The unusual carbon star HD 59643 : alternative models.

Abstract

The authors discuss a binary model for the star in which the secondary spectrum is formed in an accretion disk. If this hot, ultraviolet-emitting disk radiates like a 20,000K black-body, it must be ≤0.03 R_sun; across at minimum emission. Large widths of C IV multiplet UV1 on high-resolution spectra indicate its formation in the inner parts of a disk. The C III] and Si III] lines, however, are much narrower (65 km s^-1 FWHM) and could be formed in the outer parts of a disk or in the carbon star's chromosphere. The electron density in the region of formation of C III] is ≡10¹⁰cm^-3.