The Solar Twin Planet Search. IV.

Considering that gyrochronology relations are widely used today to estimate ages of stars in the main sequence, and that the Sun is used to calibrate it, it is crucial to assess whether these procedures are acceptable. We analyze the rotational velocities, limited by the unknown rotation axis inclination angle, of an unprecedented large sample of solar twins to study the rotational evolution of Sun-like stars, and assess whether the Sun is a typical rotator.

We used high-resolution (R=115000) spectra obtained with the HARPS spectrograph and the 3.6m telescope at La Silla Observatory. The projected rotational velocities for 81 solar twins were estimated by line profile fitting with synthetic spectra. Macroturbulence velocities were inferred from a prescription that accurately reflects their dependence with effective temperature and luminosity of the stars.