Star - Planet - Debris Disk Alignment in the HD 82943 system: Is planetary system coplanarity actually the norm?

摘要

Recent results suggest that the two planets in the HD 82943 system areinclined to the sky plane by 20 +/- 4deg. Here, we show that the debris disk inthis system is inclined by 27 +/- 4deg, thus adding strength to the derivedplanet inclinations and suggesting that the planets and debris disk areconsistent with being aligned at a level similar to the Solar System. Further,the stellar equator is inferred to be inclined by 28 +/- 4deg, suggesting thatthe entire star - planet - disk system is aligned, the first time suchalignment has been tested for radial velocity discovered planets on ~AU wideorbits. We show that the planet-disk alignment is primordial, and not theresult of planetary secular perturbations to the disk inclination. In addition,we note three other systems with planets at >10AU discovered by direct imagingthat already have good evidence of alignment, and suggest that empiricalevidence of system-wide star - planet - disk alignment is therefore emerging,with the exception of systems that host hot Jupiters. While this alignmentneeds to be tested in a larger number of systems, and is perhaps unsurprising,it is a reminder that the system should be considered as a whole whenconsidering the orientation of planetary orbits.