1. HST PanCET Program: A Complete Near-UV to Infrared Transmission Spectrum for the Hot Jupiter WASP-79b
- Author
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Lars A. Buchhave, Jorge Sanz-Forcada, Munazza K. Alam, Jayesh M. Goyal, Joanna K. Barstow, David K. Sing, João M. Mendonça, Nikolay Nikolov, Katy L. Chubb, Alexander D. Rathcke, Jake Taylor, Mercedes Lopez-Morales, Gregory W. Henry, Nikole K. Lewis, Ryan J. MacDonald, University of St Andrews. School of Physics and Astronomy, Rathcke, A. D. [0000-0002-4227-4953], MacDonald, R. J. [0000-0003-4816-3469], Barstow, J. K. [0000-0003-3726-5419], Goyal, J. M. [0000-0002-8515-7204], López Morales, M. [0000-0003-3204-8183], Mendoça, J. M. [0000-0002-6907-4476], Sanz Forcada, J. [0000-0002-1600-7835], Henry, G. W. [0000-0003-4155-8513], Sing, D. K. [0000-0001-6050-7645], Alam, M. K. [0000-0003-4157-832X], Lewis, N. K. [0000-0002-8507-1304], Chubb, K. L. [0000-0002-4552-4559], Taylor, J. [0000-0003-4844-9838], Nikolov, N. [0000-0002-6500-3574], Buchhave, L. A. [0000-0003-1605-5666], and Agencia Estatal de Investigación (AEI)
- Subjects
Opacity ,Metallicity ,Hot Jupiters ,NDAS ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Neptune-mass exoplanet ,Absorption ,Atmosphere ,Observational astronomy ,Hot Jupiter ,Transmission spectroscopy ,Giant planets ,QB Astronomy ,Astrophysics::Solar and Stellar Astrophysics ,Transit (astronomy) ,Gaussian process framework ,Spectroscopy ,QC ,Astrophysics::Galaxy Astrophysics ,QB ,Physics ,Earth and Planetary Astrophysics (astro-ph.EP) ,Photosphere ,Retrieval ,James Webb Space Telescope ,Astronomy and Astrophysics ,QC Physics ,Space and Planetary Science ,HD 189733B ,Exoplanets atmospheric composition ,Molecular line lists ,Astrophysics::Earth and Planetary Astrophysics ,Hubble ,Exoplanet atmospheres ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We present a new optical transmission spectrum of the hot Jupiter WASP-79b. We observed three transits with the STIS instrument mounted on HST, spanning 0.3 - 1.0 um. Combining these transits with previous observations, we construct a complete 0.3 - 5.0 um transmission spectrum of WASP-79b. Both HST and ground-based observations show decreasing transit depths towards blue wavelengths, contrary to expectations from Rayleigh scattering or hazes. We infer atmospheric and stellar properties from the full near-UV to infrared transmission spectrum of WASP-79b using three independent retrieval codes, all of which yield consistent results. Our retrievals confirm previous detections of H$_{2}$O (at 4.0$\sigma$ confidence), while providing moderate evidence of H$^{-}$ bound-free opacity (3.3$\sigma$) and strong evidence of stellar contamination from unocculted faculae (4.7$\sigma$). The retrieved H$_{2}$O abundance ($\sim$ 1$\%$) suggests a super-stellar atmospheric metallicity, though stellar or sub-stellar abundances remain consistent with present observations (O/H = 0.3 - 34$\times$ stellar). All three retrieval codes obtain a precise H$^{-}$ abundance constraint: log(X$_{\rm{H^{-}}}$) $\approx$ -8.0 $\pm$ 0.7. The potential presence of H$^{-}$ suggests that JWST observations may be sensitive to ionic chemistry in the atmosphere of WASP-79b. The inferred faculae are $\sim$ 500 K hotter than the stellar photosphere, covering $\sim$ 15$\%$ of the stellar surface. Our analysis underscores the importance of observing UV - optical transmission spectra in order to disentangle the influence of unocculted stellar heterogeneities from planetary transmission spectra., Comment: 27 pages, 10 figures. Resubmitted to AJ after referee report
- Published
- 2021
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