Abstract
Detections of extragalactic N-15 are reported from observations of the rare hydrogen cyanide isotope (HCN)-N-15 reward the Large Magellanic Cloud (LMC) and the core of the (post-)starburst galaxy NGC 4945. Accounting for optical depth effects, the LMC data from the massive star-forming region N113 infer an N-14/N-15 ratio of 111 +/- 17, which is about twice the C-12/C-13 value. For the LMC star-forming region N159HW and for the central region of NGC 4945, N-14/N-15 ratios are also approximate to 100. The N-14/N-15 ratios are smaller than all interstellar nitrogen isotope ratios measured in the disk and center of the Milky Way, strongly supporting the idea that N-15 is synthesized by massive stars. Although this appears to be in contradiction with standard stellar evolution and nucleosynthesis calculations, it supports recent findings of abundant N-15 production due to rotationally induced mixing of protons into the helium-burning shells of massive stars.