CARMENES M dwarfs projected rotational velocities

Through gyrochronology, it provides a means to estimate stellar ages and trace the evolution of planetary systems, and it is also crucial to constrain and correct stellar activity effects for robust exoplanet detection and characterisation. CARMENES is a dual-channel, high-resolution (R>80000) spectrograph that has been highly successful in detecting exoplanets around M-dwarf stars using the radial-velocity technique, and it also enables precise measurements of the projected rotational velocity (vsini) from spectral line broadening.

We present an oversampled convolution method incorporating a realistic limb-darkening model to determine vsini from CARMENES spectra by comparing observed spectra with that of a template star. The advantages over existing methods in the literature have been assessed using high-resolution synthetic spectra spanning effective temperatures of 2500-4000K and projected rotational velocities of up to 50km/s. Applied to 392 M dwarfs observed with CARMENES, our method yields vsini measurements (or upper limits at 2km/s) with a median relative uncertainty of 6.8%, substantially smaller than the 15.4% reported in the literature.