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Nature versus nurture: distinguishing effects from stellar processing and chemical evolution on carbon and nitrogen in red giant stars

The surface [C/N] ratios of evolved giants are strongly affected by the first dredge-up (FDU) of nuclear-processed material from stellar cores. C and N also have distinct nucleosynthetic origins and serve as diagnostics of mixing and mass-loss. We use subgiants to find strong trends in the birth [C/...

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Main Authors: Roberts, John (Author) , Pinsonneault, Marc H (Author) , Johnson, Jennifer A (Author) , Zinn, Joel C (Author) , Weinberg, David H (Author) , Vrard, Mathieu (Author) , Tayar, Jamie (Author) , Stello, Dennis (Author) , Mosser, Benoît (Author) , Johnson, James W (Author) , Cao, Kaili (Author) , Stassun, Keivan G (Author) , Stringfellow, Guy S (Author) , Serenelli, Aldo (Author) , Mathur, Savita (Author) , Hekker, Saskia (Author) , García, Rafael A (Author) , Elsworth, Yvonne P (Author) , Corsaro, Enrico (Author)
Format: Article (Journal)
Language:English
Published: May 2024
In: Monthly notices of the Royal Astronomical Society
Year: 2024, Volume: 530, Issue: 1, Pages: 149-166
ISSN:1365-2966
DOI:10.1093/mnras/stae820
Online Access:Verlag, kostenfrei, Volltext: https://doi.org/10.1093/mnras/stae820
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Author Notes:John D Roberts, Marc H Pinsonneault, Jennifer A Johnson, Joel C Zinn, David H Weinberg, Mathieu Vrard, Jamie Tayar, Dennis Stello, Benoît Mosser, James W Johnson, Kaili Cao, Keivan G Stassun, Guy S Stringfellow, Aldo Serenelli, Savita Mathur, Saskia Hekker, Rafael A García, Yvonne P Elsworth and Enrico Corsaro
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Summary:The surface [C/N] ratios of evolved giants are strongly affected by the first dredge-up (FDU) of nuclear-processed material from stellar cores. C and N also have distinct nucleosynthetic origins and serve as diagnostics of mixing and mass-loss. We use subgiants to find strong trends in the birth [C/N] with [Fe/H], which differ between the low-α and high-α populations. We demonstrate that these birth trends have a strong impact on the surface abundances after the FDU. This effect is neglected in current stellar models, which use solar-scaled C and N. We map out the FDU as a function of evolutionary state, mass, and composition using a large and precisely measured asteroseismic data set in first-ascent red giant branch (RGB) and core He-burning, or red clump (RC), stars. We describe the domains where [C/N] is a useful mass diagnostic and find that the RC complements the RGB and extends the range of validity to higher mass. We find evidence for extra mixing on the RGB below [Fe/H] = −0.4, matching literature results, for high-α giants, but there is no clear evidence of mixing in the low-α giants. The predicted signal of mass-loss is weak and difficult to detect in our sample. We discuss implications for stellar physics and stellar population applications.
Item Description:Gesehen am 06.11.2024
Physical Description:Online Resource
ISSN:1365-2966
DOI:10.1093/mnras/stae820

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