DETECTION OF AN ATMOSPHERE AROUND THE SUPER-EARTH 55 CANCRI E

DETECTION OF AN ATMOSPHERE AROUND THE SUPER-EARTH 55 CANCRI E

ABSTRACT We report the analysis of two new spectroscopic observations in the near-infrared of the super-Earth 55 Cancri e, obtained with the WFC3 camera on board the Hubble Space Telescope. 55 Cancri e orbits so close to its parent star that temperatures much higher than 2000 K are expected on its s...

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Bibliographic Details
Published in:The Astrophysical journal 2016-04, Vol.820 (2), p.99-99
Main Authors: Tsiaras, A., Rocchetto, M., Waldmann, I. P., Venot, O., Varley, R., Morello, G., Damiano, M., Tinetti, G., Barton, E. J., Yurchenko, S. N., Tennyson, J.
Format: Article
Language:eng
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Atmospheres
CARBON
Channels
Combustion
Confidence intervals
DATA ANALYSIS
DETECTION
Hubble Space Telescope
HYDROCYANIC ACID
HYDROGEN
methods: data analysis
methods: statistical
MIXING RATIO
PLANETARY ATMOSPHERES
PLANETS
planets and satellites: atmospheres
planets and satellites: individual (55 Cancri e)
SATELLITE ATMOSPHERES
SATELLITES
Scanning
SPACE
STARS
Straight lines
techniques: spectroscopic
TELESCOPES
VELOCITY
Wavelengths
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Summary:ABSTRACT We report the analysis of two new spectroscopic observations in the near-infrared of the super-Earth 55 Cancri e, obtained with the WFC3 camera on board the Hubble Space Telescope. 55 Cancri e orbits so close to its parent star that temperatures much higher than 2000 K are expected on its surface. Given the brightness of 55 Cancri, the observations were obtained in scanning mode, adopting a very long scanning length and a very high scanning speed. We use our specialized pipeline to take into account systematics introduced by these observational parameters when coupled with the geometrical distortions of the instrument. We measure the transit depth per wavelength channel with an average relative uncertainty of 22 ppm per visit and find modulations that depart from a straight line model with a 6 confidence level. These results suggest that 55 Cancri e is surrounded by an atmosphere, which is probably hydrogen-rich. Our fully Bayesian spectral retrieval code, -REx, has identified HCN to be the most likely molecular candidate able to explain the features at 1.42 and 1.54 m. While additional spectroscopic observations in a broader wavelength range in the infrared will be needed to confirm the HCN detection, we discuss here the implications of such a result. Our chemical model, developed with combustion specialists, indicates that relatively high mixing ratios of HCN may be caused by a high C/O ratio. This result suggests this super-Earth is a carbon-rich environment even more exotic than previously thought.
ISSN:0004-637X
1538-4357