CO bands in V4334 Sgr (Sakurai's Object): The $\mathsf{^{12}}$C/$\mathsf{^{13}}$C ratio

Pavlenko, Ya. V.; Geballe, T. R.; Evans, A.; Smalley, B.; Eyres, S. P. S.; Tyne, V. H.; Yakovina, L. A.

doi:10.1051/0004-6361:20040078

Cited by 40 publications

(57 citation statements)

References 15 publications

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“…The equilibrium isotopic ratio of carbon in CNO burning is 3.5. In Sakurai's object, the 12 C/ 13 C ratio is about 4 (Asplund et al 1997b;Pavlenko et al 2004), consistent with hot proton-limited-burning predictions in the context of the very late thermal pulse that causes a born-again evolution. Moreover, Sakurai's object has shown no indication of enhanced 18 O (Eyres et al 1998).…”

Section: Observations and Resultssupporting

confidence: 77%

An Extremely Large Excess of ¹⁸ O in the Hydrogen-deficient Carbon Star HD 137613

Clayton¹,

Herwig²,

Geballe³

et al. 2005

ApJ

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We report the discovery of a uniquely large excess of 18 O in the hydrogen-deficient carbon (HdC) star HD 137613 based on a spectrum of the first-overtone bands of CO at 2.3-2.4 mm in which three strong absorption bands of 12 O Շ 1. The solar value of this ratio is ∼500. Neither He-core burning nor He-shell flash burning can produce the isotopic ratios of oxygen and carbon observed in HD 137613. However, a remarkable similarity exists between the observed abundances and those found in the outer layers of the broad He shell of early-asymptotic giant branch (AGB) stars, soon after the end of He-core burning. It is not known how the outer envelope down to the He shell could be lost, but some mechanism of enhanced mass loss must be involved. HD 137613 may be a post-early-AGB star with the outer layers of the former He-burning shell as its photosphere. The unusual elemental abundances of the HdC stars resemble those of the R Coronae Borealis (RCB) stars, but HdC stars do not produce clouds of dust that produce declines in brightness. None of the other RCB or HdC stars observed show significant 18 O.

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Section: Observations and Resultssupporting

confidence: 77%

An Extremely Large Excess of ¹⁸ O in the Hydrogen-deficient Carbon Star HD 137613

Clayton¹,

Herwig²,

Geballe³

et al. 2005

ApJ

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“…As expected, a low value of 12 C/ 13 C ratio is shown by the FF object V4334 Sgr (Sakurai's object), the ratio is 2-5 (Asplund et al 1997b;Pavlenko et al 2004). However, the other objects which are thought to be FF objects, such as FG Sge (Gonzalez et al 1998) and V605 Aql (Lundmark 1921;Clayton & De Marco 1997), do not show the presence of 12 C 13 C bands in their spectrum.…”

Section: Introductionsupporting

confidence: 54%

The Galactic R Coronae Borealis Stars: The C2 Swan Bands, The Carbon Problem, and The 12C/13C Ratio

Hema¹,

Pandey²,

Lambert³

2013

Proceedings of XII International Symposium on Nuclei in the Cosmos — PoS(NIC XII)

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Observed spectra of R Coronae Borealis (RCB) and hydrogen-deficient carbon (HdC) stars are analyzed by synthesizing the C 2 Swan bands (1, 0), (0, 0), and (0, 1) using our detailed line list and the Uppsala model atmospheres. The (0, 1) and (0, 0) C 2 bands are used to derive the 12 C abundance, and the (1, 0) 12 C 13 C band to determine the 12 C/ 13 C ratios. The carbon abundance derived from the C 2 Swan bands is about the same for the adopted models constructed with different carbon abundances over the range 8.5 (C/He = 0.1%) to 10.5 (C/He = 10%). Carbon abundances derived from C i lines are about a factor of four lower than the carbon abundance of the adopted model atmosphere over the same C/He interval, as reported by Asplund et al., who dubbed the mismatch between adopted and derived C abundance as the "carbon problem." In principle, the carbon abundances obtained from C 2 Swan bands and that assumed for the model atmosphere can be equated for a particular choice of C/He that varies from star to star. Then, the carbon problem for C 2 bands is eliminated. However, such C/He ratios are in general less than those of the extreme helium stars, the seemingly natural relatives to the RCB and HdC stars. A more likely solution to the C 2 carbon problem may lie in a modification of the model atmosphere's temperature structure. The derived carbon abundances and the 12 C/ 13 C ratios are discussed in light of the double degenerate and the final flash scenarios.

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“…The number of stars with secular changes in a human lifetime (even our very extended one) remains small, and nothing like FG Sge (Arkhipova et al 2003) or V4334 Sgr (Pavlenko et al 2004) appeared this year. But the youngest known runaway star (the Becklin-Neugebauer object) may have begun its selfenshrouding mass loss as a result of a close encounter only 500 years ago (Tan 2004).…”

Section: Inventoriesmentioning

confidence: 88%

“…convection provides, in B stars (Hempel & Holweger 2003) and red giants in globular clusters (Pavlenko et al 2003), an equally random pair near the beginning of the annual ensemble. Sometimes, however, the mixing is just right ( Now you compare your tracks with data on binary stars, clusters, and so forth and pronounce judgement.…”

Section: Tracks In the Hr Diagrammentioning

confidence: 99%

Astrophysics in 2004

Trimble

Aschwanden

2005

PUBL ASTRON SOC PAC

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CO bands in V4334 Sgr (Sakurai's Object): The $\mathsf{^{12}}$C/$\mathsf{^{13}}$C ratio

Cited by 40 publications

References 15 publications

An Extremely Large Excess of ¹⁸ O in the Hydrogen-deficient Carbon Star HD 137613

An Extremely Large Excess of ¹⁸ O in the Hydrogen-deficient Carbon Star HD 137613

The Galactic R Coronae Borealis Stars: The C2 Swan Bands, The Carbon Problem, and The 12C/13C Ratio

Astrophysics in 2004

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CO bands in V4334 Sgr (Sakurai's Object): The $\mathsf{^{12}}$C/$\mathsf{^{13}}$C ratio

Cited by 40 publications

References 15 publications

An Extremely Large Excess of 18 O in the Hydrogen-deficient Carbon Star HD 137613

An Extremely Large Excess of 18 O in the Hydrogen-deficient Carbon Star HD 137613

The Galactic R Coronae Borealis Stars: The C2 Swan Bands, The Carbon Problem, and The 12C/13C Ratio

Astrophysics in 2004

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An Extremely Large Excess of ¹⁸ O in the Hydrogen-deficient Carbon Star HD 137613

An Extremely Large Excess of ¹⁸ O in the Hydrogen-deficient Carbon Star HD 137613