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, Serena Benatti, Katia Biazzo, Andrea Bignamini, Franscesco Borsa, Ilaria Carleo, Riccardo Claudi, Rosario Cosentino, Elvira CovinoMario Damasso, Silvano Desidera, Paolo Giacobbe, Avet Harutyunyan, Antonino Francesco Lanza, Giuseppe Leto, Antonio Maggio, Jesus Maldonado, Luigi Mancini, Giuseppina Micela, Emilio Molinari, Isabella Pagano, Giampaolo Piotto, Ennio Poretti, Monica Rainer, Gaetano Scandariato, Alessandro Sozzetti, Romain Allart, Luca Borsato, Giovanni Bruno, Luca Di Fabrizio, David Ehrenreich, Aldo Fiorenzano, Giuseppe Frustagli, Baptiste Lavie, Christophe Lovis, Antonio Magazz, Domenico Nardiello, Marco Pedani, Riccardo Smareglia

Research output: Contribution to journalArticlepeer-review

81 Scopus citations


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 cross-correlation analysis. We also adapt the concept of contribution 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.

Original languageEnglish (US)
Article numberL27
JournalAstrophysical Journal Letters
Issue number2
StatePublished - May 10 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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