Na I and H$\alpha$ absorption features in the atmosphere of MASCARA-2b/KELT-20b

摘要: We have used the HARPS-North high resolution spectrograph ($\mathcal{R}$=115 000) at TNG to observe one transit of highly irradiated planet MASCARA-2b/KELT-20b. Using only observation, we are able clearly resolve spectral features atomic sodium (Na I) doublet and H$\alpha$ line in its atmosphere, measuring absorption depths 0.17$\pm$0.03$\%$ 0.59$\pm$0.08$\%$ for a 0.75 $\AA$ passband, respectively. These absorptions corroborated with transmission measured from their respective light curves, which show large Rossiter-McLaughlin effect. In case H$\alpha$, this corresponds an effective radius $R_{\lambda}/R_P$=1.20$\pm$0.04. While S/N final spectrum is not sufficient adjust different temperature profiles lines, find that higher temperatures than equilibrium needed explain lines contrast. Particularly, Na I core require T=4210$\pm$180K requires T=4330$\pm$520K. MASCARA-2b, like other planets orbiting A-type stars, receives amount UV energy host star. This excites hydrogen produces absorption, leading expansion abrasion atmosphere. The study Balmer would allow determination atmospheric profile calculation lifetime residual observed H$\beta$ H$\gamma$ but they statistically significant. More observations confirm our findings build up enough explore presence planetary absorptions.