TY - JOUR KW - circumstellar matter KW - stars: massive KW - stars: mass-loss KW - stars: winds KW - outflows KW - stars: Wolf?Rayet?ISM: abundances N1 - This version is the version of record. For information on re-use, please refer to the publisher?s terms and conditions. EP - 3074 IS - 4 AV - public TI - Herschel-PACS measurements of nitrogen enrichment in nebulae around Wolf?Rayet stars A1 - Stock, DJ A1 - Barlow, MJ JF - Monthly Notices of the Royal Astronomical Society PB - OXFORD UNIV PRESS SP - 3065 VL - 441 UR - https://doi.org/10.1093/mnras/stu724 ID - discovery10093774 N2 - For three nebulae that have early-WN Wolf?Rayet exciting stars, NGC 6888, WR 8 and Abell 48, we have obtained Herschel-PACS line scans of the [N?III] 57-?m and [O?III] 88-?m lines, along with the 122- and 205-?m lines of [N?II]. From the former two lines we have derived N2+/O2+ abundance ratios, equal to the overall N/O ratio under a wide range of nebular conditions. We find that all of the nebulae observed possess significant nitrogen enrichment, with derived N/O ratios greater than solar. The two nebulae with massive Wolf?Rayet exciting stars, NGC 6888 and WR 8 are found to have N/O ratios that are enhanced by factors of 7 ? 10 relative to the solar N/O ratio, consistent with an origin as material ejected just before the onset of the Wolf?Rayet phase. The other nebula, Abell 48, has recently been reclassified as a member of the rare class of three planetary nebulae that have early-WN central stars and are not of Peimbert type I. We derive a nebular N/O ratio for it that is a factor of 4 enhanced relative to solar and slightly above the range of N/O values that have been measured for the other three members of its [WN] planetary nebula class. Y1 - 2014/07/11/ ER -