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Description
We analyze the transmission spectrum around the Na I doublet at 589nm of the extrasolar planet WASP-69b, and compare the analysis to that of the well-know hot Jupiter HD 189733b. We also present the analysis of the Rossiter-McLaughlin (RM) effect for WASP-69b. We observed two transits of WASP-69b with the HARPS-North spectrograph (R=115 000) at the TNG telescope. We perform a telluric contamination subtraction based on the comparison between the observed spectra and a telluric water model. Then, the common steps of the differential spectroscopy are followed to extract the transmission spectrum. The method is tested with archival transit data of the extensively studied exoplanet HD 189733b, obtained with the HARPS-South spectrograph at ESO 3.6m telescope, and then applied to WASP-69b data. For HD 189733b, we spectrally resolve the NaI doublet and measure line contrasts of 0.72+/-0.05% (D2) and 0.51+/-0.05% (D1), and FWHMs of 0.64+/-0.04{AA} (D2) and 0.60+/-0.06{AA} (D1), in agreement with previously published results. For WASP-69b only the contrast of the D2 line can be measured (5.8+/-0.3%). This corresponds to a detection at the 5sigma-level of excess absorption of 0.5+/-0.1% in a passband of 1.5{AA}. By measuring the RM effect, we get an angular rotation of 0.24^+0.02^_-0.01_rad/day and a sky-projected angle between the stellar rotation axis and the normal of orbit plane of 0.4^+2.0^_-1.9_{deg} FOR wasP-69b. Similar results to those previously presented in the literature are obtained for the RM analysis of HD 189733b.
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