Neutral Iron Emission Lines from the Dayside of KELT-9b: The GAPS Program with HARPS-N at TNG XX

Lorenzo Pino, Jean-Michel Désert, Matteo Brogi, Luca Malavolta, Aurélien Wyttenbach, Michael Line, Jens Hoeijmakers, Luca Fossati, Aldo Stefano Bonomo, Valerio Nascimbeni, Vatsal Panwar, Laura Affer (+38 others)
2020 Astrophysical Journal Letters  
We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We detect neutral iron lines from the dayside of KELT-9b (T eq ∼4000 K). We combined thousands of spectrally resolved lines observed during one night with the HARPS-N spectrograph (R∼115,000), mounted at the Telescopio Nazionale Galileo. We introduce a novel statistical approach to extract the planetary parameters from the binary mask crosscorrelation analysis. We also adapt the concept of
more » ... on function to the context of high spectral resolution observations, to identify the location in the planetary atmosphere where the detected emission originates. The average planetary line profile intersected by a stellar G2 binary mask was found in emission with a contrast of 84±14 ppm relative to the planetary plus stellar continuum (40% ± 5% relative to the planetary continuum only). This result unambiguously indicates the presence of an atmospheric thermal inversion. Finally, assuming a modeled temperature profile previously published, we show that an iron abundance consistent with a few times the stellar value explains the data well. In this scenario, the iron emission originates at the 10 −3 -10 −5 bar level. Unified Astronomy Thesaurus concepts: Exoplanet atmospheres (487); Exoplanet atmospheric composition (2021); High resolution spectroscopy (2096)
doi:10.3847/2041-8213/ab8c44 fatcat:6qfpho2nprcedjpi6gdch4uigu