- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- Evolutionary and pulsational models of metal-poor subdwarfs
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
Evolutionary and pulsational models of metal-poor subdwarfs Shkolnik, Evgenya
Abstract
Metal-poor subdwarfs (MPSDs) are probably the Sun's oldest neighbours and are almost certainly low-amplitude p-mode pulsators, like the Sun. One of the goals of the MOST Space Telescope project (due for launch in 2002 - 2003) is to detect MPSD oscillations and apply asteroseismology to refine the calibration of globular cluster isochrone fitting and possibly set a lower limit to the age of the Universe. To be able to interpret the eigenfrequency data, a comprehensive grid of nonadiabatic, nonradial pulsation models for MPSDs was generated for the first time using a code developed by Guenther (1994). Each pulsation model was calculated from a structural evolutionary model using the Yale Stellar Evolution Code with Rotation (YREC) which included up-to-date physics such as both He and heavy element diffusion and the latest EOS and opacity tables. The grid spanned the following ranges: helium abundance Y = 0.235 to 0.255 (consistent with estimates of primordial Y); heavy element abundance Z = 0.0002 to 0.01 (consistent with MPSD spectra); mass M = 0.7 to 1.0 M[sub o] ; and age A = 5 to 16 Gyr. From the calculated eigenfrequencies of each model, the large and small frequency spacings (Δ v, δV[sub0,2]) were derived as defined by asymptotic pulsation theory (Tassoul 1980). These spacings are sensitive diagnostics of the mass and mainsequence age of the star. Combining MOST's resolution with the uncertainties in the input parameters, MOST data could refine MPSD ages to better than ± 0.056 Gyr (an average error assuming the input physics are correct).
Item Metadata
Title |
Evolutionary and pulsational models of metal-poor subdwarfs
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
2000
|
Description |
Metal-poor subdwarfs (MPSDs) are probably the Sun's oldest neighbours and are almost
certainly low-amplitude p-mode pulsators, like the Sun. One of the goals of the MOST
Space Telescope project (due for launch in 2002 - 2003) is to detect MPSD oscillations
and apply asteroseismology to refine the calibration of globular cluster isochrone fitting
and possibly set a lower limit to the age of the Universe.
To be able to interpret the eigenfrequency data, a comprehensive grid of
nonadiabatic, nonradial pulsation models for MPSDs was generated for the first time
using a code developed by Guenther (1994). Each pulsation model was calculated from
a structural evolutionary model using the Yale Stellar Evolution Code with Rotation
(YREC) which included up-to-date physics such as both He and heavy element diffusion
and the latest EOS and opacity tables. The grid spanned the following ranges: helium
abundance Y = 0.235 to 0.255 (consistent with estimates of primordial Y); heavy element
abundance Z = 0.0002 to 0.01 (consistent with MPSD spectra); mass M = 0.7 to 1.0 M[sub o] ;
and age A = 5 to 16 Gyr. From the calculated eigenfrequencies of each model, the large
and small frequency spacings (Δ v, δV[sub0,2]) were derived as defined by asymptotic pulsation
theory (Tassoul 1980). These spacings are sensitive diagnostics of the mass and mainsequence
age of the star. Combining MOST's resolution with the uncertainties in the
input parameters, MOST data could refine MPSD ages to better than ± 0.056 Gyr (an
average error assuming the input physics are correct).
|
Extent |
6156538 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-07-20
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
|
DOI |
10.14288/1.0099563
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
2000-11
|
Campus | |
Scholarly Level |
Graduate
|
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.