An atmosphere around the super-Earth 55 Cancri e
Exoplanetary systems: past, present, and future
Angelos Tsiaras
One of the most successful instruments for observing exoplanetary atmospheres is the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope (HST). In particular, the use of the spatial scanning technique has given us the opportunity for even more efficient observations of the brightest targets, achieving the necessary precision of 10 – 100 ppm. With such data and new advanced reduction and statistical techniques, we were able to detect modulations in the spectrum of the hot super-Earth 55 Cancri e, which suggest the existence of a light-weight atmosphere around this planet. Given the brightness of 55 Cancri, the observers adopted a very long scanning length and a very high scanning speed which we took into account as they can introduce systematics when coupled with the geometrical distortions of the instrument. Our fully Bayesian spectral retrieval code, T-REx, has identified HCN to be the most likely molecular candidate able to explain the observed features. While additional spectroscopic observations in a broader wavelength range in the infrared will be needed to confirm the HCN detection, we used a chemical model, developed with combustion specialists, to explain its possible. This model indicates that relatively high mixing ratios of HCN may be caused by a high C/O ratio, suggesting this super-Earth is a carbon-rich environment even more exotic than previously thought.


16:30 - 18:00
EX - LT3 (320)