2019ApJ...878...43M -
Astrophys. J., 878, 43-43 (2019/June-2)
Carbon isotope ratios in M10 giants.
MAAS Z.G., GERBER J.M., DEIBEL A. and PILACHOWSKI C.A.
Abstract (from CDS):
We measured carbon abundances and the 12C/13C ratio in 31 giant branch stars with previous CN and CH band measurements that span -2.33 < MV < 0.18 in the globular cluster M10 (NGC 6254). Abundances were determined by comparing CO features at ∼2.3 µm and specifically the 13CO bandhead at 2.37 µm, to synthetic spectra generated with MOOG. The observed spectra were obtained with GNIRS on Gemini North with a resolution of R ≃ 3500. The carbon abundances derived from the IR spectra agree with previous [C/Fe] measurements found using CN and CH features at the near-UV/blue wavelength range. We found an average carbon isotope ratio of 12C/13C = 5.10–0.17+0.18 for first generation stars (CN-normal; 13 stars total) and 12C/13C = 4.84–0.22+0.27 for second generation stars (CN-enhanced; 15 stars). We therefore find no statistically significant difference in 12C/13C ratio between stars in either population for the observed magnitude range. Finally, we created models of the expected carbon, nitrogen, and 12C/13C surface abundance evolution on the red giant branch due to thermohaline mixing using the MESA stellar evolution code. The efficiency of the thermohaline mixing must be increased to a factor of ≃60 to match [C/Fe] abundances, and by a factor of ≃666 to match 12C/13C ratios. We could not simultaneously fit the evolution of both carbon and the 12C/13C ratio with models using the same thermohaline efficiency parameter.
Abstract Copyright:
© 2019. The American Astronomical Society. All rights reserved.
Journal keyword(s):
globular clusters: individual: M10 - stars: abundances - stars: evolution
Simbad objects:
42
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