相关论文: On the Blue Loops of Intermediate-Mass Stars
Based on the turbulent convection model (TCM), we investigate chemical mixing in the bottom overshooting region of the convective envelope of intermediate-mass stars, focusing on its influence on the formation and extension of blue loops in…
The core helium-flash in low-mass stars with extreme mass loss occurs after the tip of the RGB, when the H-rich envelope is very thin. The low efficiency of the H-shell source enables the He-flash driven convective zone to penetrate H-rich…
In this paper, four sets of evolutionary models are computed with different values of the mixing length parameter $\alpha_{\rm p}$ and the overshooting parameter $\delta_{\rm ov}$. The properties of the convective cores and the convective…
During the post-main sequence evolution massive stars pass through several short-lived phases, in which they experience enhanced mass loss in the form of clumped winds and mass ejection events of unclear origin. The discovery that stars…
The evolution of low- and intermediate mass stars at the onset and during core helium burning is reviewed. Particular emphasis is laid on structural differences, which may allow to identify a star's nature and evolutionary phase in spite of…
We construct a speculative scenario for rotation-induced extra helium mixing to the envelope of horizontal branch (HB) stars. This scenario differs from previous ones in that the mixing occurs after the star has left the red giant branch…
Evolutionary tracks and pulsational analysis of models with masses of 13-18 $M_\odot$ are presented. We address two important questions. The first one deals with one of the most unresolved problems in astrophysics, i.e., the existence of a…
We examine the convective core helium burning phase of intermediate mass stars, and investigate the role of coupling of nuclear burning and mixing on the extension and duration of the blue loop phase. We compare the theoretical scenario…
The distribution of stars in the Hertzsprung Russell diagram (HRD) for a stellar conglomeration represents a snapshot of its evolving stellar population. Some of the supergiant stars may transit the HRD from blue to red and then again to…
Red Clump stars have been found to be enhanced in lithium relative to stars at the tip of the Red Giant Branch (TRGB), which is unexpected in current stellar models. At the TRGB, stars undergo the helium flash, during which helium burning…
We assume that the strong convection during core helium flash of low mass red giant branch (RBG) stars excite waves that propagate to the envelope, and find that the energy that these waves deposit in the envelope causes envelope expansion…
The observed abundance variations in globular cluster red giants indicate that these stars may be mixing helium from the hydrogen shell outward into the envelope, presumably as a result of internal rotation. We have investigated the…
We briefly review the main problems related to the computation of the evolution of intermediate-mass stars: the treatment of turbulent convection and the occurrence of blue loops during the core He-burning phase. It is shown that, in order…
Core helium burning is the dominant source of energy of extreme horizontal branch stars, as the hydrogen envelope is too small to contribute to the nuclear energy output. The evolution of each mass in the HR diagram occurs along vertical…
Shell convection driven by nuclear burning in a stellar core is a common hydrodynamic event in the evolution of many types of stars. We encounter and simulate this convection (i) in the helium core of a low-mass red giant during core helium…
We present detailed evolutionary calculations focused on the evolution of intermediate mass stars with 3 Msun < M < 9 Msun of metallicity typical of the Large Magellanic Cloud (LMC), i.e. Z=0.008. We compare carefully the models calculated…
A new mechanism for enhancing the helium abundance in the blue main sequence stars of omega Centauri and NGC 2808 is investigated. We suggest that helium enhancement was caused by the inhomogeneous big bang nucleosynthesis. Regions with…
It has been known for a long time that some red giants in globular clusters exhibit large star-to-star variations in the abundances of light elements that are not exhibited by field giants. This fact can be taken as evidence that the extra…
Intermediate-mass stars end their lives by ejecting the bulk of their envelope via a slow dense wind back into the interstellar medium, to form the next generation of stars and planets. Stellar pulsations are thought to elevate gas to an…
Convection in the cores of massive stars becomes anisotropic when they rotate. This anisotropy leads to a misalignment of the thermal gradient and the thermal flux, which in turn results in baroclinicity and circulation currents in the…