CARMENES input catalogue of M dwarfs

IX. Multiplicity from close spectroscopic binaries to ultra-wide systems

¹ Centro de Astrobiología, CSIC-INTA, Camino Bajo del Castillo s/n, Campus European Space Astronomy Centre, 28692 Villanueva de la Cañada, Madrid, Spain
² Departamento de Física de la Tierra y Astrofísica & IPARCOS-UCM (Instituto de Física de Partículas y del Cosmos de la UCM), Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
³ UNIE Universidad, Departamento de Ciencia y Tecnología, Arapiles 14, 28015 Madrid, Spain
⁴ Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁵ Instituto de Astrofísica de Canarias, Vía Láctea s/n, 38205 San Cristóbal de La Laguna, Tenerife, Spain
⁶ Departamento de Astrofísica, Universidad de La Laguna, Astrofísico Francisco Sánchez s/n, 38206 La Laguna, Tenerife, Spain
⁷ Department of Astronomy and Astrophysics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
⁸ Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
⁹ Institut für Astrophysik und Geophysik, Georg-August-Universität-Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
¹⁰ Institut de Ciències de l’Espai (CSIC-IEEC), Can Magrans s/n, Campus UAB, 08193 Bellaterra, Barcelona, Spain
¹¹ Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain

^★ Corresponding author; ccifuentes@cab.inta-csic.es

Received: 8 October 2024
Accepted: 28 November 2024

Abstract

Context. Multiplicity studies greatly benefit from focusing on M dwarfs because they are often paired in a variety of configurations with both stellar and substellar objects, including exoplanets.

Aims. We aim to address the observed multiplicity of M dwarfs by conducting a systematic analysis using the latest available astropho-tometric data.

Methods. For every star in a sample of 2214 M dwarfs from the CARMENES catalogue, we investigated the existence of resolved and unresolved physical companions in the literature and in all-sky surveys, especially in Gaia DR3 data products. We covered a very wide range of separations, from known spectroscopic binaries in tight arrangements (~0.01 au) to remarkably separated ultra-wide pairs (~10⁵ au).

Results. We identified 835 M dwarfs in 720 multiple systems, predominantly binaries. Thus, we propose 327 new binary candidates based on Gaia data. If these candidates are finally confirmed, we expect the multiplicity fraction of M dwarfs to be 40.3_−2.0^+2.1%. When only considering the systems already identified, the multiplicity fraction is reduced to 27.8_−1.8^+1.9%. This result is in line with most of the values published in the literature. We also identified M-dwarf multiple systems with FGK, white dwarf, ultra-cool dwarf, and exoplanet companions, as well as those in young stellar kinematic groups. We studied their physical separations, orbital periods, binding energies, and mass ratios.

Conclusions. We argue that based on reliable astrometric data and spectroscopic investigations from the literature (even when considering detection biases), the multiplicity fraction of M dwarfs could still be significantly underestimated. This calls for further high-resolution follow-up studies to validate these findings.