Hot Jupiters with relatives: discovery of additional planets in orbit around WASP-41 and WASP-47

TL;DR

This paper reports the discovery of two additional long-period planets orbiting stars with hot Jupiters, providing insights into planetary system architectures and stellar activity effects on radial velocity measurements.

Contribution

It presents the detection of new planetary companions to WASP-41 and WASP-47, highlighting systems with hot Jupiters and long-period planets at about 1 au, and analyzes stellar activity and planetary alignment.

Findings

WASP-41 c has a mass of 3.18 M_Jup, eccentricity 0.29, orbiting in 421 days.

WASP-47 c has a mass of 1.24 M_Jup, eccentricity 0.13, orbiting in 572 days.

WASP-41's stellar activity cycle can be tracked using Hα emission.

Abstract

We report the discovery of two additional planetary companions to WASP-41 and WASP-47. WASP-41 c is a planet of minimum mass 3.18 $\pm$ 0.20 M$_{\rm Jup}$ and eccentricity 0.29 $\pm$ 0.02, and it orbits in 421 $\pm$ 2 days. WASP-47 c is a planet of minimum mass 1.24 $\pm$ 0.22 M$_{\rm Jup}$ and eccentricity 0.13 $\pm$ 0.10, and it orbits in 572 $\pm$ 7 days. Unlike most of the planetary systems that include a hot Jupiter, these two systems with a hot Jupiter have a long-period planet located at only $\sim$1 au from their host star. WASP-41 is a rather young star known to be chromospherically active. To differentiate its magnetic cycle from the radial velocity effect induced by the second planet, we used the emission in the H$\alpha$ line and find this indicator well suited to detecting the stellar activity pattern and the magnetic cycle. The analysis of the Rossiter-McLaughlin effect induced by WASP-41 b suggests that the planet could be misaligned, though an aligned orbit cannot be excluded. WASP-47 has recently been found to host two additional transiting super Earths. With such an unprecedented architecture, the WASP-47 system will be very important for understanding planetary migration.