WASP-104b is Darker than Charcoal

TL;DR

This study analyzes K2 data of WASP-104b, revealing it to be extremely dark with very low reflectivity, and provides refined system parameters while detecting stellar and planetary modulations.

Contribution

It presents the first detection of phase-curve modulation in WASP-104 and establishes its very low geometric albedo, advancing understanding of hot-Jupiter atmospheres.

Findings

Detected high-significance ellipsoidal modulation

Established geometric albedo below 0.03 at 95% confidence

Refined system parameters and constrained additional signals

Abstract

By analysing the K2 short-cadence data from Campaign 14 we detect phase-curve modulation in the light curve of the hot-Jupiter host star WASP-104. The ellipsoidal modulation is detected with high significance and in agreement with theoretical expectations, while Doppler beaming and reflection modulations are detected tentatively. We show that the visual geometric albedo is lower than 0.03 at 95% confidence, making it one of the least-reflective planets found to date. The light curve also exhibits a rotational modulation, implying a stellar rotational period likely to be near 23 or 46 days. In addition, we refine the system parameters and place tight upper limits for transit timing and duration variations, starspot occultation events, and additional transiting planets.