Assessing telluric correction methods for Na detections with high-resolution exoplanet transmission spectroscopy
arXiv:2101.05283 · doi:10.1093/mnras/stab134
Abstract
Using high-resolution ground-based transmission spectroscopy to probe exoplanetary atmospheres is difficult due to the inherent telluric contamination from absorption in Earth's atmosphere. A variety of methods have previously been used to remove telluric features in the optical regime and calculate the planetary transmission spectrum. In this paper we present and compare two such methods, specifically focusing on Na detections using high-resolution optical transmission spectra: (1) calculating the telluric absorption empirically based on the airmass, and (2) using a model of the Earth's transmission spectrum. We test these methods on the transmission spectrum of the hot Jupiter HD 189733 b using archival data obtained with the HARPS spectrograph during three transits. Using models for Centre-to-Limb Variation and the Rossiter-McLaughlin effect, spurious signals which are imprinted within the transmission spectrum are reduced. We find that correcting tellurics with an atmospheric model of the Earth is more robust and produces consistent results when applied to data from different nights with changing atmospheric conditions. We confirm the detection of sodium in the atmosphere of HD 189733 b, with doublet line contrasts of -0.64 0.07 % (D2) and -0.53 0.07 % (D1). The average line contrast corresponds to an effective photosphere in the Na line located around 1.13 R. We also confirm an overall blueshift of the line centroids corresponding to net atmospheric eastward winds with a speed of 1.8 1.2 km/s. Our study highlights the importance of accurate telluric removal for consistent and reliable characterisation of exoplanetary atmospheres using high-resolution transmission spectroscopy.
Published in MNRAS, 13 pages, 9 figures. Updated with proof corrections
References in corpus (27)
- Molecfit: A general tool for telluric absorption correction. I. Method and application to ESO instruments
- Improved parameters for extrasolar transiting planets
- Detection of atmospheric haze on an extrasolar planet: The 0.55 - 1.05 micron transmission spectrum of HD189733b with the Hubble Space Telescope
- Molecfit: A general tool for telluric absorption correction II. Quantitative evaluation on ESO-VLT X-Shooter spectra
- Sodium Absorption From the Exoplanetary Atmosphere of HD189733b Detected in the Optical Transmission Spectrum
- Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
- Rayleigh scattering in the transit spectrum of HD 189733b
- Thermal structure of an exoplanet atmosphere from phase-resolved emission spectroscopy
- Water Vapor in the Spectrum of the Extrasolar Planet HD 189733b: 1. the Transit
- Spectrally resolved detection of sodium in the atmosphere of HD189733b with the HARPS spectrograph
- Ground-based detection of sodium in the transmission spectrum of exoplanet HD209458b
- Mass-Metallicity Trends in Transiting Exoplanets from Atmospheric Abundances of HO, Na, and K
- A spectral survey of an ultra-hot Jupiter: Detection of metals in the transmission spectrum of KELT-9 b
- Atmospheric escape from HD 189733b observed in HI Lyman-alpha: detailed analysis of HST/STIS September 2011 observations
- High-resolution confirmation of an extended helium atmosphere around WASP-107b
- GENESIS: New Self-Consistent Models of Exoplanetary Spectra
- Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) - II. A broadened sodium feature on the ultra-hot giant WASP-76b
- VLT FORS2 comparative transmission spectroscopy: Detection of Na in the atmosphere of WASP-39b from the ground
- Detection of sodium in the atmosphere of WASP-69b
- Search for water vapor in the high-resolution transmission spectrum of HD189733b in the visible
- Confirmation of WASP-107b's extended Helium atmosphere with Keck II/NIRSPEC
- Wind of Change: retrieving exoplanet atmospheric winds from high-resolution spectroscopy
- Exoplanetary atmospheric sodium revealed by the orbital motion. Narrow-band transmission spectroscopy of HD 189733b with UVES
- Potassium detection in the clear atmosphere of a hot-Jupiter: FORS2 transmission spectroscopy of WASP-17b
- Evidence for the Direct Detection of the Thermal Spectrum of the Non-Transiting Hot Gas Giant HD 88133 b
- High resolution transmission spectrum of the Earth's atmosphere -- Seeing Earth as an exoplanet using a lunar eclipse
- A Non-isothermal Theory for Interpreting Sodium Lines in Transmission Spectra of Exoplanets