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

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 +/-0.20 M-Jup and eccentricity 0.29 +/- 0.02, and it orbits in 421 +/- 2 days. WASP-47 c is a planet of minimum mass 1.24 +/- 0.22 M-Jup and eccentricity 0.13+/-0.10, and it orbits in 572+/-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 similar to 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.