2015A&A...578A..33L


Query : 2015A&A...578A..33L

2015A&A...578A..33L - Astronomy and Astrophysics, volume 578A, 33-33 (2015/6-1)

Oxygen isotopic ratios in intermediate-mass red giants.

LEBZELTER T., STRANIERO O., HINKLE K.H., NOWOTNY W. and ARINGER B.

Abstract (from CDS):

The abundances of the three main isotopes of oxygen are altered in the course of the CNO-cycle. When the first dredge-up mixes the burning products to the surface, the nucleosynthesis processes can be probed by measuring oxygen isotopic ratios. By measuring 16O/17O and 16O/18O in red giants of known mass we compare the isotope ratios with predictions from stellar and galactic evolution modelling. Oxygen isotopic ratios were derived from the K-band spectra of six red giants. The sample red giants are open cluster members with known masses of between 1.8 and 4.5M. The abundance determination employs synthetic spectra calculated with the COMARCS code. The effect of uncertainties in the nuclear reaction rates, the mixing length, and of a change in the initial abundance of the oxygen isotopes was determined by a set of nucleosynthesis and mixing models using the FUNS code. The observed 16O/17O ratios are in good agreement with the model results, even if the measured values do not present clear evidence of a variation with the stellar mass. The observed 16O/18O ratios are clearly lower than the predictions from our reference model. Variations in nuclear reaction rates and mixing length parameter both have only a very weak effect on the predicted values. The 12C/13C ratios of the K giants studied implies the absence of extra-mixing in these objects. A comparison with galactic chemical evolution models indicates that the 16O/18O abundance ratio underwent a faster decrease than predicted. To explain the observed ratios, the most likely scenario is a higher initial 18O abundance combined with a lower initial 16O abundance. Comparing the measured 18O/17O ratio with the corresponding value for the interstellar medium points towards an initial enhancement of 17O as well. Limitations imposed by the observations prevent this from being a conclusive result.

Abstract Copyright:

Journal keyword(s): nuclear reactions, nucleosynthesis, abundances - stars: abundances - stars: evolution - stars: late-type

Simbad objects: 18

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Number of rows : 18
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 * bet And PM* 01 09 43.92388 +35 37 14.0075 5.58 3.62 2.05 0.81 -0.19 M0+IIIa 555 1
2 * alf Ari PM* 02 07 10.40570 +23 27 44.7032 4.29 3.17 2.01 1.15 0.54 K2-IIIbCa-1 621 2
3 HD 16068 * 02 36 52.7997095160 +55 54 55.443018600   9.18 7.45     K3II-III 35 0
4 Cl Trumpler 2 OpC 02 36 55.7 +55 54 18           ~ 110 0
5 NGC 1545 OpC 04 20 48.5 +50 13 16   7.2 6.2     ~ 108 0
6 HD 27292 * 04 20 57.5014421472 +50 15 17.412424956   8.77 7.13     K2+III 36 0
7 * 2 Aur * 04 52 37.9803457176 +36 42 11.477114460   6.164 4.779     K3-IIIBa0.4 143 0
8 HD 49050 * 06 45 44.1971561136 -21 03 43.968412980   9.26 7.85     K2/3(III) 24 0
9 M 41 OpC 06 45 59.8 -20 42 58   4.89 4.5     ~ 279 0
10 NGC 2548 OpC 08 13 38.9 -05 43 34           ~ 180 0
11 HD 68879 SB* 08 14 17.0315157888 -05 54 00.577990080   9.29 8.19     G9IIIK-2CH0.5 36 0
12 NAME Ursa Major Moving Group MGr 12 32 +57.0           ~ 433 2
13 * bet UMi V* 14 50 42.32580 +74 09 19.8142 5.32 3.55 2.08 0.97 0.21 K4-III 326 1
14 * alf Ser PM* 15 44 16.0743159 +06 25 32.263272 5.080 3.800 2.630 1.82 1.25 K2IIIbCN1 516 0
15 * bet Peg LP* 23 03 46.45746 +28 04 58.0336 6.05 4.09 2.42 0.92 -0.40 M2.5II-III 592 1
16 NGC 7789 415 SB* 23 57 03.2501165215 +56 45 57.912486452   12.55 10.6648   8.481 K5II 38 0
17 NGC 7789 OpC 23 57 20.2 +56 43 34   7.68 6.7     ~ 515 0
18 NGC 7789 971 RG* 23 57 51.5681710632 +56 38 56.654717784   12.94 11.0453   8.648 M3III 34 0

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2023.11.29-17:01:21

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