2006MNRAS.369..673B

Detailed evolutionary tracks and basic stellar parameters for the nearby subgiants 104 Tau and HD 168443 are presented and discussed. Both serve as invaluable key stars for accurate age-datings, especially as they possess the chemical signatures intermediate to the stars of the thick- and thin-disc population. We derive τ = 9.7^–0.6_+0.8Gyr for 104 Tau and τ = 9.8^–0.8_+1.0Gyr for HD 168443, very much in line with their local sibling HR 7569 at τ = 9.1±1.0 Gyr that was formerly presented in Bernkopf, Fiedler & Fuhrmann. Both, 104 Tau and HD 168443, thus add to our local sample of the rare but very relevant subgiants for the disc formation time-scales and support the notion of a thick disc as an extremely old τ ≥ 12 Gyr single-burst population, and a thin disc that has a local age of τ ∼ 8 Gyr.