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 ^ { \prime } and K _ { \mathrm { S } } -bands , the measured occultation depths being 699 \pm 110 ppm ( 6.4- \sigma ) and 3567 _ { -350 } ^ { +400 } ppm ( 10.2- \sigma ) , 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 ^ { \prime } -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 _ { \mathrm { 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 .