A grid of ATLAS9 model atmospheres has been computed , spanning 3500 ~ { } { K } \leq T _ { eff } \leq 8000 ~ { } K , 0.0 \leq \log g \leq 5.0 , -4.0 \leq \mathrm { [ M / H ] } \leq 0.0 , and -0.8 \leq { [ \alpha / Fe ] } \leq + 1.2 .
These parameters are appropriate for stars in the red giant branch , subgiant branch , and the lower main sequence .
The main difference from a previous , similar grid ( 3 ) is the range of [ \alpha /Fe ] values .
A grid of synthetic spectra , calculated from the model atmospheres , is also presented .
The fluxes are computed every 0.02 Å from 6300 Å to 9100 Å .
The microturbulent velocity is given by a relation to the surface gravity .
This relation is appropriate for red giants , but not for subgiants or dwarfs .
Therefore , caution is urged for the synthetic spectra with \log g > 3.5 or for any star that is not a red giant .
Both the model atmosphere and synthetic spectrum grids are available online through VizieR .
Applications of these grids include abundance analysis for large samples of stellar spectra and constructing composite spectra for stellar populations .