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/

Zendy Plus

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

Zendy Tools

Zendy Open

CIT 6 is a carbon star in the transitional phase from the asymptotic giantbranch (AGB) to the protoplanetary nebulae (pPN). Observational evidences oftwo point sources in the optical, circumstellar arc segments in an HC$_3$N lineemission, and a bipolar nebula in near-infrared provide strong support for thepresence of a binary companion. Hence, CIT 6 is very attractive for studyingthe role of companions in the AGB-pPN transition. We have carried out highresolution $^{12}$CO $J=2-1$ and $^{13}$CO $J=2-1$ observations of CIT 6 withthe Submillimeter Array combined with the Submillimeter Telescope (single-dish)data. The $^{12}$CO channel maps reveal a spiral-shell pattern connecting theHC$_3$N segments in a continuous form, and an asymmetric outflow correspondingto the near-infrared bipolar nebula. Rotation of the $^{12}$CO channel peakposition may be related to the inner spiral winding and/or the bipolar outflow.An eccentric orbit binary is suggested for the presences of an anisotropic massloss to the west and a double spiral pattern. The lack of interarm emission tothe west may indicate a feature corresponding to the periastron passage of ahighly eccentric orbit of the binary. Spatially-averaged radial and spectralprofiles of $^{12}$CO $J=2-1$ and $^{13}$CO $J=2-1$ are compared with simplespherical radiative transfer models, suggesting a change of $^{12}$CO/$^{13}$COabundance ratio from $\sim30$ to $\sim50$ inward in the CSE of CIT 6. Themillimeter continuum emission is decomposed into extended dust thermal emission(spectral index $\sim-2.4$) and compact emission from radio photosphere(spectral index $\sim-2.0$).

High-resolution CO observation of the carbon star CIT 6 revealing the spiral structure and a nascent bipolar outflow