Hot Jupiter in Binary System WASP-94Ab: Observations reveal Sodium Feature and Steep Scattering Slope

We present evidence for pressure-broadened sodium absorption and a steep scattering slope, using low-resolution optical transmission spectra of the hot Jupiter WASP-94Ab. Broad sodium is an indicator of a cloud-free atmosphere, suggesting the highly-inflated WASP-94Ab is an excellent target for molecular abundance determination using infrared spectroscopy.

Our low-resolution study of the atmosphere of this exoplanet, a highly-inflated hot Jupiter with a radius of 1.7 Jupter radii and a mass of 0.5 Jupiter masses and an estimated equilibrium temperature of 1500 K in the wavelength range of 3800 - 7140 Å has revealed a clear atmosphere with a 4.9σ sodium absorption and a scattering slope through the LRG-BEASTS survey. It was measured with the EFOSC2 spectrograph on the ESO New Technology Telescope - the first time this instrument has been used for transmission spectroscopy. The ongoing work on high resolution observations from HARPS (taken as part of the HEARTS survey) is probing the Doppler shifts of the sodium line doublet.