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Browsing by Author "Lambert, D. L"

Browsing by Author "Lambert, D. L"

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  • 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 ...
  • Fluorine detection in hot extreme helium stars 
    Bhowmick, A; Pandey, G; Lambert, D. L (Springer, 2020-12)
    The origin and evolution of hydrogen-deficient stars are not yet adequately understood. Their chemical peculiarities, along with hydrogen-deficiency, makes them stand out from the rest and sheds light on their possible ...
  • Fluorine in R Coronae Borealis Stars 
    Pandey, G; Lambert, D. L; Kameswara Rao, N (Astronomical Society of the Pacific, 2008)
    Neutral fluorine lines are identified in the optical spectra of several R Coronae Borealis stars (RCBs) at maximum light. These lines provide the first measurement of the fluorine abundance in these stars. Fluorine is ...
  • Fluorine in R Coronae Borealis Stars 
    Pandey, G; Lambert, D. L; Kameswara Rao, N (University of Chicago Press, 2008-02)
    Neutral fluorine (F i) lines are identified in the optical spectra of several R Coronae Borealis stars (RCBs) at maximum light. These lines provide the first measurement of the fluorine abundance in these stars. Fluorine ...
  • Galactic chemical evolution and chemical tagging with open clusters 
    Reddy, A. B. S; Giridhar, S; Lambert, D. L (Indian Academy of Sciences, 2020-12)
    The article presents the consolidated results drawn from the chemical composition studies of Reddy et al. (2012, 2013, 2015, 2016) and Reddy & Lambert (2019), who through the high-dispersion echelle spectra (R=60000) of ...
  • The galactic R coronae borealis stars and the final he-shell flash object V4334Sgr (Sakurai’s object): a comparison 
    Hema, B. P; Pandey, G; Lambert, D. L (Proceedings of Science, 2012-08)
    The high resolution optical spectra of H-deficient stars, R Coronae Borealis stars and H-deficient carbon stars are analyzed by synthesizing the C2 Swan bands (0,1), (0,0), and (1,0) using our detailed line-list and ...
  • The Galactic R Coronae Borealis Stars: The C2 Swan Bands, the Carbon Problem, and the 12C/13C Ratio 
    Hema, B. P; Pandey, G; Lambert, D. L (IOP Publishing, 2012-03-10)
    Observed spectra of R Coronae Borealis (RCB) and hydrogen-deficient carbon (HdC) stars are analyzed by synthesizing the C2 Swan bands (1, 0), (0, 0), and (0, 1) using our detailed line list and the Uppsala model atmospheres. ...
  • A high resolution spectroscopic study of XX Ophiuchi 
    Goswami, A; Kameswara Rao, N; Lambert, D. L (Astronomical Society of India, 2001)
    The star XX Oph has been known to exhibit peculiar spectral variabilities since the work of Merrill in 1924. A high resolution spectroscopic study of the XX Oph spectra taken in July 1996 and later in June 1997 also exhibit ...
  • High Resolution Spectroscopy of QY Sge 
    Kameswara Rao, N; Goswami, A; Lambert, D. L (Astronomical Society of India, 2002-09)
    High resolution spectral analysis of QY Sge, a post AGB star is presented here. The spectrum of QY Sge is characterized by three major components: absorption lines representative of a G supergiant, sharp emission lines ...
  • High resolution spectroscopy of R Coronae Borealis during the 1988-1989 minimum 
    Lambert, D. L; Kameswara Rao, N; Giridhar, S (Indian Academy of Sciences, 1990-12)
    Moderate-resolution spectra of the C2 Swan 0-1 bandhead, the Na I D lines and the K I resonance lines near 7660 A obtained at minimum light during the 1988-1989 decline of R CrB are discussed and interpreted in terms of a ...
  • High resolution spectroscopy of the R Coronae Borealis star, V854 Centauri, during a deep minimum 
    Kameswara Rao, N; Lambert, D. L (American Astronomical Society, 1993-05)
    The R Coronae Borealis star V854 Cen was observed at minimum light (V about 15) at high spectral resolution from 5480 to 7070 A. The spectrum consists of three components: a continuum devoid of photospheric lines, a ...
  • High Resolution Spectroscopy of the Semi-Regular Variable LR Sco 
    Giridhar, S; Kameswara Rao, N; Lambert, D. L (Indian Academy of Sciences, 1992)
    A detailed spectroscopic investigation of LR Sco which was earlier misclassified as R CrB star is made. Atmospheric parameters and elemental abundances are determined using detailed depth-dependent model atmospheres and ...
  • High-resolution Optical Spectroscopy of DY Cen: Diffuse Interstellar Bands in a Proto-fullerene Circumstellar Environment? 
    Garcia-Hernandez, D. A; Kameswara Rao, N; Lambert, D. L (IOP Publishing, 2012-11-01)
    We search high-resolution and high-quality VLT/UVES optical spectra of the hot R Coronae Borealis star DY Cen for electronic transitions of the C60 molecule and diffuse interstellar bands (DIBs). We report the non-detection ...
  • High-Resolution Optical Spectroscopy of the R Coronae Borealis Star V532 Ophiuchi at Maximum Light* 
    Kameswara Rao, N; Lambert, D. L; Woolf, V. M; Hema, B. P (IOP Publishing, 2014-09)
    High-resolution optical spectra of the R Coronae Borealis (RCB) star V532 Oph at light maximum are discussed. The absolute visual magnitude M V of the star is found to be 4 : 9 0 : 5 . The elemental ...
  • A high-resolution spectroscopic analysis of the suspected spectroscopic binary HD 165553 
    Goswami, A; Kameswara Rao, N; Lambert, D. L (The Observatory, 2004-02)
    The results of an analysis of a high-resolution spectrum of the possible spectroscopic binary HD 165553, obtained with a spectral resolving power of ~ 60 000, are presented. A detailed chemical-composition study indicates ...
  • High-resolution spectroscopy of QY Sge: an obscured RV Tauri variable? 
    Kameswara Rao, N; Goswami, A; Lambert, D. L (Blackwell Publising Ltd, 2002-07)
    The first high-resolution optical spectra of QY Sge are presented and discussed. Menzies & Whitelock, on the basis of photometry and low-resolution spectra, suggested that this G0I supergiant was obscured by dust and seen ...
  • High-resolution spectroscopy of R CrB - pulsations, shells and mass loss 
    Kameswara Rao, N; Lambert, D. L (The Royal Astronomical Society, 1997-01)
    High spectral resolution observations obtained in 1994 and spanning three pulsation cycles of R CrB are discussed along with available UBV photometric observations for the same epochs. Model atmosphere based analyses of ...
  • High-resolution spectroscopy of the R Coronae Borealis and Other Hydrogen Deficient Stars 
    Kameswara Rao, N; Lambert, D. L (Springer, 2010)
    High-resolution spectroscopy is a very important tool for studying stellar physics, perhaps, particularly so for such enigmatic objects like the R Coronae Borealis and related Hydrogen deficient stars that produce carbon ...
  • High-resolution spectroscopy of the R Coronae Borealis star V Coronae Australis 
    Kameswara Rao, N; Lambert, D. L (Blackwell Synergy, 2008-02)
    Optical high-resolution spectra of the R Coronae Borealis star V CrA at light maximum and during minimum light are discussed. Abundance analysis confirms previous results showing that V CrA has the composition of the small ...
  • High-resolution spectroscopy of V854 Cen in decline - absorption and emission lines of C2 molecules 
    Kameswara Rao, N; Lambert, D. L (Royal Astronomical Society, 2000-04)
    High-resolution optical spectra of the R Coronae Borealis (RCB) star V854 Centauri in the early stages of a decline show, in addition to the features reported for other RCBs in decline, narrow absorption lines from the C2 ...

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