A High Geometric Albedo for LTT9779b Points Towards a Metal-rich Atmosphere and Silicate Clouds

Abstract

Aims: In this work, we aim to confirm the high albedo of the benchmark ultrahot Neptune LTT9779b using 20 secondary eclipse measurements of the planet observed with CHEOPS. In addition, we perform a search for variability in the reflected light intensity of the planet as a function of time. Methods: First, we used the TESS follow-up data of LTT9779b from three sectors (2, 29, and 69) to remodel the transit signature and estimate an updated set of transit and ephemeris parameters, which were directly used in the modeling of the secondary eclipse lightcurves. This involved a critical noise-treatment algorithm, including sophisticated techniques such as wavelet denoising and Gaussian Process (GP) regression, to constrain noise levels from various sources. In addition to using the officially released reduced aperture photometry data from CHEOPS DRP, we also reduced the raw data using an independent PSF photometry pipeline, known as PIPE, to verify the robustness of our analysis. The extracted secondary eclipse lightcurves were modeled using the PYCHEOPS package, where we have detrended the background noise correlated with the spacecraft roll angle, originating from the inhomogeneous and asymmetric shape of the CHEOPS point spread function, using an N-order glint function. Results: Our independent lightcurve analyses have resulted in consistent estimations of the eclipse depths, with values of 89.9$\pm$13.7 ppm for the DRP analysis and 85.2$\pm$13.1 ppm from PIPE, indicating a high degree of statistical agreement. Adopting the DRP value yields a highly constrained geometric albedo of 0.73$\pm$0.11. No significant eclipse depth variability is detected down to a level of $\sim$37 ppm. Conclusions: Our results confirm that LTT9779b exhibits a strikingly high optical albedo, which substantially reduces the internal energy budget of the planet compared to more opaque...

18 pages, 11 figures, 3 tables, Accepted for publication in A&A

References in corpus (23)

• The Transiting Exoplanet Survey Satellite
• The CHEOPS mission
• The Very Low Albedo of an Extrasolar Planet: MOST Spacebased Photometry of HD 209458
• Changing Phases of Alien Worlds: Probing Atmospheres of Kepler Planets with High-Precision Photometry
• A solar C/O and sub-solar metallicity in a hot Jupiter atmosphere
• A broadband thermal emission spectrum of the ultra-hot Jupiter WASP-18b
• An Ultra-Hot Neptune in the Neptune desert
• A unique hot Jupiter spectral sequence with evidence for compositional diversity
• Analysis of Early Science observations with the CHaracterising ExOPlanets Satellite (CHEOPS) using pycheops
• CHEOPS geometric albedo of the hot Jupiter HD 209458b
• Phase Curves of Hot Neptune LTT 9779b Suggest a High-Metallicity Atmosphere
• Hot Jupiter Diversity and the Onset of TiO/VO Revealed by a Large Grid of Non-Grey Global Circulation Models
• The geometric albedo of the hot Jupiter HD 189733b measured with CHEOPS
• Spitzer Reveals Evidence of Molecular Absorption in the Atmosphere of the Hot Neptune LTT 9979b
• Average Albedos of Close-in Super-Earths and Neptunes from Statistical Analysis of Long Cadence Kepler Secondary Eclipse Data
• Multi-band transit follow up observations of five hot-Jupiters with critical noise treatments: Improved physical properties
• The HD 93963 A transiting system: A 1.04d super-Earth and a 3.65 d sub-Neptune discovered by TESS and CHEOPS
• Critical Analysis of TESS Transit Photometric Data: Improved Physical Properties for Five Exoplanets
• A closer look at LTT 9779b: The ESPRESSO endeavour to pierce the atmospheric veil
• Knot a Bad Idea: Testing BLISS Mapping for Spitzer Space Telescope Photometry
• Precise Transit Photometry Using TESS II: Revisiting 28 Additional Transiting Systems With Updated Physical Properties
• Precise Transit Photometry Using TESS: Updated Physical Properties for 28 Exoplanets Around Bright Stars
• Lessons from Hubble and Spitzer: 1D Self-Consistent Model Grids for 19 Hot Jupiter Emission Spectra

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• TOI-333b: A Neptune Desert planet around a F7V star