2020/04/28 by Shreyas Vissapragada, Heather A. Knutson, Nemanja Jovanovic +7
Physics and Astronomy · #Absorption (acoustics) #Absorption spectroscopy #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Helium #Metastability #Photometry (optics) #Spectroscopy #Stellar, planetary, and galactic studies #Telescope #Wavelength #astro-ph.EP #astro-ph.IM
paper · pdf · doi:10.3847/1538-3881/ab8e34
17 pages, 8 figures (figures 1 and 2 are rasterized for arXiv file size compliance), accepted to AJ
arxiv created 2020/04/28 · openalex created_date 2020/05/13 · openalex publication_date 2020/05/27 · arxiv updated 2020/06/03 · openalex updated_date 2026/08/06
Abstract Infrared observations of metastable 2 3 S helium absorption with ground- and space-based spectroscopy are rapidly maturing, as this species is a unique probe of exoplanet atmospheres. Specifically, the transit depth in the triplet feature (with vacuum wavelengths near 1083.3 nm) can be used to constrain the temperature and mass-loss rate of an exoplanet’s upper atmosphere. Here, we present a new photometric technique to measure metastable 2 3 S helium absorption using an ultranarrowband filter (FWHM 0.635 nm) coupled to a beam-shaping diffuser installed in the Wide-field Infrared Camera on the 200 inch Hale Telescope at Palomar Observatory. We use telluric OH lines and a helium arc lamp to characterize refractive effects through the filter and to confirm our understanding of the filter transmission profile. We benchmark our new technique by observing a transit of WASP-69b and detect an excess absorption of 0.498% ± 0.045% (11.1 σ ), consistent with previous measurements after considering our bandpass. We then use this method to study the inflated gas giant WASP-52b and place a 95th percentile upper limit on excess absorption in our helium bandpass of 0.47%. Using an atmospheric escape model, we constrain the mass-loss rate for WASP-69b to be ( ) at 7000 K (12,000 K). Additionally, we set an upper limit on the mass-loss rate of WASP-52b at these temperatures of ( ). These results show that ultranarrowband photometry can reliably quantify absorption in the metastable helium feature.