# Starspots on WASP-107 and pulsations of WASP-118

## TL;DR

This study analyzes K2 photometry of WASP-107 and WASP-118, detecting starspot occultations, stellar pulsations, and refining system parameters, while also setting limits on planetary albedos and searching for additional planets.

## Contribution

It reports the first detection of starspot occultations on WASP-107 and identifies gamma Doradus pulsations in WASP-118, providing new insights into stellar activity and system characterization.

## Key findings

- Starspot occultations detected on WASP-107.
- Gamma Doradus pulsations observed in WASP-118.
- No transit-timing variations or additional planets found.

## Abstract

By analysing the K2 short-cadence photometry we detect starspot occultation events in the lightcurve of WASP-107, the host star of a warm-Saturn exoplanet. WASP-107 also shows a rotational modulation with a period of 17.5 +/- 1.4 d. Given that the rotational period is nearly three times the planet's orbital period, one would expect in an aligned system to see starspot occultation events to recur every three transits. The absence of such occultation recurrences suggests a misaligned orbit unless the starspots' lifetimes are shorter than the star's rotational period. We also find stellar variability resembling gamma Doradus pulsations in the lightcurve of WASP-118, which hosts an inflated hot Jupiter. The variability is multi-periodic with a variable semi-amplitude of about 200 ppm. In addition to these findings we use the K2 data to refine the parameters of both systems, and report non-detections of transit-timing variations, secondary eclipses and any additional transiting planets. We used the upper limits on the secondary-eclipse depths to estimate upper limits on the planetary geometric albedos of 0.7 for WASP-107b and 0.2 for WASP-118b.