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

The controversy on the time variation of the radial abundance gradients canin principle be settled by estimating the gradients from planetary nebulae (PN)ejected by central stars (CSPN) with different ages. In this work, we considerfour samples of CSPN whose lifetimes have been estimated using three differentmethods and estimate the oxygen abundance gradients for these objects. Theresults suggest some small differences between the younger and older CSPN. Theyounger objects have similar or slightly higher oxygen abundances compared withthe older objects, and the gradients of both groups are similar within theuncertainties. Therefore, the O/H radial gradient has not changed appreciablyduring the lifetime of the objects considered, so that PN gradients are notexpected to be very different from the gradients observed in younger objects,which seems to be supported by recent observational data.

Time variation of the O/H radial gradient in the galactic disk based on planetary nebulae