The CARMENES search for exoplanets around M dwarfs

Abstract

Light from celestial objects interacts with the molecules of the Earth’s atmosphere, resulting in the production of telluric absorption lines in ground-based spectral data. Correcting for these lines, which strongly affect red and infrared wavelengths, is often needed in a wide variety of scientific applications. Here, we present the template division telluric modeling (TDTM) technique, a method for accurately removing telluric absorption lines in stars that exhibit numerous intrinsic features. Based on the Earth’s barycentric motion throughout the year, our approach is suited for disentangling telluric and stellar spectral components. By fitting a synthetic transmission model, telluric-free spectra are derived. We demonstrate the performance of the TDTM technique in correcting telluric contamination using a high-resolution optical spectral time series of the feature-rich M3.0 dwarf star Wolf 294 that was obtained with the CARMENES spectrograph. We apply the TDTM approach to the CARMENES survey sample, which consists of 382 targets encompassing 22 357 optical and 20 314 near-infrared spectra, to correct for telluric absorption. The corrected spectra are coadded to construct template spectra for each of our targets. This library of telluric-free, high signal-to-noise ratio, high-resolution (ℛ > 80 000) templates comprises the most comprehensive collection of spectral M-dwarf data available to date, both in terms of quantity and quality, and is available at the project website.

Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Transmission Spectroscopy

“…We used the same standard operational mode as in the guaranteed time observations program for planet RV search (Ribas et al 2023), in which target spectra were obtained simultaneously with the spectra from a Fabry-Pérot etalon for wavelength calibration using variable exposure times limited by S/N = 150 and efficient scheduling (Garcia-Piquer et al 2017). We channeled the CARMENES data through our pipelines, which include spectrum extraction and nightly zero-point corrections (Ribas et al 2023, and references therein), telluric absorption corrections (Nagel et al 2023), and RV determination with serval (Zechmeister et al 2018). This work adopts the RVs measured with the CARMENES VIS channel, which are given in Appendix B.…”

An Earth-sized Planet on the Verge of Tidal Disruption

“…The spectra were reduced using the caracal (Caballero et al 2016) pipeline. We corrected the spectra for telluric absorption (Nagel et al 2023) and derived relative RVs with the serval pipeline (Zechmeister et al 2018). The RVs were further adjusted using measured nightly zero-point corrections (Trifonov et al 2020).…”