August 1, 2012.
Asymptotic Giant Branch (AGB) stars are in a later stage of life than stars like our Sun. these stars are beginning to shed their outer layer and will eventually form planetary nebulae (PNe). The evolution of a PN impacts the evolution of the surrounding galactic environment, but PNe often have asymmetric geometries which are not entirely understood. The influence of a binary companion is predicted to affect the evolution of a PN although it is difficult to detect companions around AGB stars due to their dusty envelopes, large luminosities and variability. material shed by AGB stars however would likely form a disk of matter surrounding the companion, much as is observed in the mira system. if the companion is hotter than the GB star, the radiation from the companion would cause the disk to emit far ultraviolet (FUV) radiation in excess of what would be given off by an AGB star (and its surrounding envelope) due to the AGB star's lower temperature. 12 objects were identified for study based on UV, IR and optical blackbody data which indicated the likely presence of hotter companion stars. Spectroscopic UV data was then obtained by GALEX to search for characteristic spectral features typical of known AGB binary systems. The resulting "peek" into these systems however is relatively inconclusive due to missing FUV data for all but one object (resulting from an instrument failure) combined with the lower resolution of the GALEX grism. Future observations by the Cosmic origins Spectrograph (COS) on the Hubble Space Telescope are recommended to further prove these systems.
NASA Jet Propulsion Laboratory (JPL)
This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013 and Grant No. 0833353. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).