Related papers: Low Mass Stars and the He3 Problem
We follow the evolution of 3He in stars of mass 0.8 -- 10 M (solar units) for Pop. I and II compositions from the main sequence until advanced stages on the AGB. Under standard assumptions we confirm earlier results of more restricted…
Inhomogeneous chemical evolution models of galaxies which try to reproduce the scatter seen in element-to-iron ratios of metal-poor halo stars are heavily dependent on theoretical nucleosynthesis yields of core-collapse supernovae. Hence…
Numerical models for the chemical evolution of the Galaxy have been computed with the new stellar yields published by Maeder (1992). These metallicity dependent yields represent an important improvement in the chemical evolution of galaxies…
Intermediate mass stars occupy the mass range between 0.8-8 solar masses. In this review, evolutionary models of these stars from numerous sources are compared in terms of their input physics and predicted yields. In particular, the results…
Context. Growing evidence is revealing the crucial role of binarity in massive star evolution. This affects evolution models and demands a refinement of the available observational constraints. Aims. To investigate the possible evolutionary…
The primary goal of this paper is to make a direct comparison between the measured and model-predicted abundances of He, C and N in a sample of 35 well-observed Galactic planetary nebulae (PN). All observations, data reductions, and…
Stellar nucleosynthesis is the corner-stone of many astrophysical problems. Its understanding, which can be tested by countless observations, leads to insights into the stellar structure and evolution, and provides crucial clues to the…
A project which aims to understand the abundance patterns of He, C, N, O, Ne, S, and Ar for a small sample of planetary nebulae is described. Abundance ratios of O/H, C/O, and N/O especially show a broad range relative to their solar…
Population III (Pop III) stars ended the cosmic Dark Ages and began early cosmological reionization and chemical enrichment. However, in spite of their importance to the evolution of the early Universe, their properties remain uncertain…
A long sought after goal using chemical abundance patterns derived from metal-poor stars is to understand the Galactic chemical evolution (GCE) and to pin down the nature of the first stars (Pop III). Here, we use a sample of 14 metal-poor…
Current numerical studies suggest that the first galaxies formed a few stars at a time and were enriched only gradually by the first heavy elements. However, the large box sizes in these models cannot resolve primordial supernova explosions…
The first stars likely formed from pristine clouds, marking a transformative epoch after the dark ages by initiating reionisation and synthesising the first heavy elements. Among these, low-mass Population III stars are of particular…
We review the yields of intermediate mass elements (from C to Zn) from massive stars and their associated uncertainties, in the light of recent theoretical results. We consider the role of those yields for our understanding of the chemical…
The chemical enrichment of the Universe; the mass spectrum of planetary nebulae, white dwarfs and gravitational wave progenitors; the frequency distribution of Type I and II supernovae; the fate of exoplanets ... a multitude of phenomena…
We present preliminary results of stellar structure and nucleosynthesis calculations for some early stars. The study (still in progress) seeks to explore the expected chemical signatures of second generation low- and intermediate-mass stars…
Observations of stellar CNO isotope ratios indicate the presence of additional mixing processes on the red giant branch. An estimate of the resulting stellar He-3 depletion is made, as a function of stellar mass and metallicity. Based on…
In Pop III stellar models convection-induced mixing between H- and He-rich burning layers can induce a burst of nuclear energy and thereby substantially alter the subsequent evolution and nucleosynthesis in the first massive stars. We…
We examine the impact of discrete numbers of stars in stellar populations on the results of Chemical Evolution Models. We explore the resulting dispersion in the true yields and their possible relation with the dispersion in observational…
One-zone Galactic Chemical Evolution (GCE) models have provided useful insights on a great wealth of average abundance patterns in many environments, especially for the Milky Way and its satellites. However, the scatter of such abundance…
The observations of carbon isotopic ratios in evolved stars suggest that non standard mixing is acting in low mass stars as they are ascending the red giant branch. We propose a simple consistent mechanism, based on the most recent…