The CARMENES search for exoplanets around M dwarfs

High-resolution optical and near-infrared spectroscopy of 324 survey stars

¹ Institut für Astrophysik, Georg-August-Universität, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
² Centro de Astrobiología (CSIC-INTA), Instituto Nacional de Técnica Aeroespacial, Ctra. de Torrejón a Ajalvir, km 4, 28850 Torrejón de Ardoz, Madrid, Spain
³ Zentrum für Astronomie der Universtät Heidelberg, Landessternwarte, Königstuhl 12, 69117 Heidelberg, Germany
⁴ Institut de Ciències de l’Espai (CSIC-IEEC), Campus UAB, c/ de Can Magrans s/n, 08193 Bellaterra, Barcelona, Spain
⁵ Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁶ Centro Astronómico Hispano-Alemán (CSIC-MPG), Observatorio Astronómico de Calar Alto, Sierra de los Filabres, 04550 Gérgal, Almería, Spain
⁷ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁸ Departamento de Astrofísica y Ciencias de la Atmósfera, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁹ Instituto de Astrofśica de Canarias, Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain and Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹⁰ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
¹¹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
¹² Leiden Observatory, Leiden University, Postbus 9513, 2300 RA, Leiden, The Netherlands
¹³ Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
¹⁴ School of Physics and Astronomy, Queen Mary, University of London, 327 Mile End Road, London, E1 4NS
¹⁵ Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro 1, Sta. Ma. Tonantzintla, Puebla, Mexico
¹⁶ FRACTAL SLNE. C/ Tulipán 2, P13-1A, 28231 Las Rozas de Madrid, Spain
¹⁷ Institut für Theoretische Physik und Astrophysik, Leibnizstraße 15, 24118 Kiel, Germany
¹⁸ Osserv. Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
¹⁹ Dipartimento di Fisica, Unversità di Roma, “Tor Vergata”, via della Ricerca Scientifica, 1 – 00133 Roma, Italy
²⁰ Weizmann Institute of Science, 234 Herzl Street, Rehovot 761001, Israel
²¹ University College Dublin, School of Physics, Belfield, Dublin 4, Ireland
²² European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile
²³ The Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Ave, Chicago, IL 60637, USA
²⁴ Univ. Granada, Av. del Hospicio, s/n, 18010 Granada, Spain
²⁵ QUCAM Astronomical Detectors, http://www.qucam.com/
²⁶ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München
²⁷ Dpto. de Teoría de la Señal y Comunicaciones, Universidad Carlos III de Madrid, Escuela Politécnica Superior, Avda. de la Universidad, 30. 28911 Leganés, Madrid, Spain
²⁸ Dpto. de Física, Ingeniería de Sistemas y Teoría de la Señal, Escuela Politécnica Superior, Universidad de Alicante, Apdo.99, 03080, Alicante, Spain
²⁹ INAF, Osservatorio Astrofisico di Torino, via Osservatorio 20, 10025 Pino Torinese, Italy

^★ Corresponding author: A. Reiners, e-mail: Ansgar.Reiners@phys.uni-goettingen.de

Received: 6 October 2017
Accepted: 8 November 2017

Abstract

The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520–1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700–900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s⁻¹ in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3–4 m s⁻¹.