SIMBAD references

We present the discovery in TMC-1 of vinyl acetylene, CH₂CHCCH, and the detection, for the first time in a cold dark cloud, of HCCN, HC₄N, and CH₃CH₂CN. A tentative detection of CH₃CH₂CCH is also reported. The column density of vinyl acetylene is (1.2±0.2)x10¹³cm^–2, which makes it one of the most abundant closed-shell hydrocarbons detected in TMC-1. Its abundance is only three times lower than that of propylene, CH₃CHCH₂. The column densities derived for HCCN and HC₄N are (4.4±0.4)x10¹¹cm^–2 and (3.7±0.4)x10¹¹cm^–2, respectively. Hence, the HCCN/HC₄N abundance ratio is 1.2± 0.3. For ethyl cyanide we derive a column density of (1.1±0.3)x10¹¹cm^–2. These results are compared with a state-of-the-art chemical model of TMC-1, which is able to account for the observed abundances of these molecules through gas-phase chemical routes.