On the rotational behaviour of parent stars of extrasolar planets

We analysed the behaviour of the rotational velocity in the parent stars of extrasolar planets. Projected rotational velocity v sin i and angular momentum were combined with stellar and planetary parameters, for a unique sample of 147 stars, amounting to 184 extrasolar planets, including 25 multiple systems. Indeed, for the present working sample we considered only stars with planets detected by the radial-velocity procedure. Our analysis shows that the v sin i distribution of stars with planets along the HR diagram follows the well-established scenario for the rotation of intermediate to low main-sequence stars, with a sudden decline in rotation near 1.2 M-circle dot. The decline occurs around T-eff similar to 6000 K, corresponding to the late-F spectral region. A statistical comparison of the distribution of the rotation of stars with planets and a sample of stars without planets indicates that the v sin i distribution for these two families of stars is drawn from the same population distribution function. We also found that the angular momentum of extrasolar planet parent stars follows, at least qualitatively, Kraft's relation J proportional to (M/M-circle dot)alpha. The stars without detected planets show a clear trend of angular momentum deficit compared to the stars with planets, in particular for masses higher than about 1.25 M-circle dot. Stars with the largest mass planets tend to have angular momentum comparable to or higher than the Sun.