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

**Authors:** T. Močnik, C. Hellier, D. R. Anderson, B. J. M. Clark, J. Southworth  
**arXiv:** [1702.05078](https://arxiv.org/abs/1702.05078)  
**Date:** 2017-02-16  
**Summary page:** https://www.summarizepaper.com/en/paper/1702.05078v2/

## Key points

- Researchers analyzed K2 short-cadence photometry to study starspot occultation events in the lightcurve of WASP-107, the host star of a warm-Saturn exoplanet.
- WASP-107 exhibited rotational modulation with a period of 17.5 +/- 1.4 days, suggesting a misaligned orbit or shorter lifetimes for starspots.
- Stellar variability resembling gamma Doradus pulsations was discovered in the lightcurve of WASP-118, which hosts an inflated hot Jupiter.
- The variability displayed multi-periodic behavior with a variable semi-amplitude of approximately 200 ppm.
- Parameters of both systems were refined and non-detections of transit-timing variations, secondary eclipses, and additional transiting planets were reported.
- Upper limits on secondary eclipse depths were used to estimate upper limits on planetary geometric albedos: 0.7 for WASP-107b and 0.2 for WASP-118b.
- Valuable insights into starspot occultation events and stellar variability in exoplanetary systems have been provided through this study, refining our understanding of these celestial objects.

## Summary

In a recent study, researchers analyzed the K2 short-cadence photometry to investigate starspot occultation events in the lightcurve of WASP-107, the host star of a warm-Saturn exoplanet. They observed that WASP-107 also exhibited a rotational modulation with a period of 17.5 +/- 1.4 days, which was nearly three times the planet's orbital period. This suggests either a misaligned orbit or shorter lifetimes for the starspots compared to the star's rotational period, as no recurrences were observed every three transits. Additionally, the team discovered stellar variability resembling gamma Doradus pulsations in the lightcurve of WASP-118, which hosts an inflated hot Jupiter. This variability displayed multi-periodic behavior with a variable semi-amplitude of approximately 200 ppm. Using this data, they refined parameters of both systems and reported non-detections of transit-timing variations, secondary eclipses and any additional transiting planets. The upper limits on secondary eclipse depths were used to estimate upper limits on planetary geometric albedos: 0.7 for WASP-107b and 0.2 for WASP-118b. Through this study, valuable insights into starspot occultation events and stellar variability in exoplanetary systems have been provided while refining our understanding of these celestial objects.