On the nature of the dwarf carbon star G77-61

Dearborn, D. S. P.; Liebert, James; Aaronson, M.; Dahn, C. C.; Harrington, R. S.; Mould, Jeremy; Greenstein, Jesse L.

doi:10.1086/163805

Cited by 70 publications

(79 citation statements)

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“…The first such case was G77-61 with a classical carbon star spectrum but a high proper motion suggesting a main sequence luminosity. It is a spectroscopic binary and mass transfer is a likely explanation for it (Dearborn et al, 1986). Additional examples have now been found Green et al, 1992;Warren et al, 1993).…”

Section: Barium and Related Starsmentioning

confidence: 85%

Synthesis of the elements in stars: forty years of progress

et al. 1997

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Forty years ago Burbidge, Burbidge, Fowler, and Hoyle combined what we would now call fragmentary evidence from nuclear physics, stellar evolution and the abundances of elements and isotopes in the solar system as well as a few stars into a synthesis of remarkable ingenuity. Their review provided a foundation for forty years of research in all of the aspects of low energy nuclear experiments and theory, stellar modeling over a wide range of mass and composition, and abundance studies of many hundreds of stars, many of which have shown distinct evidence of the processes suggested by B 2 FH. In this review we summarize progress in each of these fields with emphasis on the most recent developments. [S0034-6861(97)

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Section: Barium and Related Starsmentioning

confidence: 85%

Synthesis of the elements in stars: forty years of progress

et al. 1997

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“…The orbital similarity between these two groups is a further indication that their different names stem from historical reasons, but there is no physical difference between them, apart from the fact that CH systems always involve giant primaries, whereas CEMP systems comprise dwarf primaries as well (see the d/g column in Table 4). Long-standing historical equivalents of the dwarf CEMP-s stars are the subgiant CH stars (Luck & Bond 1991) and the formerly known dwarf carbon stars, such as G77-61 (Dearborn et al 1986; see Table 9.5 of Jorissen 2004 for a review) or the "carbon dwarf wearing a necklace", the central star of the planetary nebula G054.2 -03.4 (Corradi et al 2011;Miszalski et al 2013). The latter has not been listed explicitly in Table 4 because it is not formally known as a CH or CEMP star.…”

Section: Cemp-s Vs Ch Systemsmentioning

confidence: 99%

Binary properties of CH and carbon-enhanced metal-poor stars

Jorissen

Eck

Winckel

et al. 2016

A&A

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The HERMES spectrograph installed on the 1.2-m Mercator telescope has been used to monitor the radial velocity of 13 lowmetallicity carbon stars, among which seven carbon-enhanced metal-poor (CEMP) stars and six CH stars (including HIP 53522, a new member of the family, as revealed by a detailed abundance study). All stars but one show clear evidence for binarity. New orbits are obtained for eight systems. The sample covers an extended range in orbital periods, extending from 3.4 d (for the dwarf carbon star HE 0024-2523) to about 54 yr (for the CH star HD 26, the longest known among barium, CH, and extrinsic S stars). Three systems exhibit low-amplitude velocity variations with periods close to 1 yr superimposed on a long-term trend. In the absence of an accurate photometric monitoring of these systems, it is not clear yet whether these variations are the signature of a very lowmass companion or of regular envelope pulsations. The period -eccentricity (P − e) diagram for the 40 low-metallicity carbon stars with orbits now available shows no difference between CH and CEMP-s stars (the latter corresponding to those CEMP stars enriched in s-process elements, as are CH stars). We suggest that they must be considered as one and the same family and that their different names only stem from historical reasons. Indeed, these two families have as well very similar mass-function distributions, corresponding to companions with masses in the range 0.5-0.7 M , indicative of white-dwarf companions, adopting 0.8-0.9 M for the primary component. This result confirms that CH and CEMP-s stars obey the same mass-transfer scenario as their highermetallicity analogues, barium stars. The P − e diagrams of barium, CH, and CEMP-s stars are indeed very similar. They reveal two different groups of systems: one with short orbital periods (P < 1000 d) and mostly circular or almost circular orbits, and another with longer period and eccentric (e > 0.1) orbits. These two groups either trace different evolutionary channels during the mass-transfer episode responsible for the chemical peculiarities of the Ba/CH/CEMP-s stars, or result from the operation of tidal circularisation in a more recent past, when the current giant star was ascending the first giant branch.

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“…The other dwarf, G77-61, with the second shortest period, deserves comment because of the rather weak carbon enrichment of ½C/ H $ À1:4 (Plez & Cohen 2005). It has the mass $0.3 M (Dearborn et al 1986) and is likely to be wholly convective. In addition, the cross section of the star for the accretion is a factor of $7 smaller than that of a red giant CEMP star (see eq.…”

Section: Periodycarbon Enhancement Relationmentioning

confidence: 99%

The Origin of Carbon Enhancement and the Initial Mass Function of Extremely Metal‐poor Stars in the Galactic Halo

Komiya

Suda

Minaguchi

et al. 2007

ApJ

130

220

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It is known that the carbon-enhanced, extremely metal-poor (CEMP) stars constitute a substantial proportion of the extremely metal-poor (EMP) stars of the Galactic halo, and a by far larger proportion than CH stars among Population II stars. We investigate their origin by taking into account an additional evolutionary path to the surface carbon enrichment, triggered by hydrogen engulfment by the helium flash convection, in EMP stars with ½Fe/H P À2:5. This process is distinct from the third dredge-up operating in more metal-rich stars and in EMP stars. In binary systems of EMP stars, the secondary stars become CEMP stars through mass transfer from the low-and intermediatemass primary stars that have developed the surface carbon enhancement. Our binary scenario can predict the variations in the abundances not only for carbon but also for nitrogen and s-process elements and can reasonably explain the observed properties such as the stellar distributions of the carbon abundances, the binary periods, and the evolutionary stages. Furthermore, from the observed frequencies of CEMP stars with and without s-process element enhancement, we demonstrate that the initial mass function of EMP stars needed gives the mean mass $ 10 M under the reasonable assumptions for the distributions of orbital separations and mass ratios of the binary components. This also indicates that the currently observed EMP stars were exclusively born as the secondary members of binaries, making up $10% of EMP binary systems, with mass $ 10 8 M in total; in addition to CEMP stars with white dwarf companions, a significant fraction of them have experienced supernova explosions of their companions. We discuss the implications of the present results for the formation of the Galactic halo.

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On the nature of the dwarf carbon star G77-61

Cited by 70 publications

References 0 publications

Synthesis of the elements in stars: forty years of progress

Synthesis of the elements in stars: forty years of progress

Binary properties of CH and carbon-enhanced metal-poor stars

The Origin of Carbon Enhancement and the Initial Mass Function of Extremely Metal‐poor Stars in the Galactic Halo

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