The ultra-hot-Jupiter KELT-16 b: Dynamical Evolution and Atmospheric Properties

TL;DR

This study provides precise measurements of the ultra-hot Jupiter KELT-16b's physical and atmospheric properties, including transit timings, atmospheric composition, and phase curve analysis, with no evidence of orbital decay over four years.

Contribution

It offers the most precise physical and atmospheric characterization of KELT-16b to date, including transit timing, atmospheric composition, and phase curve analysis, with constraints on orbital decay.

Findings

No evidence of orbital period change over four years.

Detected optical absorbers in the atmosphere with low significance.

Evidence of a temperature inversion and oxygen-rich atmosphere.

Abstract

We present broad-band photometry of 30 planetary transits of the ultra-hot Jupiter KELT-16b, using five medium-class telescopes. The transits were monitored through standard B, V, R, I filters and four were simultaneously observed from different places, for a total of 36 new light curves. We used these new photometric data and those from the TESS space telescope to review the main physical properties of the KELT-16 planetary system. Our results agree with previous measurements but are more precise. We estimated the mid-transit times for each of these transits and combined them with others from the literature to obtain 69 epochs, with a time baseline extending over more than four years, and searched for transit time variations. We found no evidence for a period change, suggesting a lower limit for orbital decay at 8 Myr, with a lower limit on the reduced tidal quality factor of $Q^{\prime}_{\star}>(1.9 \pm 0.8) \times 10^5$ with $95\%$ confidence. We built up an observational, low-resolution transmission spectrum of the planet, finding evidence of the presence of optical absorbers, although with a low significance. Using TESS data, we reconstructed the phase curve finding that KELT-16b has a phase offset of $25.25 \pm 14.03$ $^{\circ}$E, a day- and night-side brightness temperature of $3190 \pm 61$ K and $2668 \pm 56$ K, respectively. Finally, we compared the flux ratio of the planet over its star at the TESS and Spitzer wavelengths with theoretical emission spectra, finding evidence of a temperature inversion in the planet's atmosphere, the chemical composition of which is preferably oxygen-rich rather than carbon-rich.