Project 3.6: Future upper atmospheric characterisation of exoplanets with spectroscopy (FOUR ACES)
The project FOUR ACES is led by David Ehrenreich. It is externally funded by the European Research Council through ERC Consolidator grant ERC-2016-COG: 724427 and is dedicated to the study of exoplanetery atmospheres.
This project will open a new path to characterise the atmospheres of exoplanets down to Earth-size objects, using the spatial extension of upper atmospheres as a magnifying glass to access the atmospheric properties. The tremendous energy received by exoplanets close to their stars leads to dramatic atmospheric expansion and escape, which could result in the formation of hot rocky super-Earths seen in recent years. While the escape mechanisms and evolutionary impact on planets and atmospheres remain debated, the atmospheric expansion gives rise to spectacular spectroscopic signatures in the ultra violet, only detectable with the Hubble Space Telescope (HST). The huge extended atmosphere observed escaping from a “warm Neptune” (Ehrenreich et al. 2015) represents a milestone on the road to the atmospheres of lower-mass, more temperate planets. HARPS spectroscopy from the ground also revealed the extreme conditions in the upper atmosphere of a “hot Jupiter”, probing the onset of atmospheric escape in the optical, linking the upper and lower atmospheres (Wyttenbach et al. 2015). FOUR ACES will consolidate these breakthroughs via a thorough exploitation of the vast amount of observations obtained for ~20 planets (400+ hours on HST and 300+ hours on HARPS and HARPS-N) in the wake of these results. Those data will be used to bind theories describing the lower and upper atmospheres of exoplanets, and determine how these are impacted by stellar activity. As new transit surveys will provide hundreds of exoplanets transiting bright stars, the reconnaissance capabilities of the ESA CHEOPS mission (2018–2022) will be used to cherrypick the very best ones for upper atmospheric characterisation.
The HARPS search for southern extra-solar planets. XLIV. Eight HARPS multi-planet systems hosting 20 super-Earth and Neptune-mass companions
The HARPS search for southern extra-solar planets. XXXVIII. Bayesian re-analysis of three systems. New super-Earths, unconfirmed signals, and magnetic cycles
Compositional Imprints in Density-Distance-Time: A Rocky Composition for Close-in Low-mass Exoplanets from the Location of the Valley of Evaporation
An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141
Radial velocity follow-up of GJ1132 with HARPS. A precise mass for planet b and the discovery of a second planet
The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits . III. The frequency of brown dwarfs and giant planets as companions to solar-type stars
The discovery of WASP-151b, WASP-153b, WASP-156b: Insights on giant planet migration and the upper boundary of the Neptunian desert
The RoPES project with HARPS and HARPS-N. I. A system of super-Earths orbiting the moderately active K-dwarf HD 176986
High-energy environment of super-Earth 55 Cancri e. I. Far-UV chromospheric variability as a possible tracer of planet-induced coronal rain