Seminars at FGG
High resolution transmission spectroscopy of KELT-18b:probing a hot Jupiter at the ultra-hot transition
Speaker: Moreno Monticelli (Osservatorio Astronomico di Brera - INAF (Italy))
Date and time: 2026-11-05 12:30
KELT-18b is a highly irradiated giant planet (with equilibrium temperature of 2085K) located in the transition regime between hot and ultra-hot Jupiters, where molecular dissociation, refractory chemistry, and changes in atmospheric thermal structure become increasingly important. We present a multi-instrument, optical-to-near-infrared study of its atmosphere using high-resolution transmission spectroscopy. The analysis reveals signatures from different atmospheric regions, including neutral iron and OH, together with Hα and metastable He I tracing the highly irradiated upper atmosphere. These observations make KELT-18b a valuable laboratory for investigating the atmospheric changes occurring across the hot-to-ultra-hot Jupiter transition. We also discuss upcoming high-resolution dayside observations aimed at probing its thermal structure and searching for evidence of a temperature inversion.