Physical and chemical structure of the IC 63 nebula .3. Gas-phase carbon abundance

Observations of the 609 mu m line of atomic carbon, the 158 mu m line of ionized carbon, and multiple high-J transitions of the CO molecule and its isotopes are presented for the reflection / emission nebula IC 63. All important gas-phase forms of carbon have therefore been measured, enabling an accurate determination of the carbon abundance in the gas-phase in this well defined cloud. We find that the gas-phase fraction of carbon in IC 63 is only 13(-4)(+6)% of the solar abundance, significantly lower than found in diffuse clouds and in some dense clouds.