相关论文: 3He in stars of low and intermediate mass
Recent observations of 3He/H in different environments tend to prove that 3He is not produced in low mass stars, contrary to the standard predictions of stellar evolution theory. We show how a simple consistent mechanism, namely…
Three-dimensional stellar modeling has enabled us to identify a deep-mixing mechanism that must operate in all low mass giants. This mixing process is not optional, and is driven by a molecular weight inversion created by the 3He(3He,2p)4He…
Standard stellar evolution models that only consider convection as a physical process to mix material inside of stars predict the production of significant amounts of 3He in low-mass stars (M < 2 Msun), with peak abundances of 3He/H ~ few x…
We examine the stability and observational consequences of mixing induced by 3He burning in the envelopes of first ascent red giants. We demonstrate that there are two unstable modes: a rapid, nearly adiabatic mode that we cannot identify…
Low-mass stars, ~1-2 solar masses, near the Main Sequence are efficient at producing 3He, which they mix into the convective envelope on the giant branch and distribute into the Galaxy by way of envelope loss. This process is so efficient…
Low-mass stars, ~1-2 solar masses, near the Main Sequence are efficient at producing He-3, which they mix into the convective envelope on the giant branch and should distribute into the Galaxy by way of envelope loss. This process is so…
To understand the chemical evolution of the Galaxy, we need to understand the contribution of PNe in the 3He abundance. 3He abundances have been detected only in a couple of PNe, their abundances are consistent with the standard models, in…
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…
Context. The 3He content of Galactic HII regions is very close to that of the Sun and the solar system, and only slightly higher than the primordial 3He abundance as predicted by the standard Big Bang nucleosynthesis. However, the classical…
Numerous spectroscopic observations provide compelling evidence for a non-canonical mixing process that modifies the surface abundances of Li, C and N of low-mass red giants when they reach the bump in the luminosity function. Eggleton et…
We investigate the impact of an early population of massive stars on their surroundings. Dissociation of molecular hydrogen by strong UV emission from such stars is expected to produce a global transition in the cooling mechanism of…
We recall the current status of the long-standing 3He problem, and its possible connection with chemical anomalies on the red giant branch. In this context, we collect in the literature all the available observations of the carbon isotopic…
Thermohaline mixing has recently been proposed to occur in low-mass red giants, with large consequence for the chemical yields of low-mass stars. We investigate the role of thermohaline mixing during the evolution of stars between 1Msun and…
Thermohaline mixing has recently been proposed to occur in low mass red giants, with large consequences for the chemical yields of low mass stars. We investigate the role of thermohaline mixing during the evolution of stars between 1Msun…
(abridge version) The evolution of population III stars (Z=0) is followed from the pre-main sequence phase up to the AGB phase for intermediate-mass stars and up to C ignition in more massive stars...We find that, thanks to the development…
New stellar models which track the production and destruction of $^3$He (and D) have been evolved for a range of stellar masses $(0.65\leq M/M_{\odot}\leq 100)$, metallicities $(0.01 \leq Z/Z_{\odot} \leq 1)$ and initial (main sequence)…
Thermohaline mixing has recently been proposed to occur in low mass red giants, with large consequence for the chemical yields of low mass stars. We investigate the role of thermohaline mixing during the evolution of stars between 1 Msun…
The discrepancy between the observed abundances of 3He in the ISM and those predicted by stellar and galactic chemical evolution remains largely unexplained. In this paper, we attempt to shed some light on this unsolved problem by…
Previous theoretical studies suggest that the Population III (Pop3) stars tend to form in extremely metal poor gas clouds with approximately $10^5 M_\odot$ embedded in mini dark matter halos. Very massive stars can form via multiple…
We present the evolutionary models of metal-free stars in the mass range from 0.8 to 1.2 Msun with up-to-date input physics. The evolution is followed to the onset of hydrogen mixing into a convection, driven by the helium flash at red…