CSI papers published: ultra-hot Jupiter WASP-121b

An optical transmission spectrum for the ultra-hot Jupiter WASP-121b measured with the Hubble Space Telescope

An optical transmission spectrum for the ultra-hot Jupiter WASP-121b measured with the Hubble Space Telescope by T.M. Evans, CSI Member Nikole Lewis, and colleagues, email: nikole.lewis@cornell.edu

We present an atmospheric transmission spectrum for the ultra-hot Jupiter WASP-121b, measured using the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (HST). Across the 0.47 1 µm wavelength range, the data imply an atmospheric opacity comparable to - and in some spectroscopic channels exceeding - that previously measured at near-infrared wavelengths (1.15-1.65 µm).  Wavelength-dependent variations in the opacity rule out a gray cloud deck at a confidence level of 3.8σ and may instead be explained by VO spectral bands. We find a cloud-free model assuming chemical equilibrium for a temperature of 1500K and metal enrichment of 10-30x solar matches these data well. Using a free-chemistry retrieval analysis, we estimate a VO abundance of -6.6+0.2/-0.3 dex. We find no no evidence for TiO and place a 3σ upper limit of -7.9 dex on its abundance, suggesting TiO may have condensed from the gas phase at the day-night limb. The opacity rises steeply at the shortest wavelengths, increasing by approximately ve pressure scale heights from 0.47 to 0.3 µm in wavelength. If this feature is caused by Rayleigh scattering due to uniformly-distributed aerosols, it would imply an unphysically high temperature of 6810±1530 K. One alternative explanation for the short-wavelength rise is absorption due to SH (mercapto radical), which has been predicted as an important product of non-equilibrium chemistry in hot Jupiter atmospheres. Irrespective of the identity of the NUV absorber, it likely captures a significant amount of incident stellar radiation at low pressures, thus playing a significant role in the overall energy budget, thermal structure, and circulation of the atmosphere.

Nikole Lewis, Astronomy & Planetary Science

Klarman Hall at sunset

Tweets from CSInst

is an annual twitter competition hosted by to determine the most popular exoplanet of the year.… https://t.co/IgYMfPedoH
1 day 15 hours ago
We endorse , the 1st close-in planet found around a white dwarf, for ! To learn more about the… https://t.co/tX63gdObmU
1 day 16 hours ago
RT : So proud to hear the 100th episode of ! Thank you for bringing our to the local… https://t.co/naRcsnpdSB
2 days 12 hours ago
RT : Learn skills ! is offered online & open to everyone! Build a comm strategy,create… https://t.co/2vOy0egObM
2 days 14 hours ago
RT : Is there beyond ? "I think the numbers are forever in our favor," says of &… https://t.co/5VOEFUwRav
3 days 20 hours ago
Happy Thanksgiving to our American colleagues & followers. This year’s parade in NYC included a https://t.co/AMzaF6lKIo
3 days 21 hours ago