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ER Del: A True Symbiotic S Star?

Published online by Cambridge University Press:  12 April 2016

Hollis R. Johnson  and
Thomas B. Ake
Hollis R. Johnson
Affiliation:
Indiana University
Thomas B. Ake
Affiliation:
Space Telescope Sci. Inst./CSC

Extract

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ER Del = BD+8:4506 is a faint (m ≈ 10) irregularly variable PRG star classified spectral type S5.5/2.5 (Ake 1979). Spectra show H alpha in emission and a strong UV continuum with emission lines of C IV, Si III], and C III] — characteristic of symbiotic-like stars. Although a few other MS and S stars have hot companions, this is the first to show hydrogen emission lines in the optical region. It has been suggested (Smith & Lambert 1986; Little et al. 1987) that all Tc-deficient PRG stars are accidental; that is, they arose by mass transfer when the currently degenerate companion was itself an AGB star. Indeed, the Tc-deficient S stars HR 1105 (Ake, Johnson and Peery 1988) and HD 35155 (Ake and Johnson 1988) and the R8 star HD 59643 (Johnson et al. 1988) not only have hot, subluminous companions, but also are interacting systems - a sign the components are close enough for mass transfer to have occurred. An accretion disk is probably present.

Type
5. Chromospheres, Winds and Mass Loss
Information
International Astronomical Union Colloquium , Volume 106: Evolution of Peculiar Red Giant Stars , 1989 , pp. 371
Copyright
Copyright © Cambridge University Press 1989

References

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