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Transmission spectroscopy of the sodium doublet in WASP-17b with the VLT

Published online by Cambridge University Press:  10 November 2011

Patricia L. Wood  and
Pierre F. L. Maxted
Patricia L. Wood
Affiliation:
Keele University, Staffordshire ST5 5BG, UK email: [email protected]
Pierre F. L. Maxted
Affiliation:
Keele University, Staffordshire ST5 5BG, UK email: [email protected]
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Abstract

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The detection of sodium absorption during primary transit implies the presence of an atmosphere around an extrasolar planet. WASP-17b (Anderson et al. 2010a) is the least dense known planet, with a radius twice that of Jupiter. It orbits an F6-type star, and its low gravity gives its atmosphere a very large scale height. The sodium transit depth is expected to be 4.1 – 5.2 times deeper than for HD 209458b (Seager & Sasselov 2000). We obtained 24 spectra with the GIRAFFE spectrograph on the VLT, 8 during transit. We measured the flux in the sodium doublet at 5889.95 Å and 5895.92 Å using bandpasses 0.75, 1.5, 3.0 and 6.0 Å. We find a transit depth of 0.55±0.13% at 1.5 Å (4.3σ). WASP-17b therefore has an atmosphere which is depleted in sodium compared to predictions.

Keywords

planetary systemsstars: individual (WASP-17)techniques: spectroscopic
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S276: The Astrophysics of Planetary Systems: Formation, Structure, and Dynamical Evolution , October 2010 , pp. 491 - 492
Copyright
Copyright © International Astronomical Union 2011

References

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