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Table 4

Magnetic spin-down timescales and ages.

Star Bp M R v τ spin Age(300) Age(100)
[kG] M R km s-1 [10-7M yr-1] [Myr] [Myr] [Myr]

HD 191612 2.5 37.7 12.3 2400 0.3 3.8
HD 148937 1.0 57.9 16.6 2600 0.3 11.3
HD 108 0.5–2 48.8 19.4 2000 1.0 2.0–7.8
Θ1 Ori C 1.1 23.8 6.5 2500 3.0 3.24
ζ Ori A 0.05–0.1 42.8 25.4 2100 17.0 6.5–13.0
HD 57682 1.7 22.0 7.0 1200 0.014 18.8
τ Sco 0.5 15.9 5.3 2000 0.3 17.0

Notes. The magnetic spin-down timescale is calculated according to Ud-Doula et al. (2009). Bp is the polar magnetic field. The stellar and wind parameters are used to calculate τspin. We have assumed a value of 0.1 for the moment of inertia constant k (see Eq. (25) of Ud-Doula et al. 2009). The entry “age(300)” is the age of the star estimated from the HR diagram built with evolutionary tracks computed for an initial rotational velocity of 300 km s-1. Similarly, “age(100)” is the age for V sin i = 100 km s-1.

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