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13 C Isotopic Fractionation of HC 3 N in Two Starless Cores: L1521B and L134N (L183)

2017; IOP Publishing; Volume: 846; Issue: 1 Linguagem: Inglês

10.3847/1538-4357/aa82ba

1538-4357

Kotomi Taniguchi, Hiroyuki Ozeki, Masao Saito,

Atmospheric Ozone and Climate

Abstract We observed the <?CDATA $J=5-4$?> rotational lines of the normal species and three 13 C isotopologues of HC 3 N at the 45 GHz band toward two low-mass starless cores, L1521B and L134N (L183), using the Nobeyama 45 m radio telescope in order to study the main formation pathways of HC 3 N in each core. The abundance ratios of the three 13 C isotopologues in L1521B are derived to be [H 13 CCCN]:[HC 13 CCN]:[HCC 13 CN] = 0.98 (±0.14):1.00:1.52 (±0.16) ( <?CDATA $1\sigma $?> ). The fractionation pattern is consistent with that at the cyanopolyyne peak in Taurus Molecular Cloud-1. This fractionation pattern suggests that the main formation pathway of HC 3 N is the neutral–neutral reaction between C 2 H 2 and CN. On the other hand, their abundance ratios in L134N are found to be [H 13 CCCN]:[HC 13 CCN]:[HCC 13 CN] = 1.5 (±0.2):1.0:2.1 (±0.4) ( <?CDATA $1\sigma $?> ), which are different from those in L1521B. From this fractionation pattern, we propose that the reaction between HNC and CCH is a possible main formation pathway of HC 3 N in L134N. We find out that the main formation pathways of the same molecule are not common even in similar physical conditions. We discuss the possible factors that could make a difference in the fractionation pattern between L134N and L1521B/TMC-1.