Other
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21542521g&link_type=abstract
American Astronomical Society, AAS Meeting #215, #425.21; Bulletin of the American Astronomical Society, Vol. 42, p.339
Other
Scientific paper
The Barium dwarfs are chemically peculiar F- and G-type stars that show enhanced abundances of s-process elements such as strontium and barium. They are believed to have derived their chemical peculiarities via mass transfer from a former AGB companion, now a white dwarf. These WD companions should be detectable in the far-ultraviolet if their effective temperatures exceed 10,000K. However, despite dedicated IUE searches, no WD companion has been directly detected. We have observed 4 Ba dwarfs with the GALEX ultraviolet space telescope (2 newly discovered Ba dwarfs have archival observations), and report here on the first unequivocal direct detection of a WD companion of a Ba dwarf, HD 15306, the hottest Ba dwarf known (F4 V). This WD companion is detected through a clear far-ultraviolet excess. Detection of the putative WD companions of the other observed Ba dwarfs is somewhat more problematical, as those stars have cooler effective temperatures and chromospheric activity can significantly affect their FUV fluxes. The disentanglement of WD FUV fluxes from FUV emission due to chromospheric activity requires comparison of the observed Ba dwarfs with F- and G-type dwarfs with archival GALEX photometry. We have selected a set of 68 F- and G-type dwarfs from the NStars program (Gray et al. 2003, 2006) that have good quality archival GALEX photometry and show a wide range of chromospheric activity. A comparison of these stars with the 5 remaining GALEX-observed Ba dwarfs suggests that one and perhaps two of these Ba dwarfs have detectable WD companions.
Corbally Christopher J.
Gray Richard O.
Griffin Elizabeth
McGahee C. E.
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