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

Figure 6.5: Observation and model of the spiral structure in the disk of HD 141569. Left Panel: HST/ACS
optical observations. The image is de-projected to provide a pole-on view of the disk.Middle Panel: Synthetic
image of disk showing the spiral structure caused by the remote companions. Right Panel: Geometry of the
multiple system.
N. Grosso who participates actively in all programmes, together with T.Montmerle (Astromol). Other members
of FOST are actively involved in XEST (Bouvier, Dougados, Ménard, Monin, and PhD student Guieu). The
surveys we participate in are:
• The Chandra Orion Ultradeep Project (COUP) COUP is a nearly continuous observation of the Orion
nebula cluster over about 13. days that took place in Jan. 2003. It yielded an exceptionally deep total onsource
exposure time of about 10 days. A total 13 papers, with 8 co-signed by N.Grosso and T.Montmerle
(ASTROMOL), were published in the October 2005 COUP special issue of The Astrophysical Journal
Supplement.
• The X-ray Emission Survey of the Taurus Molecular Cloud (XEST) This X-ray survey of the Taurus
Molecular Cloud with XMM-Newton was proposed by Manuel Güdel (Paul-Scherrer Institut, Zürich). It
is closely linked to the Taurus optical survey carried by our group at CFHT, and with a Spitzer survey
(PI is D.Padgett, Caltech) of the same zone. Data is currently being analysed for all three surveys.
• The Deep Rho Oph XMM-Newton Observation (DROXO) The dense core F of the ρ Ophiuchi dark cloud
was first studied in X-Rays by H.Ozawa (postdoc from April 2002 to March 2004) with an exposure of
33 ks with XMM-Newton. Ozawa et al. (2005) detected 87 X-ray sources, of whom 25 are new X-ray
sources. DROXO, proposed by Salvatore Sciortino (Palermo observatory), is a ten day long XMM-Newton
observation of roughly the same area to study spectral and variability properties of young stellars objects.
Observations have been performed on March 2005.
Spitzer Legacy surveys: Cores-to-Disks (C2D)
Our team is involved in the Spitzer c2d Legacy program designed to study the evolution of circumstellar matter
’From Molecular Cores to Planet-Forming Disks”. This program utilizes in particular the improved sensitivity
of the Spitzer InfraRed Spectrograph (IRS5, 5-35 micron) to study ices towards low-mass embedded protostars
(Boogert et al., 2004) and toward extincted background stars. The Spitzer/c2d spectra toward a variety of
solar-type PMS stars also greatly expand the study of infrared emission features in solar-mass stars, which
previously were restricted primarily to ground-based studies in the 10 micron window. A large fraction of the
silicates features are weak and flat, consistent with micron-sized grains indicating fast grain growth. In addition,
approximately half of the T Tauri star spectra show crystalline silicate features near 28 and 33microns indicating
significant processing when compared to interstellar grains (Kessler-Silacci, Augereau et al., submitted).
Furthermore, PAH emission is observed towards at least 5 T Tauri stars out of 33, with 11 tentative detections
still to be confirmed, resulting in a lower limit of 15% detection of PAH in T Tauri stars (Geers, Augereau et al.,
in prep). Although PAH features are widely observed, in particular in circumstellar disks around Herbig stars,
there was no consensus before these results on the presence of PAHs in protoplanetary disks around T Tauri
stars and whether or not they were receiving sufficient stellar radiation to produce observable signatures.
89