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

Context. Investigations of abundances of carbon and nitrogen in theatmospheres of evolved stars of open clusters may provide comprehensiveinformation on chemical composition changes caused by stellar evolution. Aims.Our main aim is to increase the number of open clusters with determinedcarbon-to nitrogen and carbon isotope ratios. Methods. High-resolution spectrawere analysed using a differential model atmosphere method. Abundances ofcarbon were derived using the C_2 Swan (0,1) band head at 5635.5 {\AA} (FEROSspectra) and the C_2 Swan (1,0) band head at 4737 {\AA} (UVES spectra). Thewavelength interval 7980-8130 {\AA}, with strong CN features was analysed todetermine nitrogen abundances and 12^C/13^C isotope ratios. The oxygenabundances were determined from the [Oi] line at 6300 {\AA}. Results. Theaverage value of 12^C/13^C isotope ratios of Cr 261 is equal to 18 \pm 2 infour giants and to 12 \pm 1 in two clump stars; it is equal to 16 \pm 1 in fourclump stars of the open cluster NGC 6253. The mean C/N ratios in Cr 261 and NGC6253 are equal to 1.67 \pm 0.06 and 1.37 \pm 0.09, respectively. Conclusions.The 12^C/13^C and C/N values in Cr 261 and NGC 6253 within limits ofuncertainties agree with the theoretical model of thermohaline-induced mixingas well as with the cool-bottom processing model

C, N, O abundances and carbon isotope ratios in evolved stars of the open clusters Collinder 261 and NGC 6253