ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O B-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O B-Wavelength O B-Wavelength O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O B-Wavelength O B-Wavelength O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O B-Wavelength O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O B-Dataset I-Dataset I-Dataset I-Dataset B-Citation I-Citation O O O O O O O O O O O O O O O O O O O O O O O O
tokens: which the excitation temperature can be found naturally depends on the number of usable lines. Typically, the excitation temperature could be constrained to better than ±150 K. Fortunately, the isotopic ratio is not highly sensitive to the excitation temperature, and uncertainties in the ±150 range have only a small effect on the resulting isotopic ratios. To reduce the uncertainty in the abundances in the case of ill-defined excitation temperatures, we investigated the relation between the excitation temperature, T exc , and the effective temperature, T eff . There is considerable basis for assuming that these quantities are related via the atmospheric structure and elemental abundances. Effective temperature is a measure of the total energy integrated over all wavelengths radiated from a unit of stellar surface area. The value is fixed by luminosity and radius and is an observable quantity. T eff is given by the relationwhere F is the bolometric flux received at Earth, σ is the Stefan–Boltzmann constant, and φ is the angular diameter (Ridgway et al. 1980 ). Most values of T eff for cool giants have been set using Equation ( 1 ) with φ determined by lunar occultations and interferometry (see, e.g., Ridgway et al. 1980 ; Richichi et al. 1999 ) and F determined from near-IR photometry. Observational limits associated with the techniques restrict the sample of objects in magnitude, diameter, and position on the sky. A second approach based on infrared flux (Blackwell Shallis 1977 ; Blackwell et al. 1990 ) also produces effective temperatures. Both techniques produce similar results. We limit our discussion to the angular diameter approach. Effective temperature is known to vary with spectral type, for the M giants nearly linearly (Richichi et al. 1999 ). Worthey Lee ( 2011 ) present a comparison of T eff versus V – K relations for cool giants. The Bessell et al. ( 1998 ) T eff versus V – K relation, derived from a compilation of occultation and interferometry diameters, is the best fit to the Worthey Lee ( 2011 ) data. Sharma et al. ( 2016 ) review a number of fits to the T eff versus M giant spectral type relation against several groups of synthetic spectra. A T eff –( V – K ) relation derived from a homogeneous set of angular diameters by Richichi et al. ( 1999 ) gives the best match and extends to the coolest non-Mira M giants. Therefore, we adopted the spectral type—effective temperature relation by Richichi et al. ( 1999 ) for our study. However, use of the Bessell et al. ( 1998 ) calibration would result in negligible change. All the calibrations show scatter around a mean relation. The Richichi et al. ( 1999 ) relation shows considerable scatter to lower temperatures. Since the sample stars are bright—in fact most (Table 1 ) are in the Yale Bright Star Catalog (Hoffleit 1964 )—there are well-determined spectral types and magnitudes. We ignore the galactic reddening of these nearby objects. Table 2 lists the parameters for the program