Ultra-hot Jupiters are gas giants planets whose dayside temperature , due to the strong irradiation received from the host star , is greater than 2200 K. These kind of objects are perfect laboratories to study chemistry of exoplanetary upper atmospheres via transmission spectroscopy .
Exo-atmospheric absorption features are buried in the noise of the in-transit residual spectra .
However we can retrieve the information of hundreds of atmospheric absorption lines by performing a cross-correlation with an atmospheric transmission model , which allows us to greatly increase the exo-atmospheric signal .
At the high-spectral resolution of our data , the Rossiter-McLaughlin effect and centre-to-limb variation have a strong contribution .
Here , we present the first detection of Fe I and the confirmation of absorption features of Fe II in the atmosphere of the ultra-hot Jupiter MASCARA-2b/KELT-20b , by using three transit observations with HARPS-N. After combining all transit observations we find a high cross-correlation signal of Fe I and Fe II with signal-to-noise ratios of 10.5 \pm 0.4 and 8.6 \pm 0.5 , respectively .
The peak absorption for both species appear to be blue-shifted with velocities of -6.3 \pm 0.8 km s ^ { -1 } for Fe I and -2.8 \pm 0.8 km s ^ { -1 } for Fe II , suggesting the presence of winds from the day- to night-side of the planet ’ s atmosphere .
These results confirm previous studies of this planet and add a new atomic species ( Fe I ) to the long list of detected species in the atmosphere of MASCARA-2b , making it , together with KELT-9b , the most feature-rich ultra-hot Jupiter to date .