MAGNETIC ORIGINS OF THE STELLAR MASS-OBLIQUITY CORRELATION IN PLANETARY SYSTEMS

• Published in: The Astrophysical journal 2015-10, Vol.811 (2), p.82
• Main Authors: Spalding, Christopher, Batygin, Konstantin
• Format: Article
• Language: English
• Subjects: ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DIPOLES; EXCITATION; MAGNETIC FIELDS; MAGNETIC STARS; MASS; ORBITS; PLANETS; planets and satellites: formation; protoplanetary disks; PROTOPLANETS; SATELLITES; T TAURI STARS
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.1088/0004-637X/811/2/82

ABSTRACT Detailed observational characterization of transiting exoplanet systems has revealed that the spin-axes of massive ( ) stars often exhibit substantial misalignments with respect to the orbits of the planets they host. Conversely, lower-mass stars tend to only have limited obliquities. A similar trend has recently emerged within the observational data set of young stars' magnetic field strengths: massive T-Tauri stars tend to have dipole fields that are ∼10 times weaker than their less-massive counterparts. Here we show that the associated dependence of magnetic star-disk torques upon stellar mass naturally explains the observed spin-orbit misalignment trend, provided that misalignments are obtained within the disk-hosting phase. Magnetic torques act to realign the stellar spin-axes of lower-mass stars with the disk plane on a timescale significantly shorter than the typical disk lifetime, whereas the same effect operates on a much longer timescale for massive stars. Cumulatively, our results point to a primordial excitation of extrasolar spin-orbit misalignment, signalling consistency with disk-driven migration as the dominant transport mechanism for short-period planets. Furthermore, we predict that spin-orbit misalignments in systems where close-in planets show signatures of dynamical, post-nebular emplacement will not follow the observed correlation with stellar mass.