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 a dimensionless index that quantifies the degree of cloudiness ofthe atmosphere of a transiting exoplanet. Our cloudiness index is based onmeasuring the transit radii associated with the line center and wing of thesodium or potassium line. In deriving this index, we revisited the algebraicformulae for inferring the isothermal pressure scale height from transitmeasurements. We demonstrate that the formulae of Lecavelier et al. and Benneke& Seager are identical: the former is inferring the temperature while assuminga value for the mean molecular mass and the latter is inferring the meanmolecular mass while assuming a value for the temperature. More importantly,these formulae cannot be used to distinguish between cloudy and cloudfreeatmospheres. We derive values of our cloudiness index for a small sample of 7hot Saturns/Jupiters taken from Sing et al. We show that WASP-17b, WASP-31b andHAT-P-1b are nearly cloudfree at visible wavelengths. We find the tentativetrend that more irradiated atmospheres tend to have less clouds consisting ofsub-micron-sized particles. We also derive absolute sodium and/or potassiumabundances $\sim 10^2$ cm$^{-3}$ for WASP-17b, WASP-31b and HAT-P-1b (and upperlimits for the other objects). Higher-resolution measurements of both thesodium and potassium lines, for a larger sample of exoplanetary atmospheres,are needed to confirm or refute this trend.

the astrophysical journal. letters

A Cloudiness Index for Transiting Exoplanets Based on the Sodium and  Potassium Lines: Tentative Evidence for Hotter Atmospheres Being Less Cloudy  at Visible Wavelengths