Astro-Tomography of Symbiotic Binaries
Abstract
We propose observations of the eclipsing symbiotic system BF-CYG to study the lower levels of the red giant's wind and/or ejected material. This system has been well observed with IUE and has extensive, if sometimes contradictory, literature. IUE observations of BF-CYG show strong evidence for Rayleigh scattering by neutral hydrogen surrounding the M5 III primary, but also show an additional, currently unknown, scattering/opacity component. Our previous experience with FUSE data of the eclipsing symbiotic EG-AND (a system with an earlier spectral type, lower mass loss giant) shows that eclipse mapping is a powerful and sensitive way to determine the amount and nature of the atomic and molecular absorption, and also can lead to surprises (such as the presence of a broad, redshifted white dwarf wind component in the EG-AND case). Unlike massive binaries, the winds of a symbiotic system have very different characteristics -- the hot wind is relatively thin and fast, whereas the cool wind is slow and weakly ionized -- and hence they can be isolated spectroscopically. The far-UV region of the spectrum is rich in a range of permitted and semi-permitted lines ranging from low to high excitation, and also containing the features of molecular hydrogen, thus permitting the diagnosis of material from the base of the giant's wind, them white dwarf wind, and the hot, shocked, material where the two interact. Phase-resolved spectra thus provide the unique tomographic information we require to model these systems and understand how the winds are generated and interact. We have FUSE Cycle 1 data for BF Cyg in an unabsorbed state, so have accurate fluxes and spectra for maximum light, against which we can compare the new observations. In addition, we have proposed to HST for STIS data to maximise the return possible from the combined far-UV/UV spectra.
- Publication:
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FUSE Proposal
- Pub Date:
- 2003
- Bibcode:
- 2003fuse.prop.D174E
- Keywords:
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- FUSE Proposal ID #D174