TY  - JOUR
JF  - Monthly Notices of the Royal Astronomical Society
PB  - OXFORD UNIV PRESS
A1  - Stock, DJ
A1  - Barlow, MJ
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/
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
ER  -