2009ApJ...702.1025S

We have conducted millimeter-wave observations of deuterated species of various carbon-chain molecules toward a low-mass star-forming region, L1527, which shows extraordinary richness of carbon-chain molecules in a vicinity of the protostar (Warm Carbon Chain Chemistry; WCCC). We have detected the spectral lines of l-C₃D, C₄D, C₄HD, DC₃N, DC₅N, and c-C₃HD, where l-C₃ D and C₄HD are detected for the first time in space. The deuterium fractionation ratios are found to be moderate (2% to 7%), although they tend to be higher than those in the starless core, TMC-1. The upper limit to the [CH₂DOH]/[CH₃OH] ratio is also as low as 3%. Therefore, high deuterium fractionation ratios reported for hot corino sources are not seen in L1527. The observed ratios mean that the depletion of CO onto dust grains had not proceeded far in L1527, compared to the hot corino case. This would be consistent with a short timescale of the starless core phase, as suggested for the possible origin of WCCC.