WASP-77 Ab: A transiting hot Jupiter planet in a wide binary system

TL;DR

This paper reports the discovery and characterization of a transiting hot Jupiter in a wide binary system, analyzing its properties and host star activity to understand planetary formation and evolution in binary environments.

Contribution

The study presents the first detailed analysis of a hot Jupiter in a wide binary, combining photometric and spectroscopic data to determine planetary and stellar properties.

Findings

The planet has a mass of 1.76±0.06 MJup and a radius of 1.21±0.02 RJup.

The host star shows moderate chromospheric activity and photometric variability.

The system's age estimates vary significantly depending on the method used.

Abstract

We report the discovery of a transiting planet with an orbital period of 1.36d orbiting the brighter component of the visual binary star BD -07 436. The host star, WASP-77A, is a moderately bright G8V star (V=10.3) with a metallicity close to solar ([Fe/H]= 0.0 +- 0.1). The companion star, WASP-77B, is a K-dwarf approximately 2 magnitudes fainter at a separation of approximately 3arcsec. The spectrum of WASP-77A shows emission in the cores of the Ca II H and K lines indicative of moderate chromospheric activity. The WASP lightcurves show photometric variability with a period of 15.3 days and an amplitude of about 0.3% that is probably due to the magnetic activity of the host star. We use an analysis of the combined photometric and spectroscopic data to derive the mass and radius of the planet (1.76+-0.06MJup, 1.21+-0.02RJup). The age of WASP-77A estimated from its rotation rate (~1 Gyr) agrees with the age estimated in a similar way for WASP-77B (~0.6 Gyr) but is in poor agreement with the age inferred by comparing its effective temperature and density to stellar models (~8 Gyr). Follow-up observations of WASP-77 Ab will make a useful contribution to our understanding of the influence of binarity and host star activity on the properties of hot Jupiters.