We present λ/Δλ=550-1200 near-infrared H and K spectra for a magnitude-limited sample of 79 asymptotic giant branch and cool supergiant stars in the central ~5 pc (diameter) of the Galaxy. We use a set of similar spectra obtained for solar neighborhood stars with known Teffand Mbolthat is in the same range as the Galactic center (GC) sample to derive Teffand Mbolfor the GC sample. We then construct the H-R diagram for the GC sample. Using an automated maximum likelihood routine, we derive a coarse star formation history of the GC. We find that (1) roughly 75% of the stars formed in the central few parsecs are older than 5 Gyr; (2) the star formation rate (SFR) is variable over time, with a roughly 4 times higher SFR in the last 100 Myr compared to the average SFR; (3) our model can match dynamical limits on the total mass of stars formed only by limiting the initial mass function to masses above 0.7 M☉(this could be a signature of mass segregation or of the bias toward massive star formation from the unique star formation conditions in the GC); (4) blue supergiants account for 12% of the total sample observed, and the ratio of red to blue supergiants is roughly 1.5; and (5) models with isochrones with [Fe/H]=0.0 over all ages fit the stars in our H-R diagram better than models with lower [Fe/H] in the oldest age bins, consistent with the finding of Ramírez et al. that stars with ages between 10 Myr and 1 Gyr have solar [Fe/H].
Galaxy: Center - Stars: AGB and Post-AGB - Stars: Late-Type - Stars: Supergiants