SIMBAD references

We discuss the influence of rotation on the combined synthesis of ⁴⁴Ti and ⁵⁶Ni in massive stars. While ⁵⁶Ni is significantly produced by both complete and incomplete explosive Si burning, ⁴⁴Ti is mainly produced by complete explosive Si burning, with a minor contribution (in standard non-rotating models) from incomplete explosive Si burning and O burning (both explosive and hydrostatic). We find that, in most cases, the thickness of the region exposed to incomplete explosive Si burning increases in rotating models (initial velocity, v_ini = 300 km s^–1) and since ⁵⁶Ni is significantly produced in this zone, the fraction of mass coming from the complete explosive Si burning zone necessary to get the required amount of ⁵⁶Ni reduces. Therefore the amount of ⁴⁴Ti ejected for a given fixed amount of ⁵⁶Ni decreases in rotating models. However, some rotating models at [Fe/H] = -1 develop a very extended O convective shell in which a consistent amount of ⁴⁴Ti is formed, preserved, and ejected in the interstellar medium. Hence a better modeling of the thermal instabilities (convection) in the advanced burning phases together with a critical analysis of the cross sections of the nuclear reactions operating in O burning are relevant for the understanding of the synthesis of ⁴⁴Ti.