Paper: astro-ph/0509362
Date: Tue, 13 Sep 2005 20:33:26 GMT (123kb)

Title: Disc orientations in pre-main-sequence multiple systems. A study in
southern star formation regions

Authors: Jean-Louis Monin, Francois Menard and Nicolas Peretto

Comments: 13 pages, 11 figures, accepted in Astronomy and Astrophysics.
accepted in Astronomy and Astrophysics (A&A)
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Classical T Tauri stars are encircled by accretion discs most of the time
unresolved by conventional imaging observation. However, numerical simulations
show that unresolved aperture linear polarimetry can be used to extract
information about the geometry of the immediate circumstellar medium that
scatter the starlight. Monin, Menard & Duchene (1998) previously suggested that
polarimetry can be used to trace the relative orientation of discs in young
binary systems in order to shed light on the stellar and planet formation
process. In this paper, we report on new VLT/FORS1 optical linear polarisation
measurements of 23 southern binaries spanning a range of separation from 0.8''
to 10''. In each field, the polarisation of the central binary is extracted, as
well as the polarisation of nearby stars in order to estimate the local
interstellar polarisation. We find that, in general, the linear polarisation
vectors of individual components in binary systems tend to be parallel to each
other. The amplitude of their polarisations are also correlated. These findings
are in agreement with our previous work and extend the trend to smaller
separations. They are also similar to other studies, e.g., Donar et al. 1999;
Jensen et al. 2000, 2004; Wolf et al. 2001. However, we also find a few systems
showing large differences in polarisation level, possibly indicating different
inclinations to the line-of-sight for their discs.

\\ ( http://arXiv.org/abs/astro-ph/0509362 , 123kb)