TY - JOUR
T1 - Identification of KCN in IRC+10216
T2 - Evidence for selective cyanide chemistry
AU - Pulliam, R. L.
AU - Savage, C.
AU - Agúndez, M.
AU - Cernicharo, J.
AU - Guélin, M.
AU - Ziurys, L. M.
PY - 2010/12/20
Y1 - 2010/12/20
N2 - A new interstellar molecule, KCN, has been identified toward the circumstellar envelope of the carbon-rich asymptotic giant branch star, IRC+10216 - the fifthmetal cyanide species to be detected in space. Fourteen rotational transitions of this T-shaped, asymmetric top were searched for in the frequency range of 83-250 GHz using the Arizona Radio Observatory (ARO) 12 m Kitt Peak antenna, the IRAM 30 m telescope, and the ARO Submillimeter Telescope. Distinct lines were measured for 10 of these transitions, including the K a = 1 and 2 asymmetry components of the J = 11→10 and J = 10→9 transitions, i.e., the K-ladder structure distinct to an asymmetric top. These data are some of themost sensitive astronomical spectra at λ∼1 and 3mmobtained to date, with 3σ noise levels ∼0.3 mK, made possible by new ALMA technology. The line profiles from the ARO and IRAM telescopes are consistent with a shell-like distribution for KCN with r outer ∼ 15″, but with an inner shell radius that extends into warmer gas. The column density for KCN in IRC+10216 was found to be N tot ≈ 1.0×1012 cm-2 with a rotational temperature of Trot ∼ 53 K. The fractional abundance was calculated to be f(KCN/H2) ∼ 6×10-10, comparable to that of KCl. The presence of KCN in IRC+10216, along with MgNC, MgCN, NaCN, and AlNC, suggests that cyanide/isocyanide species are the most common metal-containing molecules in carbon-rich circumstellar gas.
AB - A new interstellar molecule, KCN, has been identified toward the circumstellar envelope of the carbon-rich asymptotic giant branch star, IRC+10216 - the fifthmetal cyanide species to be detected in space. Fourteen rotational transitions of this T-shaped, asymmetric top were searched for in the frequency range of 83-250 GHz using the Arizona Radio Observatory (ARO) 12 m Kitt Peak antenna, the IRAM 30 m telescope, and the ARO Submillimeter Telescope. Distinct lines were measured for 10 of these transitions, including the K a = 1 and 2 asymmetry components of the J = 11→10 and J = 10→9 transitions, i.e., the K-ladder structure distinct to an asymmetric top. These data are some of themost sensitive astronomical spectra at λ∼1 and 3mmobtained to date, with 3σ noise levels ∼0.3 mK, made possible by new ALMA technology. The line profiles from the ARO and IRAM telescopes are consistent with a shell-like distribution for KCN with r outer ∼ 15″, but with an inner shell radius that extends into warmer gas. The column density for KCN in IRC+10216 was found to be N tot ≈ 1.0×1012 cm-2 with a rotational temperature of Trot ∼ 53 K. The fractional abundance was calculated to be f(KCN/H2) ∼ 6×10-10, comparable to that of KCl. The presence of KCN in IRC+10216, along with MgNC, MgCN, NaCN, and AlNC, suggests that cyanide/isocyanide species are the most common metal-containing molecules in carbon-rich circumstellar gas.
KW - Astrochemistry
KW - Circumstellar matter
KW - Line: identification
KW - Stars: AGB and post-AGB
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U2 - 10.1088/2041-8205/725/2/L181
DO - 10.1088/2041-8205/725/2/L181
M3 - Article
AN - SCOPUS:78650231864
SN - 2041-8205
VL - 725
SP - L181-L185
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2 PART 2
ER -