Issue |
A&A
Volume 498, Number 3, May II 2009
|
|
---|---|---|
Page(s) | L41 - L44 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361/200911854 | |
Published online | 29 April 2009 |
Letter to the Editor
The spin-orbit alignment of the Fomalhaut planetary system probed by optical long baseline interferometry*
1
European Southern Observatory, Casilla 19001, Santiago 19, Chile e-mail: jlebouqu@eso.org
2
Institut d'Astrophysique et de Géophysique, Université de Liège, 17 allée du Six Août, 4000 Sart Tilman, Belgium
3
INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
Received:
16
February
2009
Accepted:
9
April
2009
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- absorption line. The achieved astrometric accuracy of
as and the spectral resolution
from the AMBER/VLTI
instrument allow us to spatially and spectrally resolve the rotating photosphere.
Results. We find a position angle ±
for the stellar rotation axis, perpendicular to the literature measurement
for the disk position angle (
±
). 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.
Key words: stars: individual: Fomalhaut / stars: planetary systems / methods: observational / techniques: high angular resolution / techniques: interferometric / stars: rotation
© ESO, 2009
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