Detection of sodium absorption in WASP-17b with Magellan

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 Nai D doublet spectral region. Using the interstellar sodium absorption lines as reference, we detect a 0.58 +/- 0.13 per cent transit signal, with 4.5s confidence, at 1.5 angstrom 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.