CARBON AND OXYGEN DEPLETION AND EXTINCTION IN THE TRANSLUCENT CLOUD TOWARD HD-24534 (X-PERSEI)

Recent studies of the gas-phase abundances of carbon and oxygen in dif fuse clouds have suggested that the depletions of both elements are in variant and independent of extinction curve properties. We show, howev er, that in the line of sight toward HD 24534 (X Persei), the depletio n of carbon is at least a factor of 3 greater than in the diffuse clou ds previously surveyed. For HD 24534, the interstellar gas-phase C/H r atio is lower than the mean of diffuse sight lines by a factor of abou t 3.5. We conclude that the carbon depletion may be enhanced in transl ucent molecular clouds and also that carbon begins to show an enhanced level of depletion at lower extinctions than oxygen, which is also di scussed. We argue that it is imperative to measure abundances and depl etions in translucent and denser clouds in order to understand the int eraction between gas and dust as the thicknesses and densities of clou ds increase.