Faint Object Camera (FOC) images from the Hubble Space Telescope are presented showing a clean spatial separation of the two giants in the Capella system (α Aur, HD 34029). These images were taken at elongation (Dec. 21, 1997) when the apparent separation of the stars, 55 milliarcseconds, corresponded to 4 pixels in the FOC image. Careful use of the objective prism mode of the FOC yielded ultraviolet spectra with dispersion perpendicular to the axis of separation of the two stars. The relative flux contributions to prominent UV emission lines such as O I λ 1305, C II λ 1335 and Si IV λ 1397 can then be derived. This direct measurement of each star's emission can be compared to the total spectrum as obtained by STIS at a similar phase (Sept. 12, 1999) where multiple gaussian fitting must be invoked to separate the individual contributions. The relation of these ratios to the known evolutionary states of the two stars, and the consequences for theories of stellar magnetic dynamos are discussed. This research is supported in part by an STScI Grant to SAO.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1999