The spin-orbit alignment of the Fomalhaut planetary system probed by optical long baseline interferometry
Abstract
Aims: We discuss the spin-orbit orientation of the Fomalhaut planetary system composed of a central A4V star, a debris disk, and a recently discovered planetary companion.
Methods: We use spectrally resolved, near-IR long baseline interferometry to obtain precise spectro-astrometric measurements across the Br-γ absorption line. The achieved astrometric accuracy of ±3 μas and the spectral resolution R=1500 from the AMBER/VLTI instrument allow us to spatially and spectrally resolve the rotating photosphere.
Results: We find a position angle {PAstar}=65° ± 3° for the stellar rotation axis, perpendicular to the literature measurement for the disk position angle ({PAdisk}=156.0 ° ± 0.3°). This is the first time such a test could be performed for a debris disk, and in a non-eclipsing system. Additionally, our measurements suggest unexpected backward-scattering properties for the circumstellar dust grains.
Conclusions: Our observations validate the standard scenario for star and planet formation in which the angular momentum of the planetary systems are expected to be colinear with the stellar spins.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 2009
- DOI:
- 10.1051/0004-6361/200911854
- arXiv:
- arXiv:0904.1688
- Bibcode:
- 2009A&A...498L..41L
- Keywords:
-
- stars: individual: Fomalhaut;
- stars: planetary systems;
- methods: observational;
- techniques: high angular resolution;
- techniques: interferometric;
- stars: rotation;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- doi:10.1051/0004-6361/200911854