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 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 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 O O O O O O O O O O O O O O O O O B-CelestialObject 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 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-Tag
tokens: different dependencies on the three stellar parameters. We chose the molecular TiO bands around and Å (- and - electronic transitions, respectively) since these oxide bands are very sensitive to effective temperature, but almost insensitive to surface gravity (Fig. 1 ). For cooler stars, as shown here, a dependence on surface gravity is introduced by the increasing micro-turbulent velocities, which enhance the line width towards lower values (see Wende et al. (2009) for FeH as an example). More sensitive to surface gravity are alkali lines (Fig. 1 ), which show large alterations of their line wings that are due to pressure broadening (in case of the K lines it is more pronounced towards cooler temperatures). We chose the K- and Na-line pairs at around Å and Å, respectively. To determine the metallicity, we can use all these regions as well because the -TiO band and the alkali lines are strongly dependent on this quantity (see Fig. 2 ). Rajpurohit et al. (2014) also used the K- and Na-line pairs because of their sensitivity to gravity and metallicity, as well as several TiO-bands for temperature determination. They also illustrated the dependency on the different stellar parameters. The chosen spectral regions are also affected by lines of the Earth’s atmosphere. Especially the K- and Na-line pairs are contaminated by O2 and H2O bands, respectively. We used masks to exclude the atmospheric lines from the fit. The contamination of the TiO bands around and Å is very weak and can be neglected. The degree of sensitivity on a certain parameter for a particular line (band) also varies. In Fig. 3 we show how the width of a -level in a -map changes with varying effective temperature (i.e. the of the synthetic spectrum from which the -map is produced is varied) for a fixed surface gravity of cgs and metallicity of cgs. The change is also measured in terms of discretion elements in the -maps, since this determines the given resolution (left axis). All investigated regions become less gravity sensitive towards higher , which is probably due to the increasing thermal broadening, which becomes stronger than the pressure broadening (see also Sect. 3.3 ). At this point we have to keep in mind that the sensitivity curves only represent the behaviour for the chosen parameter values. They look different for other metallicities or surface gravities, which are not shown in detail here. Nevertheless, it becomes clear that the combined -map of all regions is the best choice for most temperatures and provides the highest sensitivity. Even though the sensitivity of the K lines is better for most temperatures than the combined one, we would not suggest to use only these lines because the results would then only depend on two lines. Experience in fitting real observations showed that the results deduced from the K lines alone can differ from the combined solution where the latter matches the actual parameters to a higher accuracy. 3.2. <inline-formula