Astron. J., 159, 278-278 (2020/June-0)
Constraints on metastable helium in the atmospheres of WASP-69b and WASP-52b with ultranarrowband photometry.
VISSAPRAGADA S., KNUTSON H.A., JOVANOVIC N., HARADA C.K., OKLOPCIC A., ERIKSEN J., MAWET D., MILLAR-BLANCHAER M.A., TINYANONT S. and VASISHT G.
Abstract (from CDS):
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 5.25–0.46+0.65×10–4MJGyr–1 (3.32–0.56+0.67×10–3MJGyr–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 2.1×10–4MJGyr–1 (2.1×10–3MJGyr–1). These results show that ultranarrowband photometry can reliably quantify absorption in the metastable helium feature.
© 2020. The American Astronomical Society. All rights reserved.
Exoplanet astronomy - Exoplanet atmospheres - Planetary atmospheres - Transmission spectroscopy - Infrared photometry - Narrow band photometry
VizieR on-line data:
<Available at CDS (J/AJ/159/278): fig1.dat fig4a.dat fig4b.dat>
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