The Keck Planet Finder SURFS-UP Survey. I. Transmission Spectroscopy of WASP-76 b

July 2026 • 2026AJ....172...48H

Authors • Householder, Aaron • Dai, Fei • Kesseli, Aurora • Howard, Andrew W. • Halverson, Samuel • Fulton, Benjamin J. • Zhang, Yapeng • Polanski, Alex S. • Inglis, Julie • Tusay, Nick • Bello-Arufe, Aaron • Baker, Ashley D. • Burdge, Kevin B. • Edelstein, Jerry • Giacalone, Steven • Gibson, Steven R. • Gilbert, Gregory J. • Handley, Luke B. • Isaacson, Howard • Laher, Russ R. • Petigura, Erik A. • Rider, Kodi • Roy, Arpita • Rubenzahl, Ryan A. • Smith, Chris • Vanderburg, Andrew • Walawender, Josh • Weiss, Lauren M.

Abstract • We introduce the Keck Planet Finder (KPF) Spectroscopy of the Upper Atmospheres and Refractory Species in Ultrahot Planets (SURFS-UP) Survey, a high-resolution survey to investigate the atmospheric composition and dynamics of a sample of ultrahot Jupiters with the KPF. Due to the unique design of KPF, we developed a publicly available pipeline for KPF that performs blaze removal, continuum normalization, order stitching, science spectra combination, telluric correction, and atmospheric detection via cross correlation. As a first demonstration, we applied this pipeline to a transit of WASP-76 b and achieved some of the highest signal-to-noise ratio (SNR) detections of refractory species in WASP-76 b to date (e.g., Fe I is detected at an SNR of 14.5). We confirm previous observations of an asymmetry in Fe I absorption, but find no measurable ingress─egress asymmetry in Na I and Ca II. Together, these results suggest variations within different layers of the atmosphere of WASP-76 b: neutral metals such as Fe I trace deeper regions with stronger asymmetries, while Na I and Ca II probe regions higher in the atmosphere where the ingress─egress asymmetries are weaker. Unlike some other ultrahot Jupiters, our results are qualitatively consistent with general circulation model predictions of decreasing velocity asymmetry with altitude and do not require a high-altitude superrotating jet that has been invoked for other planets (e.g., WASP-121 b). These results suggest that atmospheric circulation patterns in ultrahot Jupiters may be more diverse than previously thought, highlighting the need for broader surveys to study how atmospheric dynamics depend on planetary and stellar properties.

Links

• ELECTR https://doi.org/10.3847/1538-3881/ae71b9