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Browsing by Author "Lambert, D. L"

Browsing by Author "Lambert, D. L"

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  • The Chemical Compositions of the SRD Variable Stars. II. WY Andromedae, VW Eridani, and UW Librae 
    Giridhar, S; Lambert, D. L; Gonzalez, G (The Astronomical Society of the Pacific, 1999-10)
    Chemical compositions are derived from high-resolution spectra for three stars classed as SRd variables in the General Catalogue of Variable Stars. These stars are shown to be metal-poor supergiants: WY And with [Fe/H]=-1.0, ...
  • 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 ...
  • The Chemical Compositions of the Type II Cepheids-The BL Herculis and W Virginis Variables 
    Maas, T; Giridhar, S; Lambert, D. L (University of Chicago Press, 2007-09)
    Abundance analyses from high-resolution optical spectra are presented for 19 type II Cepheids in the Galactic field. The sample includes both short-period (BL Her) and long-period (W Vir) stars. This is the first extensive ...
  • Comprehensive abundance analysis of red giants in the open clusters NGC 1342, 1662, 1912, 2354 and 2447 
    Reddy, A. B. S; Giridhar, S; Lambert, D. L (Oxford University Press on behalf of the Royal Astronomical Society, 2015-07-11)
    We have observed high-dispersion echelle spectra of red giant members in the five open clusters (OCs) NGC 1342, NGC 1662, NGC 1912, NGC 2354 and NGC 2447 and determined their radial velocities and chemical compositions. ...
  • Comprehensive abundance analysis of red giants in the open clusters NGC 2527, 2682, 2482, 2539, 2335, 2251 and 2266 
    Reddy, A. B. S; Giridhar, S; Lambert, D. L (Oxford University Press on behalf of the Royal Astronomical Society, 2013-06-01)
    We have analysed high-resolution echelle spectra of red giant members for seven open clusters in the Galactic anticentre direction to explore their chemical compositions. Cluster membership has been confirmed by radial ...
  • Comprehensive abundance analysis of red giants in the open clusters NGC 752, 1817, 2360 and 2506 
    Reddy, A. B. S; Giridhar, S; Lambert, D. L (Wiley-Blackwell, 2012-01)
    We have analysed high-dispersion echelle spectra (R ≳ 50 000) of red giant members for four open clusters to derive abundances for many elements. The spread in temperatures and gravities being very small among the red ...
  • Detection of CH+, CH and H2 Molecules in the Young Planetary Nebula IC 4997 
    Kameswara Rao, N; Lambert, D. L; Reddy, A. B. S; Manchado, A; Diaz-Luis, J. J; Garcia-Hernandez, D. A (IOP Publishing, 2020-07-01)
    We have detected CH+ and CH molecular absorption lines from the youngcompact planetary nebula IC 4997 from high resolution optical spectra. A high-resolution infra-red (H and K bands) spectrum provides detection of H2 ...
  • Detection of fluorine in hot extreme helium stars 
    Bhowmick, A; Pandey, G; Lambert, D. L (IOP Publishing, 2020-03-01)
    The main objective of this paper is to explore abundances of fluorine in hot Extreme Helium Stars (EHes). Overabundance of fluorine is a chara cteristic feature for cool EHes and R Coronae Borealis (RCB) stars and ...
  • Dust around R Coronae Borealis Stars. I. Spitzer/Infrared Spectrograph Observations 
    Aníbal García-Hernández, D; Kameswara Rao, N; Lambert, D. L (IOP Publishing, 2011-09-20)
    Spitzer/infrared spectrograph (IRS) spectra from 5 to 37 μm for a complete sample of 31 R Coronae Borealis stars (RCBs) are presented. These spectra are combined with optical and near-infrared photometry of each RCB at ...
  • Dust Around R Coronae Borealis Stars. II. Infrared Emission Features in an H-poor Environment 
    Garcia-Hernandez, D. A; Kameswara Rao, N; Lambert, D. L (IOP Publishing, 2013-08-20)
    Residual Spitzer/Infrared Spectrograph spectra for a sample of 31 R Coronae Borealis (RCB) stars are presented and discussed in terms of narrow emission features superimposed on the quasi-blackbody continuous infrared ...
  • DZ Andromedae : A search for the spectral evidence of its possible RCB nature 
    Goswami, A; Kameswara Rao, N; Lambert, D. L (Astronomical Society of India, 1999)
    The analysis of high-resolution spectra of DZ Andromedae, a suspected R Coronae Borealis variable, is presented here. The spectra of DZ And show the characteristics of a normal K2 III star, indicating that the star was ...
  • Elemental abundance survey of the galactic thick disc 
    Reddy, B. E; Lambert, D. L; Prieto, Carlos Allende (Blackwell Publishing, 2006-04)
    We have performed an abundance analysis for F- and G- dwarfs of the Galactic thick-disc component. A sample of 176 nearby (d≤ 150 pc) thick-disc candidate stars was chosen from the Hipparcos catalogue and subjected to a ...
  • Emission-line spectra of XX Ophiuchi in 1996 and 1997 
    Goswami, A; Kameswara Rao, N; Lambert, D. L (The Observatory, 2001-04)
  • The emission-line spectrum of the hot R Coronae Borealis star MV SGR 
    Pandey, G; Kameswara Rao, N; Lambert, D. L (Royal Astronomical Society, 1996-10)
    Spectra of MV Sgr obtained at CTIO in 1992 May show many emission lines in the red. Most of the emission lines show two components with a minimum centred at the stellar velocity. Species represented include H, HeI, TiII ...
  • Epsilon Aurigae in eclipse. I - Ultraviolet spectroscopy during INGRESS and totality 
    Parthasarathy, M; Lambert, D. L (Astronomical Society of the Pacific, 1983-12)
    Epsilon Aurigae is a long-period eclipsing system containing a F0 Ia supergiant and an unseen slightly less-massive secondary. A primary eclipse began in mid-1982 with the unseen companion passing in front of the supergiant. ...
  • The evolution of the Milky Way: new insights from open clusters 
    Reddy, A. B. S; Lambert, D. L; Giridhar, S (Oxford University Press on behalf of the Royal Astronomical Society, 2016-12)
    We have collected high-dispersion echelle spectra of red giant members in the 12 open clusters (OCs) and derived stellar parameters and chemical abundances for 26 species by either line equivalent widths or synthetic ...
  • 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 ...

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