Journal article
The abundances of carbon and nitrogen in the atmospheres of classical Be stars
Astrophysics and space science, Vol.371(1), 9
2026
DOI: 10.1007/s10509-026-04538-8
PMID: 41608613
Abstract
Hot stars born as rapid rotators are expected to induce meridional currents that mix hydrogen from the envelope into the core and return CNO-cycle processed material to the envelope, which should enhance the N at the surface at the expense of C and possibly also O depending on the ambient conditions. But the photospheric C and N abundances could also be influenced by mass transfer in a close binary system which spins up the mass gainer and deposits either processed or unprocessed material to its surface depending on just how much material has been peeled off the mass donor. We focus on the chemical composition of Be star photospheres to infer the present and past evolution of rapidly rotating early B stars. To mitigate the effects of gravity darkening and photospheric line blending on the abundances, we chose 8 Be stars with low
that have good high-resolution FUV spectra in the
archive. We carried out a conventional NLTE abundance analysis of selected N iii, N i, and C iii lines in the FUV spectral region. We find clear evidence that the C iii 1176 Å multiplet is weak in the core region in most program stars, suggesting CNO processing. However, in all cases we infer a N abundance that is solar or less, raising a conundrum as to what happened to the "missing C." Since a similar pattern of weak C yet normal N is also found in the mass gainer in some Algol binaries, there appears to be an emerging challenge to explain this apparent abundance anomaly. We speculate that the excess N from CNO processing might be converted into O (and perhaps on to Ne) by fusion with He in the hot but low-density regions either in the trail of ashes just outside the receding carbon-fusing core, or in He-shell flash regions, of a highly evolved mass loser in its final stage of mass transfer.
Details
- Title: Subtitle
- The abundances of carbon and nitrogen in the atmospheres of classical Be stars
- Creators
- Geraldine J Peters - University of Southern CaliforniaKenneth G Gayley - University of IowaRina G Rast - Western UniversityJorick S Vink - Armagh Observatory & PlanetariumJeremy J Drake - Lockheed Martin
- Resource Type
- Journal article
- Publication Details
- Astrophysics and space science, Vol.371(1), 9
- DOI
- 10.1007/s10509-026-04538-8
- PMID
- 41608613
- ISSN
- 0004-640X
- eISSN
- 1572-946X
- Publisher
- Springer
- Grant note
- Natural Sciences and Engineering Research Council of CanadaHubble Space Telescope: HST-GO-17445.002-A, HST-GO-17095.003-A, HST-GO-15659.002-A, and HST-GO-GO15869.00 University of Southern California
Open access funding provided by SCELC, Statewide California Electronic Library Consortium
- Language
- English
- Date published
- 2026
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9985132204502771
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