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Detection of C8H- and Comparison With C8H Toward IRC+10216 With the Green Bank Telescope



A Remijan, J M. Hollis, Francis J. Lovas, M A. Cordiner, J Millar, A J. Markwick-Kemper, P R. Jewell


We report the detection of new transitions of octatetraynyl(C8H) toward the circumstellar envelopeIRC+10216 using data taken with the RobertC.Byrd 100m Green Bank Telescope(GBT). In addition, we report 5 transitions from Ku-, K- and Q-band that have been identified as the J = 22-21, 35-34, 36-35, 37-36 and 38 - 37 transitions of the octatetraynylide ion(C8H-). From a rotational temperature diagram and an assumed source size of 30 , we find a total C8H column density of 8(3) 1012 cm-2 and a rotational temperature of 13 K. From the 5 detected transitions of C8H-, we find a total C8H- column density of 2(2) 1012 cm-2 and a rotational temperature of 52K for a total C8H/C8H- column density ratio of 4. This observed C8H/C8H- column density ratio is similar to the theoretical prediction of 3.6(Millar et al. 2007) while the observed column densities were lower than that predicted by a factor of 30. This prompted us to re-investigate the initial conditions of the circumstellar envelope (CSE) model. The new model results are presented which more closely match the observed C8H and C8H- abundances observed with the GBT. Finally, we use the new CSE model results to predicted the abundance of decapentaynyl (C10H), and compare with the measured upper limit found from the GBT observations.
Astrophysical Journal


abundances, circumstellar species, microwave spectra, molecular spectra, octatetraynylide ion, radioastronomy


Remijan, A. , Hollis, J. , Lovas, F. , Cordiner, M. , Millar, J. , Markwick-Kemper, A. and Jewell, P. (2007), Detection of C<sub>8</sub>H<sup>-</sup> and Comparison With C<sub>8</sub>H Toward IRC+10216 With the Green Bank Telescope, Astrophysical Journal, [online], (Accessed April 17, 2024)
Created June 26, 2007, Updated October 12, 2021