Observation and analysis of variable linear polarization in the yellow supergiant star Epsilon Aurigae
Epsilon Aurigae is an extremely long period eclipsing binary system whose primary component is a yellow supergiant star. The nature of the secondary component is uncertain, but it is believed to be a disk of cool dust and gas, possibly surrounding an unseen young hot star or binary star. The yellow supergiant is known to be an irregular long period variable star and the variability is considered to be the result of pulsations, the characteristics of which are unknown. Linear polarization measurements in U, B, and V filters were obtained over a four year period to investigate the possibility of a relationship between the variable polarization and pulsation modes in the star. A comparison with contemporaneous photometric observations was made to look for correlations between the light and polarization changes. A period analysis revealed no strict periodicities in the data although variations with a time scale on the order of 100 days were observed. The behavior of the polarization variations during cycles of maxima and minima in the light curve closely fit model predictions for nonradial pulsation. Changes in the direction of the major axis of the polarization variations strongly suggests the presence of at least two modes in the star at different times and perhaps even simultaneously. Although a definite mode or modes could not be identified, the variations were best interpreted as due to modes with l = 2 or l = 3. Also, rectilinear patterns of the polarization variations on the Q, U plane indicate that the inclination of the star's rotation axis is large, near 90 deg.
- Research Organization:
- Oregon Univ., Eugene, OR (USA)
- OSTI ID:
- 6164305
- Resource Relation:
- Other Information: Ph.D. Thesis
- Country of Publication:
- United States
- Language:
- English
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