Vibrationally excited HC 3 N toward hot cores

We report IRAM 30-m observations of vibrationally excited rotational transitions of HC 3 N toward a sample of six ultra–compact Hii regions. In addition, Effelsberg 100-m and Plateau de Bure Interferometer measurements were conducted toward the region G10.47+0.03. We detected the v 7 = 1 state of cyanoacetylene toward all six regions and the v 6 = 1 line toward five of them. Toward G10.47+0.03, we detected lines from 11 different vibrationally excited states with excitation energies up to 1600 K above ground. Of these, six are first detections. We also have detected several transitions of 13 C substituted cyanoacetylene in the v 6 = 1, v 7 = 1, and v 7 = 2 states and provide improved rest frequencies for several of these. The population distribution of the vibrationally excited HC 3 N molecules is analyzed and it is concluded that our results are consistent with thermalised level populations at a temperature of 270 K. From the interferometer results we find the source of HC 3 N emission to be coincident with NH 3 (4,4) and CH 3 CN emission within the positional error of 1. In an appendix, we report the first astronomical detection of lines from vibrationally excited HNCO in G10.47+0.03.