  This is the fourth paper of our new release of the BaSTI (a Bag of Stellar
Tracks and Isochrones) stellar model and isochrone library. Following the
updated solar-scaled, alpha-enhanced, and white dwarf model libraries, we
present here alpha-depleted ([alpha/Fe] = -0.2) evolutionary tracks and
isochrones, suitable to study the alpha-depleted stars discovered in Local
Group dwarf galaxies and in the Milky Way. These calculations include all
improvements and updates of the solar-scaled and alpha-enhanced models, and
span a mass range between 0.1 and 15 Msun, 21 metallicities between [Fe/H] =
-3.20 and +0.45 with a helium-to-metal enrichment ratio dY/dZ = 1.31,
homogeneous with the solar-scaled and alpha-enhanced models. The isochrones --
available in several photometric filters -- cover an age range between 20 Myr
and 14.5 Gyr, including the pre-main-sequence phase. We have compared our
isochrones with independent calculations of alpha-depleted stellar models,
available for the same alpha-element depletion adopted in present
investigation. We have also discussed the effect of an alpha-depleted heavy
element distribution on the bolometric corrections in different wavelength
regimes. Our alpha-depleted evolutionary tracks and isochrones are publicly
available at the BaSTI website.
