Can the Core Helium Flash Synthesize Lithium and Dredge it Up?

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dc.catalogadorgrr
dc.contributor.advisorChanamé, Julio
dc.contributor.authorVilaza Dallago, Sebastian Javier
dc.contributor.otherPontificia Universidad Católica de Chile. Instituto de Astrofísica
dc.date.accessioned2025-11-05T16:17:47Z
dc.date.available2025-11-05T16:17:47Z
dc.date.issued2025
dc.date.updated2025-10-22T09:53:55Z
dc.descriptionTesis (Master’s degree in Astrophysics)--Pontificia Universidad Católica de Chile, 2025
dc.description.abstractThe existence of lithium-rich (Li-rich) red giant stars challenges standard stellar evolution models. Although several mechanisms have been proposed, the origin of Li enrichment remains a mystery. Recent asteroseismic and spectroscopic evidence suggests that most Li-rich giants are low-mass red clump (RC) stars that have undergone the core helium (He) flash, indicating a possible connection with this event. Motivated by multi-dimensional hydrodynamical simulations, in this work I investigate whether the core He-flash in low-mass stars can trigger a proton ingestion episode (PIE) that produces lithium. Using the MESA stellar evolution code I compare standard evolution with models where a PIE is induced by implementing enhanced overshooting, in a 1.2 Msun star with subsolar metallicity ([Fe/H] = -0.3). These models show that PIEs can occur at near-solar metallicity, producing a secondary hydrogen flash followed by a dredge-up event. Although lithium and beryllium are synthesized during the PIE, which if they were dredged up they could enhance the surface Li-abundance up to a value of A(Li)~4.8, being able to explain even the most Li-rich giants, both Li and Be are destroyed before the dredge-up event, resulting in no surface enrichment. In the PIE-induced models, the post-PIE evolution diverges from standard models, with a second RGB ascent and secondary He-flash occurring before stable core He-burning. The PIE also produces substantial s-process elements via the 13C(alpha, n)16O reaction, which are dredged up to the surface, enhancing their abundance by 2–3 dex. The non-standard evolution and strong s-process enhancement contradict current observations of Li-rich red clump giants. While PIEs remain a theoretically promising mechanism for internal Li enrichment, current results do not support them as the origin of Li-rich giants. However, open questions remain before the scenario can be definitively ruled out.
dc.fechaingreso.objetodigital2025-10-22
dc.format.extent90 páginas
dc.fuente.origenAutoarchivo
dc.identifier.doi10.7764/tesisUC/AST/106526
dc.identifier.urihttps://doi.org/10.7764/tesisUC/AST/106526
dc.identifier.urihttps://repositorio.uc.cl/handle/11534/106526
dc.information.autorucInstituto de Astrofísica; Vilaza Dallago, Sebastian Javier; S/I; 1064499
dc.information.autorucInstituto de Astrofísica; Chanamé, Julio ; 0000-0003-2481-4546; 104380
dc.language.isoen
dc.nota.accesocontenido completo
dc.rightsacceso abierto
dc.rights.licenseAtribución-NoComercial-SinDerivadas 4.0 Internacional (CC BY-NC-ND 4.0)
dc.rights.urihttps://creativecommons.org/licenses/by-nc-nd/4.0/deed.es
dc.subject.ddc520
dc.subject.deweyAstronomíaes_ES
dc.tipo.dtdEstudio o análisis teórico
dc.titleCan the Core Helium Flash Synthesize Lithium and Dredge it Up?
dc.typetesis de maestría
sipa.codpersvinculados1064499
sipa.codpersvinculados104380
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