Ground-based detection of Calcium and possibly Scandium and Hydrogen in the atmosphere of HD 209458b

TL;DR

This study re-analyzed ground-based spectra of HD 209458b, detecting calcium, possibly scandium and hydrogen, and refining atmospheric composition understanding through an innovative telluric correction and automated feature search.

Contribution

It introduces a new telluric correction method based on airmass variations and an automated algorithm for detecting atmospheric absorption features in exoplanet spectra.

Findings

Detected calcium absorption at 6162.17A and 6493.78A

Possible detection of scandium at 5526.79A

First ground-based detection of hydrogen in HD 209458b

Abstract

Context: Since the first exoplanetary atmosphere detection using the Hubble Space Telescope, characterization of exoplanet atmospheres from the ground have been playing an increasingly important role in the analysis of such atmospheres thanks to the enhancement of telluric correction techniques. At present, several species have been discovered in the atmosphere of HD 209458b, all of them consistent with theoretical models. Aims: Data acquired using the High Dispersion Spectrograph on the Subaru telescope are re-analysed. We expect to discover new species in the atmosphere of the exoplanet HD 209458b. In addition to shed light on the atmospheric composition, we will derive the radial extension of the absorbents present in the atmosphere of the exoplanet. Methods: We present an alternative method to correct the telluric effects through the analysis of variations in spectral lines with the airmass. To search absorptions due to an exoplanetary atmosphere we implemented an algorithm to automatically search for all the features presenting an atmospheric signature in the transmission spectrum and through the wavelength range in the data. In order to estimate uncertainties we perform a bootstrapping analysis. Results: Absorption excess due to the transitions of Calcium at 6162.17A and 6493.78A, Scandium at 5526.79A, Hydrogen at 6562.8A and Sodium doublet are detected in the transmission spectrum at a level of -0.079+-0.012%, -0.138+-0.013%, -0.059+-0.012%, -0.123+-0.012%, -0.071+-0.016% using pass-bands of 0.5A, 0.4A, 0.5A, 1.1A and 0.6A, respectively. Conclusions: Models predict strong absorption in the Sodium resonance Doublet which was previously detected, also in this analysis. However, this is the first report of Calcium and possibly Scandium in HD 209458b, including the possible ground-based detection of Hydrogen. ... (continues)