The Peculiar Atmospheric Chemistry of KELT-9b

Kitzmann, Daniel; Heng, Kevin; Rimmer, Paul B.; Hoeijmakers, Jens; Tsai, Shang-Min; Malik, Matej; Lendl, Monika; Deitrick, Russell John; Demory, Brice-Olivier (2018). The Peculiar Atmospheric Chemistry of KELT-9b. Astrophysical journal, 863(2), p. 183. Institute of Physics Publishing IOP 10.3847/1538-4357/aace5a

Preview

Text Kitzmann_2018_ApJ_863_183.pdf - Published Version Available under License Creative Commons: Attribution (CC-BY). Download (2MB) | Preview

The atmospheric temperatures of the ultra-hot Jupiter KELT-9b straddle the transition between gas giants and stars, and therefore between two traditionally distinct regimes of atmospheric chemistry. Previous theoretical studies assume the atmosphere of KELT-9b to be in chemical equilibrium. Despite the high ultraviolet flux from KELT-9, we show using photochemical kinetic calculations that the observable atmosphere of KELT-9b is predicted to be close to chemical equilibrium, which greatly simplifies any theoretical interpretation of its spectra. It also makes the atmosphere of KELT-9b, which is expected to be cloud-free, a tightly constrained chemical system that lends itself to a clean set of theoretical predictions. Due to the lower pressures probed in transmission (compared to emission) spectroscopy, we predict the abundance of water to vary by several orders of magnitude across the atmospheric limb depending on temperature, which makes water a sensitive thermometer. Carbon monoxide is predicted to be the dominant molecule under a wide range of scenarios, rendering it a robust diagnostic of the metallicity when analyzed in tandem with water. All of the other usual suspects (acetylene, ammonia, carbon dioxide, hydrogen cyanide, methane) are predicted to be subdominant at solar metallicity, while atomic oxygen, iron, and magnesium are predicted to have relative abundances as high as 1 part in 10,000. Neutral atomic iron is predicted to be seen through a forest of optical and near-infrared lines, which makes KELT-9b suitable for high-resolution ground-based spectroscopy with HARPS-N or CARMENES. We summarize future observational prospects of characterizing the atmosphere of KELT-9b.

Interest & Impact

Downloads

131 since deposited on 03 Jun 2019
22 in the past 12 months

Citations

5 Citations in Web of Science ®
6 Citations in Scopus

Search

in Google Scholar™

Services

Actions (login required)

Edit item

Actions (login required)

Edit item