Influence of α-enhancement on effective temperatures of hot subdwarfs

Observations of metal elements in some halo or bulge globular clusters and in some elliptical galaxies have shown the alpha-enhancement phenomenon. Hot subdwarfs are important stars, e.g., they are important sources of far-ultraviolet light in the Galaxy and have successfully been used to explain the UV-upturn in elliptical galaxies. Therefore, we try to study the impacts of alpha-enhancement on hot subdwarfs. In our calculation, the value of the metallicity is 0.02, all the core masses of hot subdwarfs are 0.475 M (aS (TM)), and the envelope masses of the hot subdwarfs are 0.001, 0.005 and 0.016 M (aS (TM)), respectively. We find that the influences of alpha-enhancement on luminosity and evolutionary age of hot subdwarfs are not visible. But alpha-enhancement can make the effective temperatures of hot subdwarfs become higher, and the thicker their envelopes are, the more obvious this influence is.