Peculiar architectures for the WASP-53 and WASP-81 planet-hosting systems

TL;DR

This paper reports the discovery of two new transiting hot Jupiters in systems also hosting massive brown dwarf companions, providing insights into their formation and orbital dynamics through radial velocity and astrometric observations.

Contribution

It presents the detection and characterization of two planetary systems with hot Jupiters and massive brown dwarfs, and discusses their formation scenarios and orbital alignments.

Findings

Detection of two transiting hot Jupiters in WASP-53 and WASP-81 systems.

Identification of massive brown dwarf companions with eccentric orbits.

Alignment of WASP-53b with the stellar spin axis.

Abstract

We report the detection of two new systems containing transiting planets. Both were identified by WASP as worthy transiting planet candidates. Radial-velocity observations quickly verified that the photometric signals were indeed produced by two transiting hot Jupiters. Our observations also show the presence of additional Doppler signals. In addition to short-period hot Jupiters, we find that the WASP-53 and WASP-81 systems also host brown dwarfs, on fairly eccentric orbits with semi-major axes of a few astronomical units. WASP-53c is over 16 $M_{\rm Jup} \sin i_{\rm c}$ and WASP-81c is 57 $M_{\rm Jup} \sin i_{\rm c}$. The presence of these tight, massive companions restricts theories of how the inner planets were assembled. We propose two alternative interpretations: a formation of the hot Jupiters within the snow line, or the late dynamical arrival of the brown dwarfs after disc-dispersal. We also attempted to measure the Rossiter--McLaughlin effect for both hot Jupiters. In the case of WASP-81b we fail to detect a signal. For WASP-53b we find that the planet is aligned with respect to the stellar spin axis. In addition we explore the prospect of transit timing variations, and of using Gaia's astrometry to measure the true masses of both brown dwarfs and also their relative inclination with respect to the inner transiting hot Jupiters.