Fluorine in R Coronae Borealis Stars

Abstract

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 is enriched in some RCBs by factors of 800 to 8000 relative to its likely initial abundance. The overabundances of fluorine are evidence for the synthesis of fluorine. These results are discussed in the light of the scenario that RCBs are formed by accretion of an He white dwarf by a C-O white dwarf. Sakurai's object (V4334 Sgr), a final He-shell flash product, shows no detectable F I lines.

25 pages, 7 figures, accepted to ApJ

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• The ongoing pursuit of R Coronae Borealis stars: ASAS-3 survey strikes again
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• A proposed direct measurement of cross section at Gamow window for key reaction ${}^{19}$F($p$,$\alpha$)${}^{16}$O in Asymptotic Giant Branch stars with a planned accelerator in CJPL
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• New R Coronae Borealis stars discovered in OGLE-III Galactic Bulge fields from their mid- and near- infrared properties
• Fluorine Abundances in the Galactic Nuclear Star Cluster
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• The Double Dust Envelopes of R Coronae Borealis Stars
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• Abundance analyses of the new R Coronae Borealis stars: ASAS-RCB-8 and ASAS-RCB-10
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• Revised surface abundances of R Coronae Borealis stars
• On the cosmic origin of Fluorine
• Exploring fluorine chemical evolution in the Galactic disk: the open cluster perspective
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• Merged white dwarfs and nucleosynthesis