English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Analyses of large spectroscopic surveys of early-type stars in the LMC havefound an excess of nitrogen enriched B-type targets with a vsini<40 km/scompared with the predictions of single star evolutionary models incorporatingrotational mixing. By contrast the number of such targets with 40<vsini<80 km/swere consistent with such models. We have undertaken a similar analysis for 61B-type similar targets, towards the young cluster, NGC 346 in the SmallMagellanic Cloud (SMC). Approximately 65% could have nitrogen enhancements ofless than 0.3 dex, consistent with them having experienced only small amountsof mixing due to their low rotational velocities. However as with the previousLMC surveys, an excess of stars with low projected rotational velocities,vsini<40 km/s and significant nitrogen enrichments is found. This is estimatedto be approximately 5% of the total population of apparently single B-typestars or 40% of all stars with current rotational velocities of less than 40km/s. For all three surveys, the presence of undetected binaries and otheruncertainties imply that these percentages might be underestimated and indeedit is possible that all single stars with current rotational velocities of lessthan 40 km/s are nitrogen enriched. Possible explanations incorporate theeffects of magnetic fields, via either a stellar merger followed by magneticbreaking or the evolution of a single star with a large magnetic field. Bothmechanisms are compatible with the observed frequency of nitrogen-enrichedstars in the Magellanic Clouds. Differences in the properties of thenitrogen-enriched stars compared with the remainder of the sample would beconsistent with the former mechanism. For the latter, a qualitative comparisonwith evolutionary models incorporating magnetic fields is encouraging in termsof the amount of nitrogen enrichment and its presence in stars near the ZAMS.

The NGC 346 massive star census: Nitrogen abundances for apparently single, narrow lined, hydrogen core burning B-type stars