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Title: A multiwavelength abundance analysis of sdB stars using new model atmospheres
Author: Pereira, Caroline
ISNI:       0000 0004 2726 5906
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2011
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SdB stars provide a number of challenges in stellar astronomy. Their evolution along the extreme horizontal branch is well-known, but their formation remains a uncertain. Moreover, sdB stars show peculiar photospheric abundances due to diffusion processes and non-radial oscillation have been detected in approximately 10% of sdB stars. Thus, improved knowledge of fundamental parameters of sdB stars through high-quality observations and improved modelling, will allow us to gain a better understanding of these stars, and eventually help address these issues. We have carried out a detailed abundance analysis on a sample of sdB stars, using high quality multiwavelength spectroscopic data from optical telescopes and the HST/STIS and FUSE satellites. The multiwavelength approach allows us verify the consistency of our derived atmospheric parameters, and also allows us to probe elemental abundances of species not readily accessible in the optical region. In addition, we have also used the latest generation of LTE models which implement full metalline blanketing, opacity sampling and updated opacity values from the Opacity Project and IRON Project. Our model grids included OS_m1O models, where abundances were scaled to one-tenth of solar values (as is normally used in sdB studies), and OS_sdB models, where Z < 20 are underabundant by a factor of ten, and Z ~ 20 are overahundant by a factor of ten with respect to solar values. Finally, we have compared our results over the three wavelength regions, to verify the consistency, and we have tri'ed to find any correlations between abundances and sdB properties such as pulsation and evolution.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available