YaPSI: a new database of evolutionary tracks and isochrones

The Yale-Potsdam Stellar Isochrones (YaPSI) cover the low and intermediate stellar mass regime (0.15 to 5.0 M_⊙) for a wide range of solar-scaled chemical compositions (metallicity from -0.5 to +0.3; helium mass fraction from 0.25 to 0.37, assigned independently of each other). The tracks are finely spaced in mass, to allow for accurate interpolation. The models feature state-of-the-art input physics relevant to low-mass stars modeling (surface boundary conditions, equation of state), thus updating the faint end of the Yonsei-Yale (YY) isochrones. Utility codes, such as an isochrone interpolator in age, metallicity and helium content, are also provided. The YaPSI isochrones are in good agreement with the empirical mass-luminosity and mass-radius relations available to date, and provide satisfactory fitting of the color-magnitude diagrams of well-studied open clusters.