HORuS transmission spectroscopy of 55 Cnc e

Abstract

HORuS is a new high-resolution echelle spectrograph available on the 10.4 m GTC. We report on the first HORuS observations of a transit of the super-earth planet 55 Cnc e. We investigate the presence of Na i and Hα in its transmission spectrum and we explore the capabilities of HORuS for planetary transmission spectroscopy. Our methodology leads to residuals in the difference spectrum between the in-transit and out-of-transit spectra for the Na i doublet lines of (3.4 ± 0.4) × 10−4, which sets an upper limit to the detection of line absorption from the planetary atmosphere that is one order of magnitude more stringent that those reported in the literature. We demonstrate that we are able to reach the photon-noise limit in the residual spectra using HORuS to a degree that we would be able to easily detect giant planets with larger atmospheres. In addition, We modelled the structure, chemistry and transmission spectrum of 55 Cnc e using state-of-the-art open source tools.

The PEPSI Exoplanet Transit Survey (PETS) I: Investigating the presence of a silicate atmosphere on the super-Earth 55 Cnc e

“…Our non-detection of H agrees with previous investigations not finding evidence of hydrogen absorption for this planet (Ehrenreich et al 2012;Tabernero et al 2020). Other absorption signatures from species with strong opacities previously resolved on gaseous exoplanets such as Mg (Cauley et al 2019), K (Keles et al 2019) or Ca (Yan et al 2020) are not detected either for 55 Cnc e.…”

“…The non-detection of water (Esteves et al 2017;Jindal et al 2020) with the non-detection of light elements (Ehrenreich et al 2020;Zhang et al 2021) seems to make the water envelope scenario unlikely. A detectable thin silicate-vapor atmosphere scenario can not be strengthened either by Tabernero et al (2020) who did not find evidence for Na absorption or by this work not finding evidence of absorption for a variety of species. Overall, our work provide indications that favor the heavyweight atmospheric scenario.…”

“…However, the authors did not claim detection due to low significance of the Na absorption and variable Ca + signal. Another study on the rocky surface scenario for 55 Cnc e is presented by Tabernero et al (2020) investigating the absorption in the Na-D-lines and H line. The authors showed an upper limit of (3.4 ± 0.4) × 10 -4 to the presence of the Na-D-lines and (7 ± 1) × 10 -4 to the presence of the H line, not detecting absorption of these species.…”

Accurate Metallicities for Very Metal-Poor Stars from the Ca~II Infrared Triplet

“…G64-12 was observed with HORuS (Tabernero et al 2020; at GTC 1 on March 11 and July 2, 2019, HD122563 on January 13th 2020; and SDSS 134338 was observed on December 3, 2019. Data reduction was carried out with the chain 2 , which performs bias and flatfield correction, order tracing, extraction, and wavelength calibration.…”

A low-eccentricity migration pathway for a 13-h-period Earth analogue in a four-planet system

“…Assuming the planet is a black body with zero albedo, we estimated an equilibrium temperature of T eq = 1617 ± 41 K. As such, it is likely that TOI-500 b does not have a primary atmosphere inherited from the formation process and has undergone complete photo-evaporation during the formation and evolution processes [17]. The extreme vicinity to the host star could also have caused the formation of a metallic (secondary) atmosphere, possibly via volcanic out-gassing, as it might have happened on 55 Cancri e (see [19] for the estimated upper limit of atmospheric composition, and also [20]) and for planet Earth. A statistical analysis of the atmospheric predicted signal-to-noise (S/N) ratio of Earth-sized planets thus far discovered showed that TOI-500 b stands among the top 10 objects, meaning it is a promising target to perform atmospheric studies with current and future instruments (see Methods and Figure 9).…”