Chromatic line-profile tomography to reveal exoplanetary atmospheres: application to HD 189733b
Journal
Date Issued
2016
Author(s)
Abstract
Context. Transmission spectroscopy can be used to constrain the properties of exoplanetary atmospheres. During a transit, the light blocked from the atmosphere of the planet leaves an imprint in the light coming from the star. This has been shown for many exoplanets with both photometry and spectroscopy, using different analysis methods. Aims: We test chromatic line-profile tomography as a new tool to investigate exoplanetary atmospheres. The signal imprinted on the cross-correlation function (CCF) by a planet transiting its star is dependent on the planet-to-star radius ratio. We want to verify whether the precision reachable on the CCF obtained from a subset of the spectral orders of the HARPS spectrograph is high enough to determine the radius of a planet at different wavelengths. Methods: We analyze HARPS archival data of three transits of HD 189733b. We divide the HARPS spectral range into seven broadbands, calculating for each band the ratio between the area of the out-of-transit CCF and the area of the signal imprinted by the planet on it during the full part of the transit. We take into account the effect of the limb darkening using the theoretical coefficients of a linear law. Averaging the results of three different transits allows us to obtain a good-quality broadband transmission spectrum of HD 189733b with a greater precision than that of the chromatic Rossiter McLaughlin effect. Results: We proved that chromatic line-profile tomography is an interesting way to reveal broadband transmission spectra of exoplanets: our analysis of the atmosphere of HD 189733b is in agreement with other ground- and space-based observations. The independent analysis of different transits emphasizes the probability that stellar activity plays a role in the extracted transmission spectrum. Therefore, care should be taken when claiming that Rayleigh scattering is present in the atmosphere of exoplanets orbiting active stars using only one transit.
Volume
590
Start page
A84
Issn Identifier
0004-6361
Ads BibCode
2016A&A...590A..84B
Rights
open.access
File(s)![Thumbnail Image]()
![Thumbnail Image]()
Loading...
Name
chromatic_tomography_astroph.pdf
Description
postprint
Size
3.12 MB
Format
Adobe PDF
Checksum (MD5)
207ad2e1420a5dc44567b9ec5cf55201
Loading...
Name
aa28334-16.pdf
Description
pdf editoriale
Size
2.9 MB
Format
Adobe PDF
Checksum (MD5)
cd5c4c5dc68eaeda769693878dac2403