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

High-dispersion spectroscopic observations are used to refine orbitalelements for the symbiotic binary CH Cyg. The current radial velocities, addedto a previously published 13 year time series of infrared velocities for the Mgiant in the CH Cyg symbiotic system, more than double the length of the timeseries to 29 years. The two previously identified velocity periods areconfirmed. The long period, revised to 15.6 +/- 0.1 yr, is shown to result froma binary orbit with a 0.7 solar mass white dwarf and 2 solar mass M giant. Masstransfer to the white dwarf is responsible for the symbiotic classification. CHCyg is the longest period S-type symbiotic known. Similarities with the longerperiod D-type systems are noted. The 2.1 year period is shown to be on Wood'ssequence D, which contains stars identified as having long secondary periods(LSP). The cause of the LSP variation in CH Cyg and other stars is unknown.  From our review of possible causes, we identify g-mode non-radial pulsationas the leading mechanism for LSP variation in CH Cyg. If g-mode pulsation isthe cause of the LSPs a radiative region is required near the photosphere ofpulsating AGB stars.

Infrared Spectroscopy of Symbiotic Stars. VII. Binary Orbit and Long Secondary Period Variability of CH Cygni