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

We have carried out a detailed observational study of the light, color, andvelocity variations of two bright, carbon-rich proto-planetary nebulae, IRAS22223+4327 and 22272+5435. The light curves are based upon our observationsfrom 1994 to 2011, together with published data by Arkhipova and collaborators.They each display four significant periods, with primary periods for IRAS22223+4327 and 22272+5435 being 90 and 132 days, respectively. For each ofthem, the ratio of secondary to primary period is 0.95, a value much differentfrom that found in Cepheids, but which may be characteristic of post-AGB stars.Fewer significant periods are found in the smaller radial velocity data sets,but they agree with those of the light curves. The color curves generally mimicthe light curves, with the objects reddest when faintest. A comparison inseasons when there exist contemporaneous light, color, and velocity curvesreveals that the light and color curves are in phase, while the radial velocitycurves are 0.25 out of phase with the light curves. Thus they differ from whatis seen in Cepheids, in which the radial velocity curve is 0.50 P out of phasewith the light curve. Comparison of the observed periods and amplitudes withthose of post-AGB pulsation models shows poor agreement, especially for theperiods, which are much longer than predicted. These observational data,particularly the contemporaneous light, color, and velocity curves, provide anexcellent benchmark for new pulsation models of cool stars in the post-AGB,proto-planetary nebula phase.

Studies of Variability in Proto-Planetary Nebulae: II. Light and Velocity Curve Analyses of Iras 22272+5435 and 22223+4327