Near-infrared and optical emission of WASP-5 b^★

¹ Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Eötvös Loránd Research Network Budapest, Hungary
e-mail: kovacs@konkoly.hu
² Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Germany
³ Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, PR China
⁴ Center for Astrophysics, Harvard & Smithsonian, Cambridge, MA, USA
⁵ Centre for Astrophysics, University of Southern Queensland, Toowoomba, Australia
⁶ Departamento de Matemática y Física Aplicadas, Facultad de Ingeniería, Universidad Católica de la Santísima Concepción, Concepción, Chile
⁷ Institute of Physics, Faculty of Science, Eötvös Loránd University, Budapest, Hungary
⁸ School of Physics, University of New South Wales, Sydney, Australia

Received: 17 January 2022
Accepted: 20 April 2022

Abstract

Context. Thermal emission from extrasolar planets makes it possible to study important physical processes in their atmospheres and derive more precise orbital elements.

Aims. By using new near-infrared (NIR) and optical data, we examine how these data constrain the orbital eccentricity and the thermal properties of the planet atmosphere.

Methods. The full light curves acquired by the TESS satellite from two sectors are used to put an upper limit on the amplitude of the phase variation of the planet and estimate the occultation depth. Two previously published observations and one followup observation (published herein) in the 2MASS K (Ks) band are employed to derive a more precise occultation light curve in this NIR waveband.

Results. The merged occultation light curve in the Ks band comprises 4515 data points. The data confirm the results of the earlier eccentricity estimates, suggesting a circular orbit of: e = 0.005 ± 0.015. The high value of the flux depression of (2.70 ± 0.14) ppt in the Ks band excludes simple black body emission at the 10σ level and also disagrees with current atmospheric models at the (4–7)σ level. From analysis of the TESS data, in the visual band we find tentative evidence for a near-noise-level detection of the secondary eclipse, and place constraints on the associated amplitude of the phase variation of the planet. A formal box fit yields an occultation depth of (0.157 ± 0.056) ppt. This implies a relatively high geometric albedo of A_g = 0.43 ± 0.15 for fully efficient atmospheric circulation and A_g = 0.29 ± 0.15 for no circulation at all. No preference can be seen for either the oxygen-enhanced or the carbon-enhanced atmosphere models.