The CARMENES search for exoplanets around M dwarfs

Magnesium and silicon abundances of K7–M5.5 stars

¹ 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
² Centro de Astrobiología, CSIC-INTA, Carretera de Ajalvir km 4, 28850 Torrejón de Ardoz, Madrid, Spain
³ Institut für Astrophysik und Geophysik, Georg-August-Universität-Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
⁴ Centre for Planetary Habitability, Department of Geosciences, University of Oslo, Sem Saelands vei 2b 0315 Oslo, Norway
⁵ Centro de Astrobiología, CSIC-INTA, Camino Bajo del Castillo s/n, 28691 Villanueva de la Cañada, Madrid, Spain
⁶ Universidad de La Laguna, Departamento de Astrofísica, 38206 La Laguna, Tenerife, Spain
⁷ Instituto de Astrofísica de Canarias, c/ Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
⁸ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
⁹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁰ Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
¹¹ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹² Institut de Ciències de l’Espai (CSIC), Campus UAB, c/ de Can Magrans s/n, 08193 Cerdanyola del Vallès, Spain
¹³ Institut d’Estudis Espacials de Catalunya (IEEC), c/ Gran Capità 2-4, 08034 Barcelona, Spain
¹⁴ Centro Astronómico Hispano-Alemán, Observatorio de Calar Alto, Sierra de los Filabres, 04550 Gérgal, Almería, Spain

Received: 21 March 2024
Accepted: 15 July 2024

Abstract

We present the abundances of magnesium (Mg) and silicon (Si) for 314 dwarf stars with spectral types in the interval K7.0–M5.5 (T_eff range ≈ 4200–3050 K) observed with the CARMENES high-resolution spectrograph at the 3.5 m telescope at the Calar Alto Observatory. Our analysis employs the BT-Settl model atmospheres, the radiative transfer code Turbospectrum, and a state-of-the-art selection of atomic and molecular data. These Mg and Si abundances are critical for understanding both the chemical evolution and assembly of the Milky Way and the formation and composition of rocky planets. Our chemical abundances show a line-to-line scatter at the level of 0.1 dex for all studied spectral types. The typical error bar of our chemical abundance measurements is ± 0.11 dex (Mg) and ± 0.16 dex (Si) for all spectral types based on the comparison of the results obtained for stellar components of multiple systems. The derived abundances are consistent with the galactic evolution trends and observed chemical abundance distribution of earlier FGK-type stars in the solar neighbourhood. Besides, our analysis provides compatible abundances for stars in multiple systems. In addition, we studied the abundances of different galactic stellar populations. In this paper, we also explore the relation of the Mg and Si abundances of stars with and without known planets.