Is There Evidence for Rotation or Horizontal Motions in Hot DB White Dwarfs?

Abstract

In a recent analysis of Goddard High Resolution Spectrograph observations of three hot DB white dwarfs, Provencal et al. suggested that the C II λ1335 doublet in two such objects is abnormally broadened. This was interpreted as the signature of rotation, or perhaps of pulsation-related horizontal motions, at a velocity of v~60kms^-1. Our reanalysis of these observations shows that a self-consistent analysis of the observed C II profiles is possible without calling on additional broadening mechanisms. There is thus currently no evidence for significant rotation velocities or horizontal motions in hot DB white dwarfs.