Detection of high-excitation rotational lines of cyanoacetylene in the OMC 1 region

Six new high-excitation transitions of cyanoacetylene (HC3N) lying between 209 and 282 GHz have been detected toward OMC 1. Line widths are approx.10 km s-1, broader than the low-frequency HC3N lines. Spectra of two low-frequency (82 and 91 GHz) HC3N transitions with a spatial resolution similar to that of the high-frequency transitions, show both the broad feature and the more commonly seen narrow component. While the low-frequency HC3N transitions are spatially extended in OMC 1, the broad component of the high-frequency HC3N transitions appears to be confined to an unresolved region of approx.1' or less. The intensities of the broad component are used to find the density and temperature of the broad-line-emitting region. The best fit to the HC3N line intensities yields T/sub K/ = 125 K and a density of > or =107 cm-3