IIA Institutional Repository: Recent submissions

  • Solar eclipses during 1868-1980 in which Madras, Kodaikanal Observatories and IIA participated 
    Birdie, C; Vagiswari, A (Indian Institute of Astrophysics, 2009-06)
    Participation in solar eclipse studies have been a notable characteristics of the institute for more than a century. For all major eclipses teams were sent and the expedition met with a considerable degree of success. ...
  • Origin of spatial variations of scattering polarization in the wings of the Ca I 4227 Å line 
    Sampoorna, M; Stenflo, J. O; Nagendra, K. N; Bianda, M; Ramelli, R; Anusha, L. S (The American Astronomical Society, 2009-07-10)
    Polarization that is produced by coherent scattering can be modified by magnetic fields via the Hanle effect. This has opened a window to explorations of solar magnetism in parameter domains not accessible to the Zeeman ...
  • BVRIJHK photometry of post-AGB candidates: evolution of post-AGB central stars 
    Fujii, T; Nakada, Y; Parthasarathy, M (Kluwer Academic Publishers, 2001-08)
    Post-AGB stars are generally believed to be on their way to the planetary nebula stage. However, there has been a question about the evolutionary path for the low-mass ones. We present BVRIJHK photometry of post-AGB ...
  • Identification of emission bands in P/Halley 
    Bhattacharyya, J. C; Babu, G. S. D; Ghosh, K. K; Jayakumar, K; Appakutty, M (Indian Academy of Sciences, 1986)
    Spectrophotometric studies of P /Halley (r = 1.98 AU, Δ= 1.19AU, r = 1.97, Δ = 1.16 AU and r = 1.95 AU, Δ. = 1.13 AU) in the spectral range 3900 A - 6450 A were made on three nights and identifications of emission features ...
  • The evolutionary status of HD 179821 
    Thévenin, F; Jasniewicz, G; Parthasarathy, M (Kluwer Academic Publishers, 2001-08)
    HD 179821 (IRAS 19114+0002) is classified as a moderately metal-poor ([Fe/H] = - 0.5) post-AGB star of Teff = 5660 K and also as a very massive supergiant of Teff = 6750 K. Recent detailed studies of this star are not able ...
  • The effect of strong magnetic fields on acoustic power in their surroundings at the surface of the sun 
    Nicholas, C. J; Thompson, M. J; Rajaguru, S. P (European Space Agency, 2004-10)
  • Outer rings of Saturn 
    Bhattacharyya, J. C; Vasundhara, R (Indian Academy of Sciences, 1985)
    A two component model of a possible ring structure at about 12.5 Saturn radii is presented here which can explain the shapes of the immersion and emersion occultation profiles obtained during the occultation of SAO 158913 ...
  • Application of local-area helioseismic methods as predictors of space weather 
    Jensen, J. M; Lundstedt, H; Thompson, M. J; Pijpers, F. P; Rajaguru, S. P (European Space Agency, 2004-10)
    Space weather is growing concern to our increasingly technological society. Here we discuss neural-network approaches to forecasting space weather, in which we plan to incorporate now-cast information about solar sub-surface ...
  • Comparison of GONG and MDI sound-speed anomalies beneath two active regions 
    Hughes, S. J; Rajaguru, S. P; Thompson, M. J (European Space Agency, 2004-10)
    Travel times of acoustic waves are calculated from Dopplergrams of solar oscillations obtained using the Global Oscillation Network Group (GONG) ground-based network and the Michelson Doppler Imager (MDI) instrument on ...
  • Spectroscopy of HD 168625 (IRAS 18184-1623) 
    García, L. P; Sivarani, T; Parthasarathy, M; Manchado, A (Kluwer Academic Publishers, 2001-08)
    HD 168625 (B9-A0 Ia) was classified as a post-AGB star and also as a luminous blue variable. We have analysed the high resolution optical spectra of HD 168625 and derived the atmospheric parameters and the chemical ...
  • Spectroscopy of post-AGB candidate IRAS 10215-5916 
    Sivarani, T; Parthasarathy, M; García, L. P; Manchado, A (Kluwer Academic Publishers, 2001-08)
    IRAS 10215-5916 was classified as a post-AGB star and also as a massive red supergiant. It was also found to be a spectroscopic binary. In our high resolution spectra we found molecular features from a cool star of Teff = ...
  • Spectroscopy of post-AGB candidate HD 331319 (IRAS 19475+3119) 
    Sivarani, T; Parthasarathy, M; García, L. P; Manchado, A (Kluwer Academic Publishers, 2001-08)
    HD 331319 is a F3 Ib star with a detached cold circumstellar dust shell with far-IR colours similar to planetary nebulae. From an analysis of high resolution spectra using LTE stellar atmospheric models, we have derived ...
  • Spectroscopy of post-AGB a-supergiant HD 101584 (IRAS 11385-5517) 
    Sivarani, T; Parthasarathy, M; García, L. P; Manchado, A; Pottasch, S. R (Kluwer Academic Publishers, 2001-08)
    In the high resolution optical spectra we identified forbidden lines of [OI] and [CI], which indicate the presence of low excitation nebula. There are many emission lines due forbidden and permitted lines of neutral and ...
  • Light variability of color selected IRAS sources: variables in late AGB and early post-AGB phase 
    Fujii, T; Nakad, Y; Parthasarathy, M (Kluwer Academic Publishers, 2001-08)
    The transition from AGB to post-AGB stars was investigated using the H-band monitoring of these objects for four years. The Mira-type pulsations were found only in the restricted area in the IRAS two color diagram. The ...
  • Multislit spectrophotometry of the corona 
    Saxena, A. K; Singh, J; Gabriel, F (Indian National Science Academy, 1981)
  • Ionospheric electron content and equivalent slab thickness in the equatorial region 
    Das Gupta, A; Basu, S; Bhar, J. N; Bhattacharyya, J. C (American Geophysical Union, 1975-02)
    The ionospheric total electron content and equivalent slab thickness in the equatorial region around 75° E have been studied. It is found that the slab thickness exhibits a strong latitudinal dependence with a maximum at ...
  • Coronal photography at H alpha 
    Rangarajan, K. E; Giridhar, S (Indian National Science Academy, 1981)
  • Spectrophotometry of the inner corona 
    Rajamohan, R; Raheem, K. C. A; Jayarajan, A. P (Indian National Science Academy, 1981)
  • HiRES: high resolution extreme ultraviolet spectroheliometer 
    Berger, T; Bergamini, P; Kirby, H; Timothy, J. G; Walker, A. B. C; Bhattacharyya, J. C; Jain, S. K; Saxena, A. K; Huber, M. C. E; Naletto, G; Tondello, G (Cambridge University Press, 1993)
    The HiRES sounding rocket payload is designed to obtain very high spatial, spectral, and temporal resolution images of the solar chromospheric and coronal plasmas in the extreme ultraviolet (EUV) wavelength range from 500 ...
  • Determination of the limb darkening of the solar disc in the visible and near ultraviolet 
    Bhattacharyya, J. C; Chandramohan, R; Sundareswaran, A; Charles, A (Indian National Science Academy, 1981)

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