Examinando por Autor "MacDonald, R. J."

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Acceso Abierto
Evidence of a Clear Atmosphere for WASP-62b: The Only Known Transiting Gas Giant in the JWST Continuous Viewing Zone
(IOP Science Publishing, 2021-01-11) Alam, M. K.; López Morales, M.; MacDonald, R. J.; Nikolov, N.; Kirk, J.; Goyal, J. M.; Sing, D. K.; Wakeford, H. R.; Rathcke, A. D.; Deming, D. L.; Sanz Forcada, J.; Lewis, N. K.; Barstow, J. K.; Mikal Evans, T.; Buchhave, L. A.; National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Agencia Estatal de Investigación (AEI); Alam, M. K. [0000-0003-4157-832X]; López Morales, M. [0000-0003-3204-8183]; MacDonald, R. J. [0000-0003-4816-3469]; Nikolov, N. [0000-0002-6500-3574]; Kirk, J. [0000-0002-4207-6615]; Goyal, J. M. [0000-0002-8515-7204]; Sing, D. K. [0000-0001-6050-7645]; Wakeford, H. R. [0000-0003-4328-3867]; Rathcke, A. D. [0000-0002-4227-4953]; Deming, D. L. [0000-0001-5727-4094]; Sanz Forcada, J. [0000-0002-1600-7835]; Lewis, N. K. [0000-0002-8507-1304]; Barstow, J. K. [0000-0003-3726-5419]; Mikal Evans, T. [0000-0001-5442-1300]; Buchhave, L. A. [0000-0003-1605-5666]
Exoplanets with cloud-free, haze-free atmospheres at the pressures probed by transmission spectroscopy represent a valuable opportunity for detailed atmospheric characterization and precise chemical abundance constraints. We present the first optical to infrared (0.3−5 μm) transmission spectrum of the hot Jupiter WASP-62b, measured with Hubble/STIS and Spitzer/IRAC. The spectrum is characterized by a 5.1σ detection of Na i absorption at 0.59 μm, in which the pressure-broadened wings of the Na D-lines are observed from space for the first time. A spectral feature at 0.4 μm is tentatively attributed to SiH at 2.1σ confidence. Our retrieval analyses are consistent with a cloud-free atmosphere without significant contamination from stellar heterogeneities. We simulate James Webb Space Telescope (JWST) observations, for a combination of instrument modes, to assess the atmospheric characterization potential of WASP-62b. We demonstrate that JWST can conclusively detect Na, H2O, FeH, NH3, CO, CO2, CH4, and SiH within the scope of its Early Release Science (ERS) program. As the only transiting giant planet currently known in the JWST Continuous Viewing Zone, WASP-62b could prove a benchmark giant exoplanet for detailed atmospheric characterization in the James Webb era.
Acceso Abierto
HST PanCET Program: A Complete Near-UV to Infrared Transmission Spectrum for the Hot Jupiter WASP-79b
(IOP Science Publishing, 2021-09-10) Rathcke, A. D.; MacDonald, R. J.; Barstow, J. K.; Goyal, J. M.; López Morales, M.; Mendoça, J. M.; Sanz Forcada, J.; Henry, G. W.; Sing, D. K.; Alam, M. K.; Agencia Estatal de Investigación (AEI); 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]
We present a new optical transmission spectrum of the hot Jupiter WASP-79b. We observed three transits with the STIS instrument mounted on the Hubble Space Telescope (HST), spanning 0.3–1.0 μm. Combining these transits with previous observations, we construct a complete 0.3–5.0 μm transmission spectrum of WASP-79b. Both HST and ground-based observations show decreasing transit depths toward 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 H2O (at 4.0σ confidence) while providing moderate evidence of H− bound–free opacity (3.3σ) and strong evidence of stellar contamination from unocculted faculae (4.7σ). The retrieved H2O abundance (∼1%) suggests a superstellar atmospheric metallicity, though stellar or substellar abundances remain consistent with present observations (O/H = 0.3–34× stellar). All three retrieval codes obtain a precise H− abundance constraint: log(${X}_{{{\rm{H}}}^{-}}$) ≈ −8.0 ± 0.7. The potential presence of H− suggests that James Webb Space Telescope observations may be sensitive to ionic chemistry in the atmosphere of WASP-79b. The inferred faculae are ∼500 K hotter than the stellar photosphere, covering ∼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.