Larger and faster: revised properties and a shorter orbital period for the WASP-57 planetary system from a pro-am collaboration

TL;DR

This study refines the orbital and physical properties of the WASP-57 planetary system using combined amateur and professional observations, revealing a shorter orbital period and larger, less massive star and planet, with implications for atmospheric characterization.

Contribution

The paper presents a revised orbital period and physical parameters for WASP-57 based on extensive multi-source transit data, demonstrating the value of pro-am collaboration in exoplanet research.

Findings

Orbital period shorter by 4.5 seconds than previous estimate.

Star and planet are larger and less massive than earlier measurements.

Transit observations across multiple wavelengths provide insights into atmospheric properties.

Abstract

Transits in the WASP-57 planetary system have been found to occur half an hour earlier than expected. We present ten transit light curves from amateur telescopes, on which this discovery was based, thirteen transit light curves from professional facilities which confirm and refine this finding, and high-resolution imaging which show no evidence for nearby companions. We use these data to determine a new and precise orbital ephemeris, and measure the physical properties of the system. Our revised orbital period is 4.5s shorter than found from the discovery data alone, which explains the early occurrence of the transits. We also find both the star and planet to be larger and less massive than previously thought. The measured mass and radius of the planet are now consistent with theoretical models of gas giants containing no heavy-element core, as expected for the sub-solar metallicity of the host star. Two transits were observed simultaneously in four passbands. We use the resulting light curves to measure the planet's radius as a function of wavelength, finding that our data are sufficient in principle but not in practise to constrain its atmospheric properties. We conclude with a discussion of the current and future status of transmission photometry studies for probing the atmospheres of gas-giant transiting planets.