The HUSTLE Program: The UV to Near-Infrared HST WFC3/UVIS G280 Transmission Spectrum of WASP-127b

TL;DR

This study presents the ultraviolet to near-infrared transmission spectrum of exoplanet WASP-127b using HST WFC3/UVIS G280, revealing high-altitude clouds and tentative sodium detection, demonstrating the instrument's capability for atmospheric characterization.

Contribution

First ultraviolet-visible transmission spectrum of WASP-127b obtained with HST WFC3/UVIS G280, showing cloud properties and sodium detection enhancement with archival data.

Findings

Evidence for high-altitude, patchy clouds composed of sub-micron particles.

Weak sodium detection in UVIS data, strengthened to 4.1-sigma with archival data.

Demonstrates HST WFC3/UVIS G280's effectiveness in exoplanet atmospheric studies.

Abstract

Ultraviolet wavelengths offer unique insights into aerosols in exoplanetary atmospheres. However, only a handful of exoplanets have been observed in the ultraviolet to date. Here, we present the ultraviolet-visible transmission spectrum of the inflated hot Jupiter WASP-127b. We observed one transit of WASP-127b with WFC3/UVIS G280 as part of the Hubble Ultraviolet-optical Survey of Transiting Legacy Exoplanets (HUSTLE), obtaining a transmission spectrum from 200-800 nm. Our reductions yielded a broad-band transit depth precision of 91 ppm and a median precision of 240 ppm across 59 spectral channels. Our observations are suggestive of a high-altitude cloud layer with forward modeling showing they are composed of sub-micron particles and retrievals indicating a high opacity patchy cloud. While our UVIS/G280 data only offers weak evidence for Na, adding archival HST WFC3/IR and STIS observations raises the overall Na detection significance to 4.1-sigma. Our work demonstrates the capabilities of HST WFC3/UVIS G280 observations to probe the aerosols and atmospheric composition of transiting hot Jupiters with comparable precision to HST STIS.