1998AJ....115.1617C

We analyze new photometric data for the Herbig Be eclipsing binary TY CrA, which securely reveal the secondary eclipse, ∼0.03 mag deep in y. From the light-curve solution and our previous spectroscopic data, absolute dimensions of the primary and secondary stars are derived. The masses are found to be M₁ = 3.16±0.02 M_☉ and M₂ = 1.64 ±0.01 M_☉, the radii are R₁ = 1.80±0.10 R_☉ and R₂ = 2.08±0.14 R_☉, the luminosities are L₁ = 67±12 L_☉ and L₂ = 2.4±0.8 L_☉, and the effective temperatures are T₁ = 12,000±500 K and T₂ = 4900 ±400 K. Here the uncertainties represent high-confidence limits, not standard deviations. The secondary star is a pre-main-sequence star located at the base of the Hayashi tracks. As such, it is the least evolved star with a dynamically measured mass. Given higher effective temperatures for the primary (e.g., 12,500 K), the solar-composition 1.64 M_☉ evolutionary tracks of Swenson et al., Claret, and D'Antona & Mazzitelli are all consistent with the properties of the TY CrA secondary and suggest an age of order 3 Myr. The radius and projected rotational velocity of the secondary star are consistent with synchronous rotation. The primary star is located near the zero-age main sequence, which, for solar compositions, is consistent with an age of 3 Myr. However, the primary star is not well represented by any of the 3.16 M_☉ evolutionary models, which predict somewhat higher effective temperatures than observed.