| Title |
Evoliuciniai cheminės sudėties efektai padrikųjų spiečių raudonosiose milžinėse / |
| Translation of Title |
Evolutionary Effects of Chemical Composition in Red Giants of Open Clusters. |
| Authors |
Mikolaitis, Šarūnas |
| Full Text |
|
| Pages |
39 |
| Keywords [eng] |
Astrophysics ; Stellar evolution ; Open clusters ; Chemical composition |
| Abstract [eng] |
Open clusters are important tools for studying of the Galactic disk and for understanding stellar evolution. Stars of clusters have constant age, composition and distance. This makes them to be excellent laboratories for investigations of stellar and Galactic chemical evolution. The main aim of the study is the analysis of mixing tracers and extra mixing evidences in photospheres of evolved stars. Extra-mixing processes may modify the surface abundances of 12^C/13^C and 12^C/14^N ratios. This study aims to test theoretical models. The secondary goal is a contribution to the study of present properties of the Galactic disc. The 12^C/13^C ratios in helium-core-burning clump stars for the clusters with turn-off masses lower than 2 solar masses are in agreement with the Cool-bottom processing (CBP) model and the Thermohaline mixing (TH) model. The observed 12^C/13^C ratios of the helium-core-burning stars in the open cluster NGC 6134 support evidences of larger then theoretically predicted extra-mixing in stars heavier than 2.5 solar masses. In two open clusters the 12^C/13^C ratios in core-helium-burning stars are lower than in the first ascent giants, located above the RGB luminosity bump. This could be caused by the material mixing during a very violent helium flash event. Almost all element to iron ratios show essentially flat radial abundance distributions across Galactic disk. The radial distributions of [O/Fe] and [Mg/Fe] have a tendency to increase towards larger Galactocentric distances. |
| Type |
Summaries of doctoral thesis |
| Language |
Lithuanian |
| Publication date |
2012 |
