English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We present transmission spectroscopy of the hot-Jupiter WASP-31b using FORS2on the VLT during two primary transits. The observations cover a wavelengthrange of $\approx$400-840nm. The light curves are corrupted by significantsystematics, but these were to first order invariant with wavelength and couldbe removed using a common-mode correction derived from the white light curves.We reach a precision in the transit depth of $\approx$140 ppm in 15 nm bins,although the precision varies significantly over the wavelength range. OurFORS2 observations confirm the cloud-deck previously inferred using HST/STIS.We also re-analyse the HST/STIS data using a Gaussian process model, findingexcellent agreement with earlier measurements. We reproduce the Rayleighscattering signature at short wavelengths ($\lesssim$5300 $\AA$) and thecloud-deck at longer wavelengths. However, our FORS2 observations appear torule out the large potassium feature previously detected using STIS, yet it isrecovered from the HST/STIS data, although with reduced amplitude andsignificance ($\approx$2.5$\sigma$). The discrepancy between our results andthe earlier STIS detection of potassium ($\approx$4.3$\sigma$) is either aresult of telluric contamination of the ground-based observations, or anunderestimate of the uncertainties for narrow-band features in HST/STIS whenusing linear basis models to account for the systematics. Our results furtherdemonstrate the use of ground-based multi-object spectrographs for the study ofexoplanet atmospheres, and highlight the need for caution in our interpretationof narrow-band features in low-resolution spectra of hot-Jupiters.

VLT/FORS2 comparative transmission spectroscopy II: confirmation of a cloud-deck and Rayleigh scattering in WASP-31b, but no potassium?