The CARMENES search for exoplanets around M dwarfs

A homogeneous catalogue of projected rotational velocities accounting for limb darkening

¹ Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
² INAF – Palermo Astronomical Observatory, Piazza del Parlamento, 1, 90134 Palermo, Italy
³ Institut für Astrophysik und Geophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
⁴ Centro de Astrobiología, CSIC-INTA, Camino Bajo del Castillo s/n, Campus ESAC, 28692 Villanueva de la Cañada, Madrid, Spain
⁵ Universidad de Granada, c/ Gran Vía de Colón 48, 18010 Granada, Spain
⁶ Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
⁷ Institut de Ciències de l’Espai, CSIC, c/ de Can Magrans s/n, Campus UAB, 08193 Bellaterra, Barcelona, Spain
⁸ Institut d’Estudis Espacials de Catalunya, 08860 Castelldefels, Barcelona, Spain
⁹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹⁰ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹¹ Departamento de Física de la Tierra y Astrofísica & IPARCOS Instituto de Física de Partículas y del Cosmos, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, Plaza de Ciencias 1, 28400 Madrid, Spain
¹² Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
¹³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁴ Centro Astronómico Hispano en Andalucía, Observatorio Astronómico de Calar Alto, Sierra de los Filabres, 04550 Gérgal, Almería, Spain
¹⁵ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany

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Received: 28 January 2026
Accepted: 10 April 2026

Abstract

Stellar rotation is closely linked to both the age and the magnetic activity of stars. Through gyrochronology, studying stellar rotation provides a means to estimate stellar ages and trace the evolution of planetary systems, and it is also a crucial means to constrain and correct stellar activity effects for robust exoplanet detection and characterisation. CARMENES is a dual-channel, high-resolution (ℛ > 80 000) 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 (v sin i) from spectral line broadening. We present an oversampled convolution method that incorporates a realistic limb-darkening model to determine v sin i 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 spectrat that span effective temperatures of 2500–4000 K and projected rotational velocities of up to 50 km s⁻¹. We applied our method to 392 M dwarfs observed with CARMENES and it yielded v sin i measurements (or upper limits at 2 km s⁻¹) with a median relative uncertainty of 6.8%, which is substantially smaller than the 15.4% reported in the literature. This work provides the largest uniform catalogue of v sin i measurements for M dwarfs, including significantly updated values for several targets, along with 36 new targets.