The GAPS programme at TNG LX Atmospheric characterisation of KELT-9 b via single-line analysis: Detection of six H I Balmer lines, Na I, Ca I, Ca II, Fe I, Fe II, Mg I, Ti II, Sc II, and Cr II

• DOI: 10.48550/arxiv.2409.01779
• Publication Date: 2024-09-03
• Authors: M. C. D’Arpa; Andrea Saba; F. Borsa; L. Fossati; G. Micela; C. Di Maio; M. Stangret; Giovanni Tripodo; L. Affer; A. S. Bonomo; S. Benatti; Matteo Brogi; V. Fardella; A. F. Lanza; G. Guilluy; J. Maldonado; G. Mantovan; V. Nascimbeni; L. Pino; G. Scandariato; D. Sicilia; A. Sozzetti; R. Spinelli; G. Andreuzzi; A. Bignamini; R. Claudi; S. Desidera; A. Ghedina; C. Knapic; V. Lorenzi
• Keywords: Balmer series; Line (geometry)

We analysed six primary transits of the ultra-hot Jupiter KELT-9,b obtained with HARPS-N high-resolution spectrograph in context Global Architecture Planetary Systems (GAPS2) project, to characterise atmosphere via single-line analysis. extracted transmission spectrum each individual line by comparing master out-of-transit in-transit spectra and computing weighted average tomography planet reference frame. corrected for centre-to-limb variation Rossiter-McLaughlin effect modelling region star disc obscured during transit subtracting it from master-out spectrum. detected all observable lines Balmer series within wavelength range, H$\alpha$ H$\zeta$, a significance exceeding 5$\sigma$. focussed on metal species, detecting Na I, Ca II, Fe Mg Ti Sc Cr II lines. This is first detection an exoplanet H$\epsilon$ H$\zeta$ lines, as well II. Our detections are supported comparison published synthetic KELT-9b accounting non-local thermodynamic equilibrium effects. The results underline presence systematic blueshift due night-side day-side winds. analysis allowed us not only assess atomic species KELT-9 b, but also further local stratification atmosphere. Coupling height distribution velocity shift retrieved, we acknowledged Moreover, study rotational broadening different supports prediction tidally locked rotating rigid body.