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 obtained observations of the planetary nebula K648 in the Galacticglobular cluster M15 with the Hubble Space Telescope's WFPC2 camera, coveringan interval of 7 days. The frames provide both time-sampled broad-bandphotometry of the central star and high-resolution images of the nebula in thelight of H-alpha, [OIII], and [NII]. In the deep narrow-band images, K648 is afairly typical double-shelled elliptical, but with a bright arc at one end ofthe major axis that is especially prominent in [NII]; this feature is probablya collection of FLIERs. The nebula is surrounded by a faint, smooth ellipticalhalo, which appears undisturbed by any interaction with the interstellarmedium. Adopting Teff = 40,000 +- 3,000 K based upon published spectral-lineanalyses, and employing our new broad-band optical flux data along with theknown cluster distance, we find log L/L_sun = 3.78 +- 0.08 for the K648 centralstar. Theoretical post-asymptotic-giant-branch evolutionary tracks imply a massof 0.60 +- 0.02 M_sun for this luminosity, which is significantly higher thanthe mean mass of white dwarfs in globular clusters and the halo field (0.50 +-0.02). The K648 central star exhibits no significant photometric variability inour data; thus we find no direct evidence of a close binary companion. Wesuggest that the progenitor of K648 experienced mass augmentation in aclose-binary merger, allowing it to evolve to a remnant of higher mass thanthose of the single stars in the cluster.Comment: Accepted for publication in The Astronomical Journal (23 pages,  includes 3 figures, one color image

[ITAL]HUBBLE SPACE TELESCOPE[/ITAL][ITAL]Hubble Space Telescope[/ITAL] Observations of the Planetary Nebula K648 in the Globular Cluster M15