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Browsing by Subject "Stars: AGB and Post-AGB"

Browsing by Subject "Stars: AGB and Post-AGB"

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  • Abundance analyses of cool extreme helium stars 
    Pandey, G; Kameswara Rao, N; Lambert, D. L; Jeffery, C. S; Asplund, M (Royal Astronomical Society, 2001-07)
    Extreme helium stars (EHes) with effective temperatures from 8000 to 13000K are among the coolest EHes and overlap the hotter R CrB stars in effective temperature. The cool EHes may represent an evolutionary link between ...
  • Abundances in planetary nebulae: Mz 3 
    Pottasch, S. R; Surendiranath, R (EDP Sciences, 2005-12)
    ISO spectra of the bipolar planetary nebula Mz 3 are used to determine the element abundances in the bright lobes of the nebula. The ISO spectra alone are sufficient to determine nitrogen, neon, argon, sulfur and iron ...
  • BVRIJHK photometry of post-AGB candidates 
    Fujii, T; Nakada, Y; Parthasarathy, M (E D P Sciences, 2002-04)
    BVRIJHK photometric observations are presented for 27 post-AGB candidates. Almost all objects show a double peaked SED curve in the optical to far-infrared wavelengths. Seventeen objects were classified as post-AGB stars ...
  • Chemical composition of HD 179821 (IRAS 19114+0002) 
    Thévenin, F; Parthasarathy, M; Jasniewicz, G (European Southern Observatory, 2000-07)
    A LTE analysis of medium resolution spectra of HD 179821 has been made. Derived atmospheric parameters of HD 179821 are K, and [Fe/H]=-0.5. The position of the star in the H-R diagram, its high radial velocity (Vr=100 ...
  • The Chemical Compositions of the SRD Variable Stars. III. KK Aquilae, AG Aurigae, Z Aurigae, W Leo Minoris, and WW Tauri 
    Giridhar, S; Lambert, D. L; Gonzalez, G (The Astronomical Society of the Pacific, 2000-12)
    Chemical compositions are derived from high-resolution spectra for five field SRd variables. These supergiants not previously analyzed are shown to be metal poor: KK Aql with [Fe/H]=-1.2, AG Aur with [Fe/H]=-1.8, Z Aur ...
  • Do hydrogen-deficient carbon stars have winds? 
    Geballe, T. R; Kameswara Rao, N; Clayton, G. C (Institute of Physics, 2009-06)
    We present high resolution spectra of the five known hydrogen-deficient carbon (HdC) stars in the vicinity of the 10830 Å line of neutral helium. In R Coronae Borealis (RCB) stars the He I line is known to be strong and ...
  • FG Sagittae: A Newborn R Coronae Borealis Star? 
    Gonzalez, G; Lambert, D. L; Wallerstein, G; Kameswara Rao, N; Smith, V. V; McCarthy, J. K (The American Astronomical Society, 1998-01)
    We have monitored FG Sge's spectroscopic changes since the time just prior to its dramatic fading in 1992 August. The most significant qualitative changes in the spectrum include large variations in the strength of the C2 ...
  • High resolution spectroscopy of the high latitude rapidly evolving post-AGB star SAO 85766 (= IRAS 18062+2410) 
    Parthasarathy, M; García-Lario, P; Sivarani, T; Manchado, A; Sanz Fernández de Córdoba, L (European Southern Observatory, 2000-05)
    SAO 85766 (b = +20o) is an IRAS source with far-infrared colours similar to planetary nebulae. According to the HDE catalogue, its spectrum in 1940 was that of an A5 star. The UV fluxes and colours derived from data obtained ...
  • Low resolution spectroscopy of hot post-AGB candidates 
    Parthasarathy, M; Vijapurkar, J; Drilling, J. S (EDP Sciences, 2000-08)
    Spectral types are determined from low resolution optical spectra of 40 IRAS sources with far-infrared colours similar to planetary nebulae. The presence of circumstellar dust, high galactic latitude, and early supergiant ...
  • Polarization Measurements of Post-Asymptotic Giant Branch Candidates and Related Stars 
    Parthasarathy, M; Jain, S. K; Sarkar, G (The American Astronomical Society, 2005-05)
    We have obtained UBVRI polarization measurements of 26 post-asymptotic giant branch (post-AGB) candidates and related stars. The extremely metal-poor post-AGB star HR 4049 has been observed several times. In most cases we ...
  • Probing the mass-loss history of the yellow hypergiant IRC+10420 
    Dinh, V. T; Muller, S; Lim, J; Kwok, S; Muthu, C (The American Astronomical Society, 2009-05-20)
    We have used the submillimeter array to image the molecular envelope around the yellow hypergiant IRC+10420. Our observations reveal a large and clumpy expanding envelope around the star. The molecular envelope shows a ...
  • The UV (IUE) spectrum of the planetary nebula PC 11 (HD 149427) 
    Parthasarathy, M; García-Lario, P; Pottasch, S. R; de Martino, D; Surendiranath, R (European Southern Observatory, 2000-03)
    The UV spectrum of PC 11 is found to show variations in the strength of the O III] 1666Å , N III] 1750Å and C III] 1909Å emission lines. The detection of continuum emission in the wavelength interval 2650Å to 3200Å indicates ...

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