Statistics – Computation
Scientific paper
Dec 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996phdt.......108s&link_type=abstract
PhD Thesis, Laboratoire d'Astrophysique, Observatoire de Grenoble, Université Joseph Fourier, BP 53, F--38041 Grenoble Cedex 9,
Statistics
Computation
Scientific paper
The stellar structure and evolution of low- and intermediate-mass stars is investigated in a context where the star is gaining mass from a circumstellar accretion disk. The first part of this work, dedicated to standard evolution, presents new evolutionary models for pre-main sequence stars. These new computations are used to generate synthetic HR diagrams. We show that such a tool is well suited to reproduce the morphology of young clusters and allow to derive some physical parameters prevailing in these clusters such as the binarity rate or the duration of the star forming process. The second part describes the stellar evolutionary code and the accretion model which determines how the accreted matter distributes inside the star. The formalism of the model is based on the Richardson criterion and takes into account the mechanical, thermal and chemical properties of the accreted matter. Numerical results indicate that accreted matter easily crosses the radiative atmosphere and that convection favors a rather uniform distribution of the accreted matter in the stellar interior. The last part is devoted to the influence of the accretion process on stellar structure and evolution. Computations show that deuterium nuclear burning plays a crucial role during the pre-main sequence phase. For a specified range of accretion rates, we observe a expansion of the star along its Hayashi line. For higher accretion rates, characteristic of the star forming phase, we reproduce the birthline which represents an upper envelope of the pre-main sequence stellar distribution. Finally, we compare the structural and evolutionary differences between accreting and non-accreting tracks. We show that the arrival of accreted matter accelerates the star contraction on the Hayashi branch and, from its position in the HR diagram, an accreting star appears younger than in a standard scheme. We also analyze the influence of accretion on surface stellar abundances of light elements such as deuterium and lithium. We determine the areas in the HR diagram where accretion significantly increases the abundances of these elements. Finally, we illustrate the opportunities this accretion model opens to the study of the stellar rotational evolution.
No associations
LandOfFree
Evolution of Young Stars. Physics and Modeling of Accretion does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Evolution of Young Stars. Physics and Modeling of Accretion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evolution of Young Stars. Physics and Modeling of Accretion will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1171157