FUSE Observations of long-period pulsators among subdwarf B stars
Abstract
We propose FUSE observations of a sample of 13 cool subdwarf B stars known to exhibit very low amplitude (lta 5 millimag), long-period 1000-5000 s), multiperiodic luminosity variations (the PG 1716 stars). These variations are interpreted as high radial order g modes. Current numbers indicate that the cool PG 1716 pulsators are much more common than their hotter counterparts, the shorter period EC 4026 stars discovered several years ago in the region below 28,000 K where the long-period pulsators are found, it may well be that all sdB stars are variable, a results that contrasts with the observed lack of purity of the instability strip of the EC 14026 stars. Despite these important differences, it has been suggested that the driving mechanism operating in the long-period variables is the same as that thought to operate in the EC 14026 stars driving is linked to the opacity bump associated with a local enhancement of the iron abundance in the envelope brought about by radiative forces on that element. Abundance analyses of PG 1716 stars based on FUSE observations will permit a test of these ideas. Specifically, we will investigate whether the atmospheric abundance of iron peak elements is i) consistent with that required to drive the pulsations in the PG 1716 stars and ii) sufficiently homogeneous among the PG 1716 stars to account for the statistics of variable vs. non variable stars among cool sdB stars.
- Publication:
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FUSE Proposal
- Pub Date:
- 2004
- Bibcode:
- 2004fuse.prop.E122W
- Keywords:
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- FUSE Proposal ID #E122