2020AJ....159..115K

We present the detection of helium in the extended atmosphere of the sub-Saturn WASP-107b using high-resolution (R ≃ 25,000) near-infrared spectra from Keck II/Near Infrared Echelle Spectrograph (NIRSPEC). We find peak excess absorption of 7.26% ± 0.24% (30σ) centered on the He I triplet at 10833 Å. The amplitude and shape of the helium absorption profile is in excellent agreement with previous observations of escaping helium from this planet made by CARMENES and the Hubble Space Telescope. This suggests there is no significant temporal variation in the signature of escaping helium from the planet over a two year baseline. This result demonstrates Keck II/NIRSPEC's ability to detect atmospheric escape in exoplanets, making it a useful instrument to further our understanding of the evaporation of exoplanetary atmospheres via ground-based observations of He I.