The CARMENES search for exoplanets around M dwarfs

Abstract

Context. The CARMENES instrument, installed at the 3.5 m telescope of the Calar Alto Observatory in Almería, Spain, was conceived to deliver high-accuracy radial velocity (RV) measurements with long-term stability to search for temperate rocky planets around a sample of nearby cool stars. Moreover, the broad wavelength coverage was designed to provide a range of stellar activity indicators to assess the nature of potential RV signals and to provide valuable spectral information to help characterise the stellar targets. Aims. We describe the CARMENES guaranteed time observations (GTO), spanning from 2016 to 2020, during which 19 633 spectra for a sample of 362 targets were collected. We present the CARMENES Data Release 1 (DR1), which makes public all observations obtained during the GTO of the CARMENES survey. Methods. The CARMENES survey target selection was aimed at minimising biases, and about 70% of all known M dwarfs within 10 pc and accessible from Calar Alto were included. The data were pipeline-processed, and high-level data products, including 18 642 precise RVs for 345 targets, were derived. Time series data of spectroscopic activity indicators were also obtained. Results. We discuss the characteristics of the CARMENES data, the statistical properties of the stellar sample, and the spectroscopic measurements. We show examples of the use of CARMENES data and provide a contextual view of the exoplanet population revealed by the survey, including 33 new planets, 17 re-analysed planets, and 26 confirmed planets from transiting candidate follow-up. A subsample of 238 targets was used to derive updated planet occurrence rates, yielding an overall average of 1.44 ± 0.20 planets with 1 M⊕ < Mpl sin i < 1000 M⊕ and 1 day < Porb < 1000 days per star, and indicating that nearly every M dwarf hosts at least one planet. All the DR1 raw data, pipeline-processed data, and high-level data products are publicly available online. Conclusions. CARMENES data have proven very useful for identifying and measuring planetary companions. They are also suitable for a variety of additional applications, such as the determination of stellar fundamental and atmospheric properties, the characterisation of stellar activity, and the study of exoplanet atmospheres.

The CARMENES search for exoplanets around M dwarfs

“…8. M-dwarf (T eff < 4000 K) planetary systems with at least one detected planet in the conservative sample of potentially habitable exoplanets (i.e., 0.5 M dwarfs, this value lies between ∼0.56-1.75 planets per star (Ribas et al 2023;Hardegree-Ullman et al 2019). Regarding the proximity of these systems, Dressing & Charbonneau (2015) estimated that the nearest nontransiting HZ planet could be 2.6 ± 0.4 pc away, and is within 3.5 pc with 95% confidence for potentially habitable 1-1.…”

ExoGemS Detection of a Metal Hydride in an Exoplanet Atmosphere at High Spectral Resolution

“…We created model CrH transmission spectra templates using the TRIDENT radiative transfer code (MacDonald & Lewis 2022), which employs the CrH line list from Burrows et al (2002). Since this is an old line list, we validated it by cross-correlating our template with a high-resolution, optical spectrum of a very low-mass, cold star (Teegarden's Star, M8) from CARMENES DR1 (Ribas et al 2023). Very low-mass stars and warmer brown dwarfs exhibit CrH absorption starting at 860 nm (e.g., Kirkpatrick et al 1999).…”

A Wolf 359 in Sheep's Clothing: Hunting for Substellar Companions in the Fifth-closest System Using Combined High-contrast Imaging and Radial Velocity Analysis

“…The RV instruments and measurements used in our analysis of Wolf 359 are summarized in Table 4 and available in full in machinereadable format online. The CARMENES data were retrieved from the DR1 release, which spans from 2016 to 2020 (Ribas et al 2023). The MAROON-X, HIRES, and HARPS data were provided directly by the observing teams.…”

“…The heritage of detecting exoplanets via the direct imaging technique has been to conduct blind surveys of hundreds of young star systems in search of a rare set of large gas giant planets on long-period orbits that are bright enough to detect using short integration times. Thanks to the growing abundance of long-baseline exoplanet RV data (e.g., Trifonov et al 2020;Rosenthal et al 2021;Ribas et al 2023), we can now use RV data in tandem with HCI observations to tailor our imaging observations to conduct lengthier measurements around fewer systems. Information from RV data can be applied to select viable targets for imaging, choose the optimal imaging filters, predict how much integration time is required, and predict when a companion will be at its maximum separation from its host star.…”