HR diagram with evolutionary tracks computed with MESA for single-star models with masses corresponding to the components of δ Cir. The tracks begin at the zero-age main sequence (ZAMS) and end at core collapse. The dotted lines denote the ZAMS and the terminal-age main sequence (TAMS) for single, non-rotating stars without stellar wind mass loss (Paxton et al. 2015). Stellar winds and rotation are included in our models. The observed positions of all three stars are shown as dots with error bars. The primary has evolved away from the ZAMS, while the secondary and the tertiary remain close to it. Markers indicate when hydrogen and helium are exhausted, and the adjacent labels show the corresponding ages and masses.