IIA Institutional Repository: Recent submissions

  • Integrated parameters of open clusters 
    Pandey, A. K; Bhatt, B. C; Mahra, H. S; Sagar, R (Royal Astronomical Society, 1989-01)
    Integrated magnitudes and colors of population I synthetic clusters have been derived using theoretical evolutionary tracks and an age-dependednt initial mass function. A comparison of the theoretically obtained integrated ...
  • Stability of cool flux tubes in the solar chromosphere. II - Non-linear dynamical behaviour 
    Hasan, S. S; Kneer, F (The European Southern Observatory, 1990-06)
    A single vertical cool flux tube in the solar chromosphere is focused upon for stability studies. The analysis of a previous study by Hasan and Kneer (1986) is extended to the nonlinear regime with a view to examining the ...
  • Comments on the variability and physical parameters of the F supergiant Phi Cassiopeiae 
    Ferro, A. A; Parrao, L; Giridhar, S (Astronomical Society of the Pacific, 1988-08)
    UBVRI and uvby photometry and radial velocities have been obtained for the F0 Ia supergiant Phi Cas. The variability is confirmed from the radial velocities; the velocity range is small (Delta V/subr of about 6 km/s). No ...
  • Radial distribution of the integrated light and photometric colours in open star clusters 
    Sagar, R; Bhatt, H. C (Indian Academy of Sciences, 1989-06)
    Mass segregation in the form of preferential concentration of more massive stars in the central regions of a number of open star clusters has been known for some time. In this paper, integrated UBV colors in concentric ...
  • Is the X-ray pulsar H 0253 + 193 a neutron star spun down in a molecular cloud? 
    Bhatt, H. C (The European Southern Observatory, 1990-06)
    The detection of 206s X-ray pulsations from H0253+193 indicates that the source is a compact object. It is argued here that object can not be a T Tauri star or Be/X –ray binary pulsar suggested that H 0253+193 is slowly ...
  • Internal kinematics of open star clusters 
    Sagar, R; Bhatt, H. C (Royal Astronomical Society, 1989-02)
    Proper motion measurements are employed to investigate the internal kinematics of eight open star clusters. In most of the clusters considered, no dependence of the intrinsic dispersion in proper motion on stellar mass and ...
  • Dust envelopes around RV Tauri stars 
    Raveendran, A. V (The Royal Astronomical Society, 1989-06)
    In the IRAS (12)-(25), (25)-(60) color-color diagram, RV Tauri stars are found to populate cooler temperature regions, distinctly different from those occupied by the oxygen and carbon Miras. The IRAS fluxes are consistent ...
  • Is LR SCO and RCB star? 
    Giridhar, S; Kameswara Rao, N; Lambert, D. L (The Observatory, 1990-08)
  • Capture of field stars by molecular clouds 
    Bhatt, H. C (European Southern Observatory, 1989-04)
    Field stars can be captured by massive interstellar clouds. Stars encounter interstellar clouds with relative velocities that have a distribution. Close encounters in which stars enter a cloud with relative velocities less ...
  • Polarimetric observations of comet P/Halley on 19 March 1986 
    Sen, A. K; Joshi, U. C; Deshpande, M. R; Babu, G. S. D; Kulshrestha, A. K (European Southern Observatory, 1988-10)
    Optical linear polarization data are presented for the coma and tail region of comet P/Halley observed on 19 March 1986. Polarization in the continuum has been found to increase with wavelength while the position angle ...
  • Probability of arrival of rays of light for propagation through random media: Connection with rotational brownian motion 
    Chatterjee, S (Elsevier, 1989-12)
    An expression is derived for the probability of arrival of rays of light for propagation through a random medium with isotropic and homogeneous correlation function for the refractive index fluctuations. This expression ...
  • Rahu in the Burmese Tradition 
    Kochhar, R. K (Royal Astronomical Society, 1990-06)
  • JHK photometric study of the variable interstellar extinction in the direction of open star cluster NGC 654 
    Sagar, R; Yu, Q. Z (The Royal Astronomical Society, 1989-10)
    JHK magnitudes have been determined for 18 stars in the field of NGC 654. Study of the interstellar extinction law in the cluster direction indicates an anomalous distribution of interstellar grains causing more extinction ...
  • The R Coronae Borealis stars: carbon abundances from forbidden carbon lines 
    Pandey, G; Lambert, D. L; Kameswara Rao, N; Gustafsson, B; Ryde, N; Yong, D (Royal Astronomical Society, 2004-09)
    Spectra of several R Coronae Borealis (RCB) stars at maximum light have been examined for the [CI] 9850- and 8727-Åabsorption lines. The 9850-Åline is variously blended with an FeII and CN lines, but positive identifications ...
  • Effects of stimulated emission on radiative transfer with partial redistribution 
    Rangarajan, K. E; Mohan Rao, D; Peraiah, A (The European Southern Observatory, 1990-08)
    The non-LTE line transfer with stimulated emission is studied. Stimulated emission is important for red transitions in hot stars and infrared transitions in cool stars. The deviation of the absorption and emission profiles ...
  • The Gauribidanur radio observatory 
    Sastry, Ch. V (National Institute of Science Communication and Information Resources, 1989-08)
    The Raman Research Institute and the Indian Institute of Astrophysics in a joint collaboration program operate the Gauribidanur radio observatory. Details of the various antenna arrays and receiver systems available at the ...
  • Optical telescopes in India 
    Bhattacharyya, J. C (National Institute of Science Communication and Information Resources, 1989-08)
    Fabrication and use of optical telescopes for astronomical observations in India have been reviewed. Evolution of telescopes, their optics, mounting and drive system leading to large aperture instruments of today has been ...
  • Near-infrared photometric study of open star cluster IC 1805 
    Sagar, R; Yu, Q. Z (American Astronomical Society, 1990-04)
    The JHK magnitudes of 29 stars in the region of open star cluster IC 1805 were measured. These, and the existing infrared and optical observations, indicate a normal interstellar extinction law in the direction of the ...
  • Loss of magnetic tension in pre-flare magnetic configurations 
    Venkatakrishnan, P (Kluwer Academic Publishers, 1990-08)
    We demonstrate that magnetic tension vanishes at regions of large magnetic shear on the polarity inversion line. The characteristics of these tension-free fields depend on the density of the medium and, therefore, change ...
  • Study of young open clusters as tracers of spiral features in our Galaxy. IV - Czernik 20 (OC1 427) 
    Babu, G. S. D (Indian Academy of Sciences, 1989-09)
    Photoelectric and photographic photometry of 72 stars was done in the field of the not-well-studied open cluster Czernik 20 in the direction of the Auriga constellation. Of these stars, a total of 43 have been found to be ...

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