressed in terms of Roche’s (Bode’s) constant defined in the text. This brings forth a coherent, elegant and unified picture of the formation and structure of the solar system and the satellite systems. The Roche’s (Bode’s) constant is seen to play a central role in this unified picture, in that, it also appears to govern the resonance phenomenon in the systems

    • Multiple shocks in the rotating winds from self-gravitating discs

      Sandip K. Chakrabarti

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      We present the analytic theory of dissipative and non-dissi-pative shocks in the rotating outflows in both the pseudo-Newtonian and the Schwarzschild geometry. We include the effects of the self gravity of the surrounding massive disc and show that the flow may have as many as five critical points when the angular momentum and the disc mass are sufficiently high. This leads to the possibility of the multipleannular shocks within the flow. We derive the expressions correlating the pre-shock and the post-shock quantities for all the three principal types of discontinuities. From these relations it is shown that for given initial flow parameters such as the angular momentum and the energy there could be as many as eighteen formal shock locations out of which at most two are chosen in reality. Detailed classification of the parameter space in terms of the initial flow parameters will be discussed elsewhere

    • Undamped oscillations of collisionless stellar systems: Spheres, spheroids and discs

      S. Sridhar R. Nityananda

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      The collisionless Boltzmann equation governing self-gravitating systems such as galaxies has recently been shown to admit exact oscillating solutions with planar and spherical symmetry. The relation of the spherically symmetric solutions to the Virial theorem, as well as generalizations to non-uniform spheres, uniform spheroids and discs form the subject of this paper. These models generalize known families of static solutions. The case of the spheroid is worked out in some detail. Quasiperiodic as well as chaotic time variation of the two axes is demonstrated by studying the surface of section for the associated Hamiltonian system with two degrees of freedom. The relation to earlier work and possible implications for the general problem of collisionless relaxation in self gravitating systems are also discussed

    • Study of young open clusters as tracers of spiral features in our galaxy. Paper 4: Czernik 20 (OCl 427)

      G. S. D. Babu

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      Photoelectric and photographic photometry of 72 stars was done in the field of the not-well-studied open cluster Czernik 20= OCl 427 in the direction of the Auriga constellation. Of these stars, a total of 43 have been found to be probable members down tomv− 15.75 mag. There is apparently a variable extinction across the field of the cluster withE(B-V) ranging from 0.53 to 0.38 mag. The cluster stars show a range in their ages from 1.0 × 107 to 7.1 × 107 years, indicating that Czernik 20 is young enough to be considered as a spiral-arm tracer in the study of our Galaxy. The distance of this cluster is found to be 4.27 ±0.14 kpc and it is located inside the outer Perseus arm of the Milky Way

    • Orbital elements of the RS CVn eclipsing binary, SV Camelopardalis

      C. V. S. R. Sarma M. B. K. Sarma N. B. Sanwal

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      The extensiveUBV observations of SV Camelopardalis by Patkos (1982) have been analysed to derive the orbital elements of the system. The data were corrected for the effect of third body (Sarma, Sarma & Abhyankar 1985) and for the ‘RS CVn’ distortion wave (Sarma, Vivekanandarao & Sarma 1988). The cleaned data were used to obtain a preliminary solution by a modified version of Wellmann method (Sarma & Abhyankar 1979) from which we concluded that the primary eclipse is a transit. The final orbital elements of SV Cam were obtained by the modified version (Sarma 1988; Sarmaet al. 1987) of WINK program by Wood (1972). The colour and median brightness variation are discussed. From the spectroscopic mass functionf(m) = 0.118 M (Hiltner 1953), the absolute dimensions of the components are found to be 0.826 Mbd & 0.592 M and 1.236 R & 0.778 R for the primary and secondary components, respectively. The age of the binary system is estimated to be 6.0 ± 1.0 × 108 years

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    • Continuous Article Publication

      Posted on January 27, 2016

      Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

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