2017MNRAS.470.2007W

New high-resolution spectroscopy and BVR photometry together with literature data on the complex massive quaternary star QZ Car are collected and analysed. Absolute parameters are found as follows. System A: M₁ = 43 (±3), M₂ = 19 (+3 -7), R₁ = 28 (±2), R₂ = 6 (±2), (☉); T₁ ∼ 28 000, T₂ ∼ 33 000 K; System B: M₁ = 30 (±3), M₂ = 20 (±3), R₁ = 10 (±0.5), R₂ = 20 (±1), (☉); T₁ ∼ 36 000, T₂ ∼ 30 000 K (model dependent temperatures). The wide system AB: Period = 49.5 (±1) yr, Epochs, conjunction = 1984.8 (±1), periastron = 2005.3 (±3) yr, mean separation = 65 (±3), (au); orbital inclination = 85 (+5 -15) deg, photometric distance ∼2700 (±300) pc, age = 4 (±1) Myr. Other new contributions concern: (a) analysis of the timing of minima differences (O - C)s for the eclipsing binary (System B); (b) the width of the eclipses, pointing to relatively large effects of radiation pressure;(c) inferences from the rotational widths of lines for both Systems A and B; and (d) implications for theoretical models of early-type stars. While feeling greater confidence on the quaternary's general parametrization, observational complications arising from strong wind interactions or other, unclear, causes still inhibit precision and call for continued multiwavelength observations. Our high-inclination value for the AB system helps to explain failures to resolve the wide binary in the previous years. The derived young age independently confirms membership of QZ Car to the open cluster Collinder 228.