• Volume 4, Issue 1

March 1983,   pages  1-63

• Scanner observations of the classical cepheids RT Aur and T Vul

The effective temperatures of the classical Cepheids RT Aur and T Vul have been determined by a comparison of their spectral scans with appropriate model atmospheres. The radii of the stars have been determined through the Wesselink method. Using these temperatures and the Wesselink radii, the luminosities of the stars have been determined. These radii estimates, including the radii of SU Cas (Joshi & Rautela 1980) andζ Gem (unpublished) fit better in the theoretical period-radius relationship given by Cogan (1978), as compared to earlier determinations of Wesselink radii. The pulsation masses and evolutionary masses of the stars have been calculated. The pulsation to evolutionary mass ratio is derived to be 0.85.

Based on the effective temperatures obtained by us at different phases of the stars aθc − (B-V)0 relationship is found of the form,$$\begin{gathered} \theta _e = 0.274 (B - V)_0 + 0.637 \hfill \\ \pm 0.011 \pm 0.007 \hfill \\ \end{gathered}$$

• Reflection effect in close binaries. II. Distribution of emergent radiation from the irradiated component along the line of sight

We have calculated the effects of irradiation from a point source observed at infinity. Plane-parallel approximation and spherically-symmetric approximations are employed in calculating the self-radiation field for the sake of comparison. It is found that there are considerable changes in the radiation received at infinity between the approximation of plane-parallel stratification and spherical symmetry.

• Spectroscopic binaries near the north Galactic pole paper 7: HD 107742

Photoelectric radial-velocity measurements show that HD 107742 is a spectroscopic binary with a period of 875 days and a small (but definitely non-zero) eccentricity. The star is not a member of the Coma Cluster, against which it is seen projected.

• Spectroscopic binaries near the north Galactic pole paper 8: HD 121844

Photoelectric radial-velocity measurements show that HD 121844 is a spectroscopic binary with a period of 303 days, a high eccentricity (0.49) and a high negative γ-velocity (- 61 km s-1).

• Intensity and polarization line profiles in a semi-infinite Rayleigh-scattering planetary atmosphere. II. Variations of equivalent width over the disk

The study of the variation of equivalent width in a Rayleighscattering planetary atmosphere along the intensity equator and along the mirror meridian on whichμ =μ0 shows that the equivalent widths decrease monotonically towards the poles, the limb and the terminator with the following characteristics: (i) the weakest lines exhibit the maximum change; (ii) theIer component shows more change than theIer component; (iii) the decrease towards the limb or the terminator is not as sharp as that towards the poles; (iv)Ier component shows more decrease towards the limb whileIer component shows more decrease towards the terminator; and (v) the relationW (μ, φ;μ0,φ0)= W (μ0,φ0;μ, φ) holds for the total intensity. These results are qualitatively in agreement with the observations of absorption bands in the spectra of Venus, Jupiter and Saturn.

• Intensity and polarization line profiles in a semi-infinite Rayleigh-scattering planetary atmosphere. III. Variation of polarization profiles and the Stokes parameter Q over the disk

The variation of the polarization profiles, the Stokes parameters Q andU, and the angle defining the plane of polarization along the intensity equator and along the mirror meridian, on whichμ = μ0, in a Rayleighscattering atmosphere is studied. It is found that these variations are more complex than thought hitherto, particularly at large phase angles.

• Diffuse radio emission from the Coma cluster of galaxies at decametre wavelengths

We have observed the region of the Coma cluster at 34.5 MHz with a resolution of 26 arcmin × 40 arcmin. A map of the diffuse halo (Coma C) is presented. The size of the halo is found to be 54 arcmin × 30 arcmin. The position angle is 50° ± 10° and the integrated flux is 60 ± 11 Jy.

We have also found an extended source to the south of Coma A. The measured half-power widths of this source are 30 arcmin × 40 arcmin. The position angle is 135° and the integrated flux is ~ 15 Jy at 34.5 MHz. The spectral index in the frequency range 408 to 34.5 MHz is -1.0. It is suggested that this source also belongs to the Coma cluster.

• Astrophysical molecules of AlH and CaH: RKR potential and dissociation energies

The true potential energy curves for the electronic ground states of astrophysically important AlH and CaH molecules are constructed by the Rydberg-Klein-Rees method. Empirical potential functions, of three-parameters by Lippincott, of five-parameters by Hulburt and Hirsch-felder and, of electronegativity by Szöke and Baitz, are examined for the adequacy to represent the true curve. From the best-fitting function, the dissociation energiesD00 of AlH and CaH molecules are estimated to be 2.99 ± 0.08 and 2.72 ± 0.06 eV respectively. The force constants indicate that these values are of correct magnitude.

• Ultraviolet variability of HD 62001 – The central star of the missing nebula V-V 1-7

IUE observations of HD 62001 do not confirm the ultraviolet variability of 0.15 mag seen from the ANS observations. These intriguing variations in ANS observations seem to be caused by a nearby (∼ 70 arcsec away) B star getting in and out of the field of view of the telescope, which had a jitter of 20 arcsec. There seems to be no evidence for the presence of a hot companion, either from the energy distribution or from UV variability. However, visual light variations are present. This, coupled with the radial velocity variations, indicates a binary nature probably of Algol type.

• # Journal of Astrophysics and Astronomy

Current Issue
Volume 40 | Issue 3
June 2019

• # 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.