Volume 437, Number 2, July II 2005
|Page(s)||627 - 636|
|Section||Stellar structure and evolution|
|Published online||21 June 2005|
New insights on the AU-scale circumstellar structure of FU Orionis
Laboratoire d'Astrophysique de Grenoble, UMR CNRS/UJF 5571, BP 53, 38041 Grenoble Cedex 9, France e-mail: Fabien.Malbet@obs.ujf-grenoble.fr
2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
3 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA
4 European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching, Germany
5 Department of Astronomy, California Institute of Technology, MC 105-24, Pasadena, CA 91125
6 Center for Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139, USA
7 Michelson Science Center, California Institute of Technology, 770 S. Wilson Ave., Pasadena, CA 91125, USA
8 Observatoire de Genève, 1290 Sauverny, Switzerland
9 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
Accepted: 23 March 2005
We report new near-infrared, long-baseline interferometric observations at the AU scale of the pre-main-sequence star FU Orionis with the PTI, IOTA and VLTI interferometers. This young stellar object has been observed on 42 nights over a period of 6 years from 1998 to 2003. We have obtained 287 independent measurements of the fringe visibility with 6 different baselines ranging from 20 to 110 m in length, in the H and K bands. Our data resolves FU Ori at the AU scale, and provides new constraints at shorter baselines and shorter wavelengths. Our extensive -plane coverage, coupled with the published spectral energy distribution data, allows us to test the accretion disk scenario. We find that the most probable explanation for these observations is that FU Ori hosts an active accretion disk whose temperature law is consistent with standard models and with an accretion rate of . We are able to constrain the geometry of the disk, including an inclination of and a position angle of . In addition, a 10 percent peak-to-peak oscillation is detected in the data (at the two-sigma level) from the longest baselines, which we interpret as a possible disk hot-spot or companion. The still somewhat limited sampling and substantial measurement uncertainty prevent us from constraining the location of the spot with confidence, since many solutions yield a statistically acceptable fit. However, the oscillation in our best data set is best explained with an unresolved spot located at a projected distance of 10 ± at the 130 ± position angle and with a magnitude difference of ± 0.2 and ± 0.2 mag moving away from the center at a rate of 1.2 ± . Although this bright spot on the surface of the disk could be tracing some thermal instabilities in the disk, we propose to interpret this spot as the signature of a companion of the central FU Ori system on an extremely eccentric orbit. We speculate that the close encounter of this putative companion and the central star could be the explanation of the initial photometric rise of the luminosity of this object.
Key words: stars: pre-main-sequence / stars: individual: FU Ori / planetary systems: protoplanetary disks / infrared: stars / accretion, accretion disks / techniques: interferometric
© ESO, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.