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Description
Ultra-hot Jupiters orbit very close to their host star and consequently receive strong irradiation, causing their atmospheric chemistry to be different from the common gas giants. Here, we have studied the atmosphere of one of these particular hot planets, MASCARA- 2b/KELT-20b, using four transit observations with high resolution spectroscopy facilities. Three of these observations were performed with HARPS-N and one with CARMENES. Additionally, we simultaneously observed one of the transits with MuSCAT2 to monitor possible spots in the stellar surface. At high resolution, the transmission residuals show the effects of Rossiter-McLaughlin and centre- to-limb variations from the stellar lines profiles, which we have corrected to finally extract the transmission spectra of the planet. We clearly observe the absorption features of CaII, FeII, NaI, H{alpha}, and H{beta} in the atmosphere of MASCARA-2b, and indications of H{gamma} and MgI at low signal-to-noise ratio. In the case of NaI, the true absorption is difficult to disentangle from the strong telluric and interstellar contamination. The results obtained with CARMENES and HARPS-N are consistent, measuring an H{alpha} absorption depth of 0.68+/-0.05 and 0.59+/-0.07%, and NaI absorption of 0.11+/-0.04 and 0.09+/-0.05% for a 0.75{AA} passband, in the two instruments respectively. The H{alpha} absorption corresponds to ~1.2Rp, which implies an expanded atmosphere, as a result of the gas heating caused by the irradiation received from the host star. For H{beta} and H{gamma} only HARPS-N covers this wavelength range, measuring an absorption depth of 0.28+/-0.06 and 0.21+/-0.07%, respectively. For CaII, only CARMENES covers this wavelength range measuring an absorption depth of 0.28+/-0.05, 0.41+/-0.05 and 0.27+/-0.06% for CaII {lambda}8498{AA}, {lambda}8542{AA} and {lambda}8662{AA} lines, respectively. Three additional absorption lines of FeII are observed in the transmission spectrum by HARPS-N (partially covered by CARMENES), measuring an average absorption depth of 0.08+/-0.04% (0.75{AA} passband). The results presented here are consistent with theoretical models of ultra-hot Jupiters atmospheres, suggesting the emergence of an ionised gas on the day-side of such planets. Calcium and iron, together with other elements, are expected to be singly ionised at these temperatures and be more numerous than its neutral state. The Calcium triplet lines are detected here for the first time in transmission in an exoplanet atmosphere. Description: The transmission spectra and of MASCARA-2b/KELT-20b are presented. Three transits with HARPS-North at TNG telescope were retrieved and one transit with CARMENES at 3.5 telescope at CAHA Observatory. For each spectral line the transmission spectra of MASCARA-2b/KELT-20b after correcting the CLV + RME are presented here. We note that in some cases the transmission spectrum of a specific line also includes transmission lines located close to the main spectral line (e.g. in case of NaI doublet). However, it is important to note that only the main spectral line of each file (see files name) includes the CLV+RME corrections. You need to work with specific files.
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