Publication Date:
2013-11-23
Description:
We report a 4.8 detection of water absorption features in the day side spectrum of the hot Jupiter HD 189733 b. We used high-resolution ( R ~ 100 000) spectra taken at 3.2 μm with CRIRES on the VLT to trace the radial-velocity shift of the water features in the planet's day side atmosphere during 5 h of its 2.2 d orbit as it approached secondary eclipse. Despite considerable telluric contamination in this wavelength regime, we detect the signal within our uncertainties at the expected combination of systemic velocity ( $V_{\rm sys}=-3^{+5}_{-6}$ km s –1 ) and planet orbital velocity ( $K_{\rm p}=154^{+14}_{-10}$ km s –1 ), and determine a H 2 O line contrast ratio of (1.3 ± 0.2) 10 –3 with respect to the stellar continuum. We find no evidence of significant absorption or emission from other carbon-bearing molecules, such as methane, although we do note a marginal increase in the significance of our detection to 5.1 with the inclusion of carbon dioxide in our template spectrum. This result demonstrates that ground-based, high-resolution spectroscopy is suited to finding not just simple molecules like CO, but also to more complex molecules like H 2 O even in highly telluric contaminated regions of the Earth's transmission spectrum. It is a powerful tool that can be used for conducting an immediate census of the carbon- and oxygen-bearing molecules in the atmospheres of giant planets, and will potentially allow the formation and migration history of these planets to be constrained by the measurement of their atmospheric C/O ratios.
Print ISSN:
1745-3925
Electronic ISSN:
1745-3933
Topics:
Physics
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