SIMBAD references

The rotational spectral lines (J_N=3₂-2₁ and J_N=2₁-1₀) of ¹³CCS and C¹³CS have been observed toward a cold dark cloud, TMC-1. The strongest hyperfine component lines of ¹³CCS and C¹³CS (J_N=2₁-1₀, F=5/2-3/2) have successfully been detected. The C¹³CS/¹³CCS abundance ratio is determined to be 4.2±2.3 (3 σ). The CCS/¹³CCS ratio is evaluated to be 230±130 (3 σ), and hence, ¹³CCS is found to be significantly diluted. Such a difference between the ¹³CCS and C¹³CS abundances is also found in L1521E, which is a very young core with rich carbon-chain molecules. Therefore, the anomaly is not specific to TMC-1, but seems to be common for the CCS-rich clouds. Furthermore, we have also observed the J=4-3 transition of ¹³CCCS and CCC³⁴S in TMC-1 and L1521E and have found that the CCC³⁴S/¹³CCCS ratio is larger than 8.4 (3 σ). This lower limit is considerably larger than the interstellar ¹²C³⁴S/¹³C³²S ratio of 3, indicating that ¹³CCCS is diluted as in the case of ¹³CCS. These results give us strong constraints on the main pathways to produce CCS and CCCS.