Spin-orbit measurements and refined parameters for the exoplanet systems WASP-22 and WASP-26

TL;DR

This study refines the parameters of exoplanet systems WASP-22 and WASP-26 through spectroscopic and photometric observations, measuring spin-orbit angles and constraining orbital eccentricities, while also identifying a potential third body in the WASP-22 system.

Contribution

It provides new measurements of spin-orbit angles and system parameters, and identifies a possible third body in the WASP-22 system, enhancing understanding of these exoplanetary systems.

Findings

WASP-22b has a prograde orbit with a 22 +/- 16 deg spin-orbit angle.

No Rossiter-McLaughlin effect detected for WASP-26b due to low amplitude.

A third body in WASP-22 system has a minimum mass of 5.3 +/- 0.3 Mjup.

Abstract

We report on spectroscopic and photometric observations through transits of the exoplanets WASP-22b and WASP-26b, intended to determine the systems' spin-orbit angles. We combine these data with existing data to refine the system parameters. We measure a sky-projected spin-orbit angle of 22 +/- 16 deg for WASP-22b, showing the planet's orbit to be prograde and, perhaps, slightly misaligned. We do not detect the Rossiter-McLaughlin effect of WASP-26b due to its low amplitude and observation noise. We place 3-sigma upper limits on orbital eccentricity of 0.063 for WASP-22b and 0.050 for WASP-26b. After refining the drift in the systemic velocity of WASP-22 found by Maxted et al. (2010, AJ, 140, 2007) we find the third body in the system to have a minimum-mass of 5.3 +/- 0.3 Mjup (a3/5 AU)^2, where a3 is the orbital distance of the third body.