Topic
Lead star
About: Lead star is a research topic. Over the lifetime, 7 publications have been published within this topic receiving 181 citations.
Papers
TL;DR: In this paper, a high-resolution spectroscopic study of a sample of 23 carbon-enhanced, metal-poor (CEMP) stars was performed in order to gain a better understanding of s-and r-process nucleosynthesis at low metallicity, and to investigate the role of duplicity.
Abstract: Context. The remarkable properties of CS 30322-023 became apparent during the course of a high-resolution spectroscopic study of a sample of 23 carbon-enhanced, metal-poor (CEMP) stars. Aims. This sample is studied in order to gain a better understanding of s- and r-process nucleosynthesis at low metallicity, an d to investigate the role of duplicity. Methods. High-resolution UVES spectra have been obtained, and abundances are derived using 1-D, plane-parallel OSMARCS models under the LTE hypothesis. The derived atmospheric parameters and observed abundances are compared to evolutionary tracks and nucleosynthesis predictions to infer the evolutionary status of CS 30322-023. Results. CS 30322-023 is remarkable in having the lowest surface gravity (log g≤ −0.3) among the metal-poor stars studied to date. As a result of its rather low temperature (4100 K), abundances could be derived for 35 chemical elements; the abundance pattern of CS 30322-023 is one of the most well-specified of all known extremely metal -poor stars. With [Fe/H]=−3.5, CS 30322-023 is the most metal-poor star to exhibit a clear s-process signature, and the most metal-poor “lead star” known. The available evidence indicates that CS 30322-023 is presently a thermally-pulsing asymptotic giant branch (TP-AGB) star, with no strong indication of binarity thus far (although a s ignal of period 192 d is clearly present in the radial-velocity data, this is like ly due to pulsation of the stellar envelope). Low-mass TP-AGB stars are not expected to be exceedingly rare in a magnitude-limited sample such as the HK survey, because their high luminosities make it possible to sample them over a very large volume. The strong N overabundance and the low 12 C/ 13 C ratio (4) in this star is typical of the operation of the CN cycle. Coupled with a Na overabundance and the absence of a strong C overabundance, this pattern seems to imply that hot-bottom burning operated in this star, which should then have a mass of at least 2 M⊙. However, the luminosity associated with this mass would put the star at a distance of about 50 kpc, in the outskirts of the galactic ha lo, where no recent star formation is expected to have taken place. We explore alternative scenarios in which the observed abundance pattern results from some mixing mechanism yet to be identified oc curring in a single low-metallicity 0.8 M⊙ AGB star, or from pollution by matter from an intermediate-mass AGB companion which has undergone hot-bottom burning. We stress, however, that our abundances may be subject to uncertainties due to NLTE or 3D granulation effects which were not taken into consideration.
111 citations
TL;DR: In this article, a detailed spectroscopic and kinematic study of CD-62 ◦ 1346 was carried out and the distance and the evolutionary state of the star were significantly refined.
Abstract: Context. High-velocity halo stars provide important information about the properties of the extreme Galactic halo. The study of unbound and bound Population II stars permits us to better estimate the mass of the halo. Aims. We carried out a detailed spectroscopic and kinematic study and have significantly refined the distance and the evolutionary state of the star. Methods. Its atmospheric parameters, chemical abundances and kinematical properties were determined using high-resolution optical spectroscopy and employing the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code moog. Results. We found that CD-62 ◦ 1346 is a metal-poor ([Fe/H] = −1.6) evolved giant star with Teff = 5300 K and log g = 1.7. The star exhibits high carbon and s-element abundances typical of CH stars. It is also a lead star. Our kinematic analysis of its 3D space motions shows that this star has a highly eccentric (e = 0.91) retrograde orbit with an apogalactic distance of ∼100 kpc, exceeding by a factor of two the distance of the Magellanic Clouds. The star travels with very high velocity relative to the Galactocentric reference frame (VGRF = 570 km s −1 ). Conclusions. CD-62 ◦ 1346 is an evolved giant star and not a subgiant star, as was considered earlier. Whether it is bound or unbound to the Galaxy depends on the assumed mass and on the adopted Galactic potential. We also show that the star HD 5223 is another example of a high-velocity CH star that exceeds the Galactic escape velocity. Possible origins of these two high-velocity stars are briefly discussed. CD-62 ◦ 1346 and HD 5223 are the first red giant stars to join the restricted group of hypervelocity stars.
37 citations
TL;DR: In this article, a detailed spectroscopic and kinematic study of CD-62$\degr$1346 was carried out and the distance and the evolutionary state of the star were significantly refined.
Abstract: High-velocity halo stars provide important information about the properties of the extreme Galactic halo. The study of unbound and bound Population II stars permits us to better estimate the mass of the halo.} {We carried out a detailed spectroscopic and kinematic study and have significantly refined the distance and the evolutionary state of the star. Its atmospheric parameters, chemical abundances and kinematical properties were determined using high-resolution optical spectroscopy and employing the local-thermodynamic-equilibrium model atmospheres of Kurucz and the spectral analysis code {\sc moog}. We found that CD-62$\degr$1346 is a metal-poor ([Fe/H]=$-$1.7) evolved giant star with $T_{\rm eff}=5300$ K and $\log g=1.7$. The star exhibits high carbon and s-element abundances typical of CH stars. It is also a lead star. Our kinematic analysis of its 3D space motions shows that this star has a highly eccentric ($e=0.91$) retrograde orbit with an apogalactic distance of $\sim 100$ kpc, exceeding by a factor of three the distance to the Magellanic Clouds. The star travels with very high velocity relative to the Galactocentric reference frame ($V_{\rm GRF}=570$ km\,s$^{-1}$). CD-62$\degr$1346 is an evolved giant star and not a subgiant star, as was considered earlier. Whether it is bound or unbound to the Galaxy depends on the assumed mass and on the adopted Galactic potential. We also show that the star HD 5223 is another example of a high-velocity CH star that exceeds the Galactic escape velocity. Possible origins of these two high-velocity stars are briefly discussed. CD-62$\degr$1346 and HD 5223 are the first red giant stars to join the restricted group of hypervelocity stars.
32 citations
1 Jan 2011
TL;DR: In this paper, the atmospheric parameters and abundance pattern of the chemically peculiar metal-poor Fehrenbach & Duflot (Feh-Duf) star were determined using high resolution optical spectroscopy and employing the local-thermodynamic-equilibrium model atmospheres of Kurucz and spectral analysis code MOOG.
Abstract: Aims. We determine the atmospheric parameters and abundance pattern of the chemically peculiar metal-poor Fehrenbach & Duflot (Feh-Duf) star to more clearly understand its evolutionary state and the nature of the s-element enhancement in this star. Methods. Its atmospheric parameters and chemical abundances were determined using high resolution optical spectroscopy and employing the local-thermodynamic-equilibrium model atmospheres of Kurucz and spectral analysis code MOOG. Results. The derived abundances show that the Feh-Duf star is a low-metallicity ([Fe/H] = −1.93) star with high carbon and heavy s-element abundances, while the abundance of the light s-process element yttrium is low ([Y/Fe] = −0.07). The oxygen abundance is lower than for Galactic halo stars of similar metallicity.We conclude that the Feh-Duf star could be a CH star with C/O = 1.3. Another possibility is that the Feh-Duf star could be an early-AGB star. The Fehrenbach & Duflot star is also a lead star with [Pb/Ce] =+ 0.69. In addition, it displays an extreme retrograde motion (VGRF = −259 km s −1 ), which in combination with its underabundance of α-elements suggests that this star may have been captured by the Milky Way galaxy.
TL;DR: In this article, the atmospheric parameters and chemical abundances of the Fehrenbach & Duflot (Feh-Duf) star were determined using high resolution optical spectroscopy and employing the local-thermodynamic-equilibrium model atmospheres of Kurucz and spectral analysis code MOOG.
Abstract: Aims. We determine the atmospheric parameters and abundance pattern of the chemically peculiar metal-poor Fehrenbach & Duflot (Feh-Duf) star to more clearly understand its evolutionary state and the nature of the s-element enhancement in this star.Methods. Its atmospheric parameters and chemical abundances were determined using high resolution optical spectroscopy and employing the local-thermodynamic-equilibrium model atmospheres of Kurucz and spectral analysis code MOOG.Results. The derived abundances show that the Feh-Duf star is a low-metallicity ([Fe/H] = −1.93) star with high carbon and heavy s-element abundances, while the abundance of the light s-process element yttrium is low ([Y/Fe] = −0.07). The oxygen abundance is lower than for Galactic halo stars of similar metallicity.We conclude that the Feh-Duf star could be a CH star with C/O = 1.3. Another possibility is that the Feh-Duf star could be an early-AGB star. The Fehrenbach & Duflot star is also a lead star with [Pb/Ce] = +0.69. In addition, it displays an extreme retrograde motion (V GRF = −259 km s-1 ), which in combination with its underabundance of α -elements suggests that this star may have been captured by the Milky Way galaxy.
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| Year | Papers |
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| 2017 | 1 |
| 2014 | 1 |
| 2012 | 2 |
| 2011 | 2 |
| 2006 | 1 |