Untitled - Laboratoire d'Astrophysique de l'Observatoire de Grenoble

393254 (5MJup at 55 AU) & AB Pic (13-14 MJup at 250AU)). These results were obtained with the
NACO/VLT Adaptive optics instrument, built in part at LAOG. (Chauvin et al. 2004, 2005a, 2005b.)
• Dynamical masses: First astrometric mass determination for a planet, around Gliese 876b: 1.89±0.34MJup
(Benedict et al. 2002). Similarly, astrometric meaurements of stellar masses in binary systems. Accuracies
on the mass of a few percents are reached on nearby L dwarf 2MASSW J0746425+2000321 (Bouy et al.
2004) and ∼ 10% for young stars V773 Tau, DF Tau, and TWA 5 (Duchêne et al. 2003).
• The Universality of the “present day” Mass Function observed down to at least 30 Mjup (the
sensitivity limit of the surveys carried) in several young open clusters (e.g., Moraux, Bouvier, & Clarke
2005). Improvements, i.e., completeness down to a few MJup, is expected soon after the commissioning
of WIRCAM/CFHT, built partly at LAOG.
• The very inner structure of young B star MWC 297 revealed by NIR interferometry. For the first
time, the respective contributions from the disk and the wind are separated spatially & spectrally within
the inner 1AU of the central source. These results were obtained with the interferometric near-infrared
three- telescope recombiner AMBER/VLT, built in part at LAOG. (Malbet et al. 2005).
The highlights listed above will also be found in the executive summary of the present document. It is
significant that three of these four highlights from FOST were obtained with technology “made in LAOG”
and also obtained by young members of FOST. This is a direct consequence of the good adequation (the term
synergy being probably more appropriate) between the science goals of FOST and the activities of the technical
group. However, FOST being a large group, it is difficult, and ultimately unfair to many of its members, to
limit the number of highlights to a short handful for a period of 4 years. Below are listed a few other interesting
results.
• Discovery of Earth-mass planets around Mu Arae (14 Earth masses, Santos et al. (2004)) and around
the M dwarf Gliese 581 (17 Earth masses, Bonfils et al. (2005), in press).
• Spatially resolved emission from Nanograins and PAH’s in disks of intermediate mass stars evidenced
by mid-IR spectroscopy and direct imaging. (Augereau et al. 2005, in prep.; Ménard, Pinte, &
Duchêne, in collaboration with CEA/Saclay). The continuum thermal infrared imaging of T Tauri
disks, seen in scattered light up to 12µm in this case, revealing the first clear observational signs of vertical
dust settling. (McCabe et al. 2003).
• Monitoring of X-ray variations in V1647 Ori (McNeil’s nebula) to study the star-disk interaction
zone during an enhanced accretion phase: evidence for a powerful accretion shock on the photosphere of
a low-mass star. (Grosso et al. (2005)).
• The non-steady state of the accretion and ejection processes revealed at all timescales covered
by our monitoring campaigns (from a few minutes to years). See Dougados et al. (2005) for a review.
• Survey for Binaries in embedded protostars to identify the initial conditions for star formation /
early stellar evolution immediately after fragmentation of the molecular core. (Duchêne et al. 2004).
• Dynamical models of the circumbinary ring aroung GG Tau to explain the puzzling sharp outer edge.
(Beust & Dutrey (2005a,b)), and of the very young debris disks HD 141569 to search for traces of planets
(Augereau & Papaloizou (2004)).
• Discovery of several new brown dwarfs in the Taurus cloud, helping to show that the number
fraction of brown dwarfs in this low density star forming region is consistent with the ones in denser
regions like Orion.(Guieu et al., 2006, A&A 446, 485).
6.3 Selected Topics in Star Formation and Early Stellar Evolution
Accretion disks are key ingredients in the cocktail of events that lead from the collapse of a molecular cloud to
the formation of a solar-like star. They are the entities by which the infalling material transits on its way to
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