Abstract
We use high-resolution numerical simulations to study whether
gravitational instabilities within circumstellar discs can produce
astrometrically detectable motion of the central star. For discs with
masses of Mdisc= 0.1M*, which are permanently
stable against fragmentation, we find that the magnitude of the
astrometric signal depends upon the efficiency of disc cooling. Short
cooling times produce prominent filamentary spiral structures in the
disc, and lead to stellar motions that are potentially observable with
future high precision astrometric experiments. For a disc that is
marginally unstable within radii of ~10 au, we estimate astrometric
displacements of 10-102μ arcsec on decade time-scales for
a star at a distance of 100 pc. The predicted displacement is suppressed
by a factor of several in more stable discs in which the cooling time
exceeds the local dynamical time by an order of magnitude. We find that
the largest contribution comes from material in the outer regions of the
disc and hence, in the most pessimistic scenario, the stellar motions
caused by the disc could confuse astrometric searches for low-mass
planets orbiting at large radii. They are, however, unlikely to present
any complications in searches for embedded planets orbiting at small
radii, relative to the disc size, or Jupiter-mass planets or greater
orbiting at large radii.
Original language | English |
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Pages (from-to) | 227-232 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 338 |
Publication status | Published - 1 Jan 2003 |
Keywords
- accretion
- accretion discs
- astrometry
- stars: formation
- planetary systems: protoplanetary discs
- stars: pre-main-sequence