LRG-BEASTS: Sodium absorption and Rayleigh scattering in the atmosphere of WASP-94A b using NTT/EFOSC2

We present an optical transmission spectrum for WASP-94A b, the first atmospheric characterisation of this highly-inflated hot Jupiter. The planet has a reported radius $1.72^{+0.06}_{-0.05}$ R$_{\textrm{Jup}}$, mass only $0.456^{+0.032}_{-0.036}$ M$_{\textrm{Jup}}$, and equilibrium temperature $1508 \pm 75$ K. observed transit spectroscopically with EFOSC2 instrument on ESO New Technology Telescope (NTT) at La Silla, Chile: use NTT/EFOSC2 spectroscopy. achieved average transit-depth precision $128$ ppm bin widths $\sim200$ Angstrom. This high was in part by linking Gaussian Process hyperparameters across all wavelength bins. resulting spectrum, spanning range $3800 - 7140$ Angstrom, exhibits sodium absorption significance $4.9\sigma$, suggesting relatively cloud-free atmosphere. signal may be broadened, best fitting width $78_{-32}^{+67}$ Angstrom contrast to instrumental resolution $27.2 0.2$ also detect steep slope blue end indicating presence Rayleigh scattering atmosphere b. Retrieval models show evidence super-Rayleigh potential causes are discussed. Finally, we find narrow cores CaII H&K lines WASP-94A, star is enshrouded gas escaping