The CARMENES Search for Exoplanets Around M Dwarfs: A Homogeneous Catalogue of Projected Rotational Velocities with Limb-darkening Corrections

Researchers have published a new homogeneous catalogue of projected rotational velocities for M dwarf stars, incorporating limb-darkening effects to improve the precision of exoplanet detection measurements. The study, based on data from the CARMENES spectrograph, analyzes 392 M dwarf stars observed with the instrument’s high-resolution capabilities.

The CARMENES instrument is a dual-channel, high-resolution spectrograph with a resolution greater than 80,000 that has been highly successful in detecting exoplanets around M-dwarf stars using the radial-velocity technique. It also enables precise measurements of projected rotational velocity (vsini) from spectral line broadening, which is crucial for understanding stellar properties and correcting for activity effects in exoplanet studies.

The research team developed an oversampled convolution method that incorporates a realistic limb-darkening model to determine vsini from CARMENES spectra by comparing observed spectra with template stars. This approach was tested using high-resolution synthetic spectra covering effective temperatures from 2500 to 4000 K and projected rotational velocities up to 50 km/s.

Applied to the 392 M dwarfs in the CARMENES sample, the new method yields vsini measurements or upper limits (at 2 km/s) with a median relative uncertainty of 6.8%. This represents a substantial improvement over existing methods in the literature, which reported a median relative uncertainty of 15.4%.

The resulting catalogue provides the largest uniform set of vsini measurements for M dwarf stars to date. It includes significantly updated values for several previously observed targets and adds 36 new targets to the sample. Stellar rotation measurements are important because they are closely linked to both stellar age and magnetic activity, enabling age estimation through gyrochronology and helping trace the evolution of planetary systems.

Accurate rotation measurements are also essential for constraining and correcting stellar activity effects, which can interfere with exoplanet detection and characterization. By reducing uncertainty in vsini determinations, the new catalogue supports more robust analysis of exoplanetary systems around M dwarf stars, which are common targets in the search for potentially habitable worlds.

The study was conducted by an international team of researchers including R. Varas, G. Morello, M. Zechmeister, P. J. Amado, F. J. Pozuelos, J. A. Caballero, A. Claret, C. Cifuentes, R. Morales, A. Quirrenbach, A. Reiners, I. Ribas, V. J. S. Béjar, M. Cortés-Contreras, A. P. Hatzes, Th. Henning, I. Hermelo, H. L. Ruh, A. Schweitzer, H. M. Tabernero and M. R. Zapatero Osorio from institutions across Spain, Germany, Italy, and other countries.

The research was submitted to arXiv on April 16, 2026, and published in the astrophysics section under the title “The CARMENES search for exoplanets around M dwarfs. A homogeneous catalogue of projected rotational velocities accounting for limb-darkening.” The work contributes to ongoing efforts to improve the precision of stellar parameter measurements for exoplanet science.