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

The Hipparcos Intermediate Astrometric Data for carbon stars have beenreprocessed using an algorithm which provides an objective criterion forrejecting anomalous data points and constrains the parallax to be positive. Newparallax solutions have been derived for 317 cool carbon stars, mostly of typesR and N. In this paper we discuss the results for the R stars. The mostimportant result is that the early R stars (i.e., R0 - R3) have absolutemagnitudes and V-K colors locating them among red clump giants in theHertzsprung-Russell diagram. Stars with subtypes R4 - R9 tend to be cooler andhave similar luminosity to the N-type carbon stars, as confirmed by theirposition in the (J-H, H-K) color-color diagram. The sample of early R-typestars selected from the Hipparcos Catalogue appears to be approximatelycomplete to magnitude K_0 ~ 7, translating into a completeness distance of 600pc if all R stars had M_K= -2 (400 pc if M_K= -1). With about 30 early R-typestars in that volume, they comprise about 0.04% (0.14% for M_K= -1) of the redclump stars in the solar neighborhood. Identification with the red clumplocates these stars at the helium core burning stage of stellar evolution,while the N stars are on the asymptotic giant branch, where helium shellburning occurs. The present analysis suggests that for a small fraction of thehelium core burning stars (far lower than the fraction of helium shell-burningstars), carbon produced in the interior is mixed to the atmosphere insufficient quantities to form a carbon star.Comment: 11 pages, 6 figures, A&A Latex. To appear in A&

Reprocessing theHipparcosdata for evolved giant stars II. Absolute magnitudes for the R-type carbon stars