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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We have searched for the emission from \fex and \fexiv that is expected fromthe gas emitting in diffuse X-rays in \bd, NGC 6543, NGC 7009, and NGC 7027.Neither line was detected in any object. Models that fit the X-ray spectra ofthese objects indicate that the \fex emission should be below our detectionthresholds, but the predicted \fexiv emission exceeds our observed upper limits(one sigma) by factors of at least 3.5 to 12. The best explanation for theabsence of \fexiv is that the X-ray plasma is depleted in iron. In principle,this result provides a clear chemical signature that may be used to determinethe origin of the X-ray gas in either the nebular gas or the stellar wind. Atpresent, though various lines of evidence appear to favour a nebular origin,the lack of atmospheric and nebular iron abundances in the objects studied hereprecludes a definitive conclusion.Comment: 23 pages, 4 figure

Iron Depletion in the Hot Bubbles in Planetary Nebulae