M dwarfs and the fraction of high carbon-to-oxygen stars in the solar neighbourhood

Abstract

We investigate the frequency of high carbon-to-oxygen (C/O $=0.9$) M dwarf stars in the solar neighbourhood. Using synthetic spectra, we find that such M dwarfs would have weaker TiO bands relative to hydride features. Similar weakening has already been detected in M-subdwarf (sdM) stars. By comparing to existing spectroscopic surveys of nearby stars, we show that less than one percent of nearby stars have high carbon-to-oxygen ratios. This limit does not include stars with C/O$=0.9$, [m/H]$>0.3$, and [C/Fe]$>0.1$, which we predict to have low-resolution optical spectra similar to solar metallicity M dwarfs.

MNRAS, accepted

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Cited by in corpus (4)

• The SPHINX M-dwarf Spectral Grid. I. Benchmarking New Model Atmospheres to Derive Fundamental M-Dwarf Properties
• The physical mechanism behind M dwarf metallicity indicators and the role of C and O abundances
• Wolf 1130: A Nearby Triple System Containing a Cool, Ultramassive White Dwarf
• Carbon-to-Oxygen Ratios in M dwarfs and Solar-type stars