G35-26 - Carbon in a peculiar DA white dwarf

G35-26 is the first white dwarf to show atomic lines of both hydrogen and carbon. It should, however, be removed from the list of confirmed magnetic white dwarfs, since any surface field is less than 500,000 gauss. In accordance with the new spectral classification system of Sion et al. (1983), it may be classified as DAQ3. The star could be identified with the hot end of the helium-rich white dwarfs which reveal traces of dredged-up carbon in their atmospheres. It is noted that the absence of nitrogen or heavier element traces in the atmosphere is consistent with this hypothesis. G35-26 would be the hottest star so far to exhibit evidence for this kind of dredging, extending well into the DB temperature range. Since the star shows a high tangential velocity (Greenstein, 1978), it probably had a progenitor mass that was lower than average. In view of the evidence that the final mass may scale with the star's initial mass, the lower white-dwarf mass would allow a convective envelope of larger than normal mass fraction at 15,000 K. In this way, the layer digs deeper into the 'tail' of the carbon core abundance gradient.