• Volume 6, Issue 1

      March 1985,   pages  1-75

    • Editorial

      V. Radhakrishnan

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    • Tidal interactions in binary stellar systems

      S. M. Alladin N. Ramamani T. Meinya Singh

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      The tidal interactions in binary stellar systems are studied under the assumption that the orbital motion of the binary is negligible in comparison with the stellar motion. By integrating over time the tidal forces acting on the stars, the energy changes are derived. These are used to obtain simple analytical expressions for the rates of disruption and merging. This method gives appropriate value for the Roche density ρr and it is found that the disruption rate of a satellite of density ρ changes drastically at ρ ρR A comparison is made with earlier results obtained under the simplifying assumption that stellar motion is negligible in comparison with the orbital motion of the binary and its implications are discussed.

    • Nonlinear development of convective instability within slender flux tubes. II. The effect of radiative heat transport

      P. Venkatakrishnan

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      Inclusion of radiative heat transport in the energy equation for a slender flux tube leads to oscillations of the tube. The amplitude of the oscillations depends on the radius of the tube when lateral heat exchange alone is considered. Longitudinal heat transport has a greater influence on the evolution of the instability than lateral heat exchange for the particular value of tube radius considered in the calculation. Heat transport is seen to reduce the efficiency of concentration of magnetic fields by convective collapse in the case of polytropic tubes.

    • Interstellar scintillation measurements of pulsars at 326.5 MHz

      V. Balasubramanian S. Krishnamohan

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      We have measured the decorrelation frequency (fv) and decorrelation time (tv) for 15 pulsars. We show by combining our data with those of others thatfv∫ DM-1.79±0.14 andtv∫ DM-0.80±0.15 up to a dispersion measure (DM) of about 60 cm3 pc. The combined data set does not form a complete sample, but the relations obtained from our measurements on 14 pulsars, which form almost a complete sample up to 41 cm3 pc, are consistent with the above relations, suggesting that these relations are not seriously affected by selection effects. The relations are broadly in agreement with those expected from a homogeneous interstellar medium and are in disagreement with earlier conclusions by others that these relations steepen even for low-DM pulsars. The agreement suggests that the local interstellar medium is homogeneous at least up to a distance of about 2 kpc.

    • An X-ray hubble diagram for quasi-stellar objects

      A. K. Sapre V. D. Mishra

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      To form the Hubble diagram for quasi-stellar objects (QSOs),we have made use of the recently published data on X-ray fluxes of 159 QSOs observed from the Einstein Observatory. The scatter in the Hubble diagram and the lack of an obvious redshift-flux density correlation for these QSOs have been attributed to the observational selection effect that the intrinsically less luminous QSOs can be detected only in the nearby region of space. When the optical, radio and X-ray selection effects are removed, keeping only the intrinsically brighter sources, we obtain a sample of 16 QSOs having a small dispersion in X-ray luminosities (〈 logLx〉) = 46.12 ± 0.28), a statistically significant linear correlation between (logfx, logcz) pairs and a slopeA =-1.906 ± 0.061 of the linear regression oflog fx on logcz. This slope is consistent, at a confidence level of 95 per cent or greater, with the slope of-2.0 expected theoretically based on the assumption that the redshifts of QSOs are cosmological in nature.

    • A study of solar modulation of medium energy primary cosmic ray nuclei

      Projit K. Das T. D. Goswami

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      The energy spectra of primary cosmic rays were studied in the energy interval 150 to 450 MeV/nucl by using balloon-borne cellulose-nitrate solid-state plastic detector. Effects of solar modulation were studied using the theoretical spectrum ofH1 nuclei near the solar minimum in 1964 as the demodulated spectrum. The ‘force-field’ potential which fit the experimental results was estimated to be 270 MeV/nucl.

    • A study of the open cluster NGC 2374

      G. S. D. Babu

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      The results of modified objective grating observations and photoelectric as well as photographic photometry of the open cluster NGC 2374 are presented. The cluster contains at least twenty stars as definite members down tomv ≈ 15mag. There is a uniform extinction ofE(B - V) = 0.175 mag and the distance is 1.2 ± 0.1 kpc. The most likely age of this cluster is 7.5 ×107 years.

    • Spectroscopic binaries near the north galactic pole - Paper 11: HD 105982

      R. F. Griffin

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      Photoelectric radial-velocity measurements show that HD 105982 is a spectroscopic binary with a period of 3.7 years.

    • Corrigendum

      J. V. Narlikar

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  • Journal of Astrophysics and Astronomy | News

    • 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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