A nitrogen-enriched nebula around P Cygni.

Extended nebular emission were detected in [S II] λλ6716, 6731, [N II] λ6584, 6548 and Hα on a long-slit spectrum offset by 9 arcsec from P Cyg. Anomalously strong [Ni II] λ6666.8 emission was also detected. The [S II] doublet ratio yields an electron density of 600 cm −3 . The [N II] and [S II] lines have been used to derive an N/S ratio which is insensitive to the adopted value of electron temperature. The N/S ratio is 33 ± 5 by number, five times higher than solar, implying that the material has undergone CN-cycle processing which has converted most of the original carbon into nitrogen