Discovery of Interstellar Trans-cyanovinylacetylene (HCCCH=CCHCN) and Vinylcyanoacetylene (H2C=CHC3N) in GOTHAM Observations of TMC-1

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Trans-cyanovinylacetylene

We report the discovery of two unsaturated organic species, trans-(E)-cyanovinylacetylene and vinylcyanoacetylene, using the second data release of the GOTHAM deep survey towards TMC-1 with the 100 m Green Bank Telescope.

For both detections, we performed velocity stacking and matched filter analyses using Markov chain Monte Carlo simulations, and for trans-(E)-cyanovinylacetylene, three rotational lines were observed at low signal-to-noise (∼3σ). From this analysis, we derive column densities of 2×1011 and 3×1011 cm−2 for vinylcyanoacetylene and trans-(E)-cyanovinylacetylene, respectively, and an upper limit of <2×1011 cm−2 for trans-(Z)-cyanovinylacetylene. Comparisons with G3//B3LYP semi-empirical thermochemical calculations indicate abundances of the [H3C5N}] isomers are not consistent with their thermodynamic stability, and instead their abundances are mainly driven by dynamics.

We provide discussion into how these species may be formed in TMC-1, with reference to related species like vinyl cyanide (CH2=CHCN). As part of this discussion, we performed the same analysis for ethyl cyanide (CH3CH2CN), the hydrogenation product of CH2=CHCN. This analysis provides evidence -- at 4.17σ significance -- an upper limit to the column density of <4×1011 cm−2; an order of magnitude lower than previous upper limits towards this source.

Kin Long Kelvin Lee, Ryan A. Loomis, Andrew M. Burkhardt, Ilsa R. Cooke, Ci Xue, Mark A. Siebert, Christopher N. Shingledecker, Anthony Remijan, Steven B. Charnley, Michael C. McCarthy, Brett A. McGuire

Comments: Four figures, two tables. Five supplementary figures and four supplementary tables. Accepted for publication in The Astrophysical Journal Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2101.05858 [astro-ph.GA] (or arXiv:2101.05858v1 [astro-ph.GA] for this version)
Submission history
From: Kin Long Kelvin Lee
[v1] Thu, 14 Jan 2021 20:36:12 UTC (4,395 KB)
https://arxiv.org/abs/2101.05858
Astrobiology, Astrochemistry,

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