Cool Stars 14 - Submitted Abstract # 249
This version created on 05 October 2006

Spitzer Detections of Disks around Very Low-Mass Stars in Taurus


Misato Fukagawa, Spitzer Science Center / Nagoya University
Francois Menard, Laboratoire d'Astrophysique de Grenoble
Deborah Padgett, Spitzer Science Center
Alberto Noriega-Crespo, Spitzer Science Center
Sean Carey, Spitzer Science Center
Luisa Rebull, Spitzer Science Center
Tracy Huard, Harvard-Smithsonian Center for Astrophysics
Jean-Louis Monin, Laboratoire d'Astrophysique de Grenoble
 Spitzer Taurus team

We present the Spitzer observations of very low-mass stars (VLMS) with
their masses of about 0.1 solar-mass (M5 - M6.2) in the Taurus
star-forming region.  The spectral energy distributions (SEDs) of
seven stars were measured up to 70  micron to better constrain the
outer disk structure (disk size and vertical flaring).  The SEDs and
the detection rate of about 30% at 70  micron suggest that VLMS
retaining circumstellar disks larger than 10  AU are not rare, which
implies that dynamical ejection may not be a dominant formation
mechanism of VLMS in Taurus.  The infrared SEDs show a variety of
shapes including the one with the infrared excess only at wavelengths
longer than 8 micron (a transitional disk).  The variety in one
star-forming region or compact aggregate has been known for
higher-mass T Tauri stars and even for brown dwarfs, and our results
confirmed the same nature for VLMS.  The distribution in the
color-color diagrams also did not show a significant difference from
Taurus T Tauri stars at least in our very limited sample, in which the
large scatter of the distribution may arise from the disk geometry,
small age difference (evolutionary effect), or possible multiplicity.
Our finding of one transitional disk around the VLMS suggests that the
evolutionary process such as inner disk clearing takes place in a
similar time scale to T Tauri stars.

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