Detection of sodium absorption in WASP-17b with magellan

Abstract

We present the detection of sodium absorption in the atmosphere of the extrasolar planet WASP-17b, an inflated 'hot Jupiter' in a tight orbit around an F6 dwarf. In-transit observations of WASP-17 made with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the 6.5-m Magellan Telescope were analysed for excess planetary atmospheric absorption in the Na I 'D' doublet spectral region. Using the interstellar sodium absorption lines as reference, we detect a 0.58 ± 0.13 per cent transit signal, with 4.5σ confidence, at 1.5Å bandwidth around the stellar sodium absorption feature. This result is consistent with the previous Very Large Telescope detection of sodium in WASP-17b, confirming that the planet has a highly inflated atmosphere. © 2012 The Authors Monthly Notices of the Royal Astronomical Society. © 2012 RAS.