摘要:Context. It is still unclear how common the Sun is when compared to
other similar stars in regards to some of its physical properties, such as rotation.
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.
Aims. 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.
Methods. We used high-resolution (R = 115 000) spectra
obtained with the HARPS spectrograph and the 3.6 m 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.
Results. Our sample of solar twins include some spectroscopic binaries
with enhanced rotational velocities, and we do not find any nonspectroscopic binaries with
unusually high rotation velocities. We verified that the Sun does not have a peculiar
rotation, but the solar twins exhibit rotational velocities that depart from the Skumanich
relation.
Conclusions. The Sun is a regular rotator when compared to solar twins
with a similar age. Additionally, we obtain a rotational braking law that better describes
the stars in our sample (v ∝
t-0.6) in contrast to previous,
often-used scalings.
关键词:Sun: rotation;stars: solar-type;stars: rotation;stars: fundamental parameters