Signs of Ionized Iron Beyond the Roche Lobe of HD 209458b from NUV Observations
Abstract
Ultraviolet transit observations probe the upper atmosphere of exoplanets, where mass loss occurs. Our analysis of NUV transmission observations of HD 209458b shows evidence for ionized iron beyond the planet's Roche lobe, and no evidence for neutral iron, neutral magnesium, nor ionized magnesium. These results pose a conundrum for current theoretical models. While the upper-atmosphere observations indicate that hydrodynamic escape can carry up the heavy iron atoms, the lower-atmosphere observations indicate that iron should be trapped into aerosol condensates. This intricate relationship between lower- and upper-atmosphere properties makes the combination UV and optical/infrared observations more valuable than the sum of it parts when characterizing an atmosphere. Only a few targets enable both upper- and lower-atmosphere characterization, thus, further NUV observations of HD 209458b would be invaluable to improve our understanding of exoplanet atmospheres.
- Publication:
-
EPSC-DPS Joint Meeting 2019
- Pub Date:
- September 2019
- Bibcode:
- 2019EPSC...13.1817C