Volume 13, Issue 4
December 1992, pages 287-347
pp 287-291 December 1992
There are indications now that globular clusters contain a large number of low magnetic field millisecond pulsars. Since millisecond pulsars are expected to emit γ-rays due to curvature radiation, it is likely that globular clusters will themselves be sources of γ-rays bright enough to be detectable by present day instruments. Using the expression derived by Scharlemann, Arons & Fawley (1978) of the energy acquired by the electrons moving along the open magnetic field lines of the pulsars we have calculated the likely luminosity of γ-rays from globular clusters. We discuss our results in the light of the calculations reported in the literature based on some of the other models.
pp 293-305 December 1992
We present the results from CCD photometry in theV, R andI bands, of the ‘Dipper Asterism’ region of the open cluster M67 based on observations carried out at the prime focus of the 2.3 m Vainu Bappu Telescope of the Vainu Bappu Observatory, Kavalur. The CCD parameters like the system gain and the readout noise are measured using several flatfield frames taken through the standardI filter. The CCD chip is calibrated using the photometric standards in the field and linear colour transformation relations are derived. Also a few newVRI photometric measurements are reported for the members of the cluster.
pp 307-318 December 1992
A detailed spectroscopic investigation of LR Sco which was earlier misclassified as R CrB star is made. Atmospheric parameters and elemental abundances are determined using detailed depth-dependent model atmospheres and line synthesis technique. Most of the elements show near solar abundances.
The strength of circumstellar components seen in Na D lines are used to derive the mass loss rate. Another independent estimate of mass loss rate is made using the observed infrared flux from 1–100Μm. These two approaches lead to nearly the same value of mass loss rate whenMvis assumed to be – 4.5 for this star.
pp 319-326 December 1992
A dynamical model composed of a disk galaxy with an elliptic companion, moving in a circular orbit, is used in order to study the stellar orbits in a binary galaxy. Using the Poincare surface of section we study the evolution of the stochastic regions in the primary galaxy considering the mass of the companion or the value of the Jacobi’s integral as a parameter. Our numerical calculations suggest that the regions of stochasticity increase, as the mass of the companion or the value of the Jacobi’s integral increase. An interesting observation is that only direct orbits become stochastic.
pp 327-347 December 1992
We present a method of a possible physical identification of the static and axially symmetric Weyl-type vacuum γ and nγ metrics. This method, in which no interior solutions of any kind are involved, is based on the comparison of the far-field forms of the γ and nγ metrics, and of the far-field form of the metric tensor due to a bounded gravitating perfect-fluid source given correctly to post-Newtonian accuracy. The parameters of the vacuum solutions are expressed in terms of physical parameters of a prolate fluid source, namely total mass-energy, semiaxes and eccentricity, defined consistently to post-Newtonian accuracy. The results, based on the otherwise arbitrary fluid source, appear physically general. Possible astrophysical candidates for the far-field γ andnγ metrics are proposed, based on the conditions imposed on them by the identification method. The advantages and deficiencies of the identification method are briefly discussed.
Volume 40 | Issue 2
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