2017ApJ...847...51A

Long carbon-chain molecules were searched for toward the low-mass star-forming region L1527, which is a prototypical source of warm carbon-chain chemistry (WCCC), using the 100 m Green Bank Telescope. Long carbon-chain molecules, C₇H (²Π_1/2), C₆H (²Π_3/2 and ²Π_1/2), CH₃C₄H, and C₆H₂ (cumulene carbene, CCCCCCH₂), and cyclic species of C₃H and C₃H₂O were detected. In particular, C₇H was detected for the first time in molecular clouds. The column density of C₇H is determined to be 6 x 10¹⁰ cm^–2. The column densities of the carbon-chain molecules including CH₃C₄H and C₆H in L1527 relative to those in the starless dark cloud Taurus Molecular Cloud-1 Cyanopolyyne Peak (TMC-1 CP) tend to be systematically lower for long carbon-chain lengths. However, the column densities of C₇H and C₆H₂ do not follow this trend and are found to be relatively abundant in L1527. This result implies that these long carbon-chain molecules are remnants of the cold starless phase. The results-that both the remnants and WCCC products are observed toward L1527-are consistent with the suggestion that the protostar can also be born in the parent core at a relatively early stage in the chemical evolution.