Thermal emission of WASP-48b in the K_s-band^★

¹ Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
e-mail: b.j.clark@keele.ac.uk
² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
³ N. Copernicus Astronomical Centre, Polish Academy of Sciences, Bartycka 18, 00-716 Warsaw, Poland
⁴ Institute of Planetary Research, German Aerospace Center, Rutherfordstrasse 2, 12489 Berlin, Germany
⁵ SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, Fife KY16 9SS, UK

Received: 28 July 2015
Accepted: 22 March 2018

Abstract

We report a detection of thermal emission from the hot Jupiter WASP-48b in the K_s-band. We used the Wide-field Infra-red Camera on the 3.6-m Canada-France Hawaii Telescope to observe an occultation of the planet by its host star. From the resulting occultation lightcurve we find a planet-to-star contrast ratio in the K_s-band of 0.136 ± 0.014%, in agreement with the value of 0.109 ± 0.027% previously determined. We fit the two K_s-band occultation lightcurves simultaneously with occultation lightcurves in the H-band and the Spitzer 3.6- and 4.5-μm bandpasses, radial velocity data, and transit lightcurves. From this, we revise the system parameters and construct the spectral energy distribution (SED) of the dayside atmosphere. By comparing the SED with atmospheric models, we find that both models with and without a thermal inversion are consistent with the data. We find the planet’s orbit to be consistent with circular (e < 0.072 at 3σ).