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Published June 2020 | Accepted Version + Published
Journal Article Open

Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultranarrowband Photometry


Infrared observations of metastable 2³S 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 23S 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% (11.1σ), 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 5.25^(+0.65)_(−0.46) × 10⁻⁴ M_J/Gyr⁻¹ (3.32^(+0.67)_(−0.56) × 10⁻³ M_J/Gyr⁻¹) at 7000 K (12,000 K). Additionally, we set an upper limit on the mass-loss rate of WASP-52b at these temperatures of 2.1 × 10⁻⁴ M_J/Gyr⁻¹ (2.1×10⁻³ M_J/Gyr⁻¹) . These results show that ultranarrowband photometry can reliably quantify absorption in the metastable helium feature.

Additional Information

© 2020 The American Astronomical Society. Received 2020 February 4; revised 2020 April 24; accepted 2020 April 27; published 2020 May 28. We thank the referee for a very thorough review that improved the quality of this work. We are grateful for the support of the Heising-Simons Foundation, which allowed us to purchase the narrowband filter used in this study. We thank Lisa Nortmann for providing us with the CARMENES data for WASP-69b. We recognize the Palomar Observatory staff for their support of our work, especially Paul Nied and Kajse Peffer for telescope operation and James Brugger, Greg Van Idsinga, Ernie Velador, and Brian Faull for assistance with helium lamp hardware. We also thank James Owen, Yanqin Wu, Trevor David, Ignas Snellen, Yayaati Chachan, Fei Dai, Munazza Alam, Nikolay Nikolov, Chaz Shapiro, Jennifer Milburn, Andy Boden, Roger Smith, and Keith Matthews for very useful conversations. S.V. is supported by an NSF Graduate Research Fellowship and the Paul & Daisy Soros Fellowship for New Americans. H.A.K. acknowledges support from NSF CAREER grant 1555095 and NASA Origins grant NNX14AD22G. C.K.H. acknowledges support from the University of Maryland Department of Astronomy Honors Program, and from the Smithsonian Astrophysical Observatory REU program, which is funded in part by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant no. AST-1852268, and by the Smithsonian Institution. A.O. acknowledges support by NASA through the NASA Hubble Fellowship grant HST-HF2-51443.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. Facilities: Hale (WIRC) - , ADS - , Exoplanet Archive. - Software: photutils (Bradley et al. 2016), numpy (van der Walt et al. 2011), astropy (Astropy Collaboration et al. 2013, 2018), scipy (Virtanen et al. 2019), matplotlib (Hunter 2007), batman (Kreidberg 2015), emcee (Foreman-Mackey et al. 2013), corner (Foreman-Mackey 2016), ldtk (Husser et al. 2013; Parviainen & Aigrain 2015), Aladin Lite (Bonnarel et al. 2000; Boch & Fernique 2014).

Attached Files

Published - Vissapragada_2020_AJ_159_278.pdf

Accepted Version - 2004.13728.pdf


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August 22, 2023
February 2, 2024