The Astronomical Journal
We present a high-resolution ultraviolet spectrum of the helium-rich degenerate LDS 678A, obtained with the International Ultraviolet Explorer (IUE) satellite. LDS 678A is the coolest metallic line degenerate (DQ or DZ) yet observed with the IUE echelle. These observations provide a detailed line profile of the strong C I 2479 absorption line and equivalent width W₂₄₇₉ = 2.35 ± 0.06 Å from which theoretical profile fits yield a carbon abundance of log C/He = (-6.7 ± 0.2). The presence of carbon in a Herich atmosphere lends credence to the notion that LDS 678A is a transitional case between the DB white dwarfs with nearly pure helium atmospheres and the helium-rich DQ white dwarfs which exhibit carbon bands. Corrected for an inferred pressure shift Vp = +38 ± 4 km/s for the C I 2479 line, a gravitational redshift of Vrs = + 26 ± 13 km/s is deduced from which a most probable mass of 0.55script M sign⊙ is derived.
Oswalt, Terry D.; Sion, Edward M.; Hammond, Gordon; Liebert, James W.; Wegner, Gary; Koester, Detlev; and Marcum, Pamela M., "UV Observations Of The Cool DBQA5 White Dwarf LDS 678A: Limits On The Atmospheric Composition, Pressure Shift, And Gravitational Redshift Derived From C I 2479" (1991). Aerospace, Physics, and Space Science Faculty Publications. 206.