Astronomy and Astrophysics – Astrophysics – Earth and Planetary Astrophysics
Scientific paper
2010-09-16
Astronomy and Astrophysics
Astrophysics
Earth and Planetary Astrophysics
18 pages, 20 figures, Accepted by MNRAS
Scientific paper
Magnetic interactions between a protostar and its accretion disc tend to induce warping in the disc and produce secular changes in the stellar spin direction, so that the spin axis may not always be perpendicular to the disc. This may help explain the recently observed spin-orbit misalignment in a number of exoplanetary systems. We study the dynamics of warped protoplanetary discs under the combined effects of magnetic warping/precession torques and internal stresses in the disc, including viscous damping of warps and propagation of bending waves. We show that when the outer disc axis is misaligned with the stellar spin axis, the disc evolves towards a warped steady-state on a timescale that depends on the disc viscosity or the bending wave propagation speed, but in all cases is much shorter than the timescale for the spin evolution (of order of a million years). Moreover, for the most likely physical parameters characterizing magnetic protostars, circumstellar discs and their interactions, the steady-state disc has a rather small warp, such that the whole disc lies approximately in a single plane determined by the outer disc boundary conditions, although more extreme parameters may give rise to larger disc warps. In agreement with our recent analysis (Lai et al. 2010) based on flat discs, we find that the back-reaction magnetic torques of the slightly warped disc on the star can either align the stellar spin axis with the disc axis or push it towards misalignment, depending on the parameters of the star-disc system. This implies that newly formed planetary systems may have a range of inclination angles between the stellar spin axis and the symmetry axis of the planetary orbits.
Foucart Francois
Lai Dong
No associations
LandOfFree
Evolution of Spin Direction of Accreting Magnetic Protostars and Spin-Orbit Misalignment in Exoplanetary Systems: II. Warped Discs does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Evolution of Spin Direction of Accreting Magnetic Protostars and Spin-Orbit Misalignment in Exoplanetary Systems: II. Warped Discs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Evolution of Spin Direction of Accreting Magnetic Protostars and Spin-Orbit Misalignment in Exoplanetary Systems: II. Warped Discs will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-28067