Hot Jupiters receive intense irradiation from their stellar hosts. The resulting extreme environments in their atmospheres allow us to study the conditions that drive planetary atmospheric dynamics, e.g., global–scale winds. General circulation models predict day–to–nightside winds and equatorial jets with speeds of the order of a few km s–1. To test these models, we apply high–resolution transmission spectroscopy using the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) spectrograph on the Large Binocular Telescope to study the atmosphere of KELT–9 b, an ultrahot Jupiter and currently the hottest known planet. We measure ~10 km s–1 day–to–nightside winds traced by Fe II features in the planet’s atmosphere. This is at odds with previous literature (including data taken with PEPSI), which report no significant day–to–nightside winds on KELT–9 b. We identify the cause of this discrepancy as due to an inaccurate ephemeris for KELT–9 b in previous literature.
Read more: Pai Asnodkar et al. 2022, AJ, 163, 155