High-precision multiwavelength eclipse photometry of the ultra-hot gas giant exoplanet WASP-103 b

Abstract

We present sixteen occultation and three transit light curves for the ultra-short period hot Jupiter WASP-103b, in addition to five new radial velocity measurements. We combine these observations with archival data and perform a global analysis of the resulting extensive dataset, accounting for the contamination from a nearby star. We detect the thermal emission of the planet in both the z and K S -bands, the measured occultation depths being 699±110 ppm (6.4-σ) and 3567 +400 −350 ppm (10.2-σ), respectively. We use these two measurements together with recently published HST/WFC3 data to derive joint constraints on the properties of WASP-103b's dayside atmosphere. On one hand, we find that the z -band and WFC3 data are best fit by an isothermal atmosphere at 2900 K or an atmosphere with a low H 2 O abundance. On the other hand, we find an unexpected excess in the K S -band measured flux compared to these models, which requires confirmation with additional observations before any interpretation can be given. From our global data analysis, we also derive a broad-band optical transmission spectrum that shows a minimum around 700 nm and increasing values towards both shorter and longer wavelengths. This is in agreement with a previous study based on a large fraction of the archival transit light curves used in our analysis. The unusual profile of this transmission spectrum is poorly matched by theoretical spectra and is not confirmed by more recent observations at higher spectral resolution. Additional data, both in emission and transmission, are required to better constrain the atmospheric properties of WASP-103b.

Low albedos of hot to ultra-hot Jupiters in the optical to near-infrared transition regime

“…Generally, if the day side atmosphere is cloud-free at the probed pressure range and non-isothermal, we would expect to measure a wavelength-dependent brightness temperature due to spectral features. In this case, the z' band usually shows a larger eclipse depth and brightness temperature than the best-fit blackbody temperature (Delrez et al 2018, see also Fig. 5).…”

“…Because of a conservative upper limit on the albedo, we choose the lowest of 2890 K derived by Cartier et al (2017). The values of the planetary parameters involved in Equation 1 and 2 were taken from Delrez et al (2018). This results in a tight constraint of a 97.5% confidence upper limit of A g < 0.16, the lowest value derived in this work (see Table 4).…”

“…There are several literature reports of z' band secondary eclipse measurements for different planets (López-Morales et al 2010;Lendl et al 2013;Föhring et al 2013;Delrez et al 2016Delrez et al , 2018. These gas giants show equilibrium temperatures above 2500 K, hence they belong to the group of the so-called ultra-hot Jupiters.…”

Statistical Characterization of Hot Jupiter Atmospheres Using Spitzer’s Secondary Eclipses

“…Thus, we support their retrieved results for this planet. Our dilution correction is based on the K-magnitude difference from Ngo et al (2016) and Delrez et al (2018). WASP-121b was observed by Evans et al (2017) and Kovacs & Kovacs (2019) who quote 3.6 µm Spitzer secondary eclipse values.…”

Storms or systematics? The changing secondary eclipse depth of WASP-12b

“…Madhusudhan (2012) predicted that for many hot Jupiters, thermal emission measurements at these wavelengths are good discriminators between carbonrich and carbon-poor exoplanets. Whilst secondary eclipse observations conducted at z -band wavelengths have been published for 9 exoplanets 1 (Sing & López-Morales 2009;López-Morales et al 2010;Smith et al 2011;Burton et al 2012;Gillon et al 2012;Lendl et al 2013;Zhou et al 2013;Föhring et al 2013;Chen et al 2014;Delrez et al 2016;Gaudi et al 2017;Delrez et al 2018), only two studies have reported secondary eclipse observations at i -band wavelengths (Mancini et al 2013;Chen et al 2014), with the most confident detection reported at 3.7σ.…”