Howarth, I; van Leeuwen, F; (2019) The distance, rotation, and physical parameters of ζ Pup. Monthly Notices of the Royal Astronomical Society 10.1093/mnras/stz291. (In press).

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Abstract

We scrutinize the Hipparcos parallax for the bright O supergiant ζ Pup, and confirm that the implied distance of 332 ± 11 pc appears to be reliable. We then review the implications for the star’s physical parameters, and the consequences for the interpretation of Pphot, the 1.78-d photometric period. The equatorial rotation period is <3.7 d (with 95% confidence), ruling out a proposed ∼5.1-d value. If the photometric period is the rotation period then i, the inclination of the rotation axis to the line of sight, is 33.⁰2 ± 1.⁰8. The inferred mass, radius, and luminosity are securely established to be less than canonical values for the spectral type, and are not in agreement with single-star evolution models. The runaway status, rapid rotation, and anomalous physical properties are all indicative of an evolutionary history involving binary (or multiple-star) interaction. We perform simple starspot modelling to show that the low axial inclination required if Prot = 1.78 d has testable spectroscopic consequences, which have not been identified in existing time series. If Pphot is directly related to drivers of systematic, high-velocity stellar-wind variability (‘discrete absorption components’) in ζ Pup, antisolar differential rotation is required. Model line profiles calculated on that basis are at variance with observations.

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