Please use this identifier to cite or link to this item:
http://hdl.handle.net/20.500.12386/24877
Title: | The extent of mixing in stellar interiors: the open clusters Collinder 261 and Melotte 66 | Authors: | Drazdauskas, Arnas Tautvaišienė, Gražina RANDICH, Maria Sofia BRAGAGLIA, Angela Mikolaitis, Šarūnas Janulis, Rimvydas |
Issue Date: | 2016 | Journal: | ASTRONOMY & ASTROPHYSICS | Number: | 589 | First Page: | A50 | Abstract: | Context. Determining carbon and nitrogen abundances in red giants provides useful diagnostics to test mixing processes in stellar atmospheres. Aims: Our main aim is to determine carbon-to-nitrogen and carbon isotope ratios for evolved giants in the open clusters Collinder 261 and Melotte 66 and to compare the results with predictions of theoretical models. Methods: High-resolution spectra were analysed using a differential model atmosphere method. Abundances of carbon were derived using the C2Swan (0, 1) band head at 5635.5 Å. The wavelength interval 7940-8130 Å, which contains CN features, was analysed to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 Å. <BR /> Results: The mean values of the elemental abundances in Collinder 261, as determined from seven stars, are: [ C/Fe ] = -0.23 ± 0.02 (s.d.), [ N/Fe ] = 0.18 ± 0.09, [ O/Fe ] = -0.03 ± 0.07. The mean <SUP>12</SUP>C /<SUP>13</SUP>C ratio is 11 ± 2, considering four red clump stars and 18 for one star above the clump. The mean C/N ratios are 1.60 ± 0.30 and 1.74, respectively. For the five stars in Melotte 66 we obtained: [ C/Fe ] = -0.21 ± 0.07 (s.d.), [ N/Fe ] = 0.17 ± 0.07, [ O/Fe ] = 0.16 ± 0.04. The <SUP>12</SUP>C /<SUP>13</SUP>C and C/N ratios are 8 ± 2 and 1.67 ± 0.21, respectively. Conclusions: The <SUP>12</SUP>C /<SUP>13</SUP>C and C/N ratios of stars in the investigated open clusters were compared with the ratios predicted by stellar evolution models. The mean values of <SUP>12</SUP>C /<SUP>13</SUP>C ratios in Collinder 261 and Melotte 66 agree well with models of thermohaline-induced extra-mixing for the corresponding stellar turn-off masses of about 1.1-1.2 M<SUB>☉</SUB>. The mean C/N ratios are not decreased as much as predicted by the model in which the thermohaline- and rotation-induced extra-mixing act together. Based on observations collected at ESO telescopes under Guaranteed Time Observation programmes 071.D-0065, 072.D-0019, and 076.D-0220. | URI: | http://hdl.handle.net/20.500.12386/24877 | URL: | https://www.aanda.org/articles/aa/abs/2016/05/aa28138-16/aa28138-16.html | ISSN: | 0004-6361 | DOI: | 10.1051/0004-6361/201628138 | Bibcode ADS: | 2016A&A...589A..50D | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
aa28138-16.pdf | PDF editoriale | 828.58 kB | Adobe PDF | View/Open |
Page view(s)
73
checked on Sep 12, 2024
Download(s)
17
checked on Sep 12, 2024
Google ScholarTM
Check
Altmetric
Altmetric
Items in DSpace are published in Open Access, unless otherwise indicated.