Issue |
A&A
Volume 455, Number 2, August IV 2006
|
|
---|---|---|
Page(s) | 509 - 519 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20064907 | |
Published online | 04 August 2006 |
Dust distributions in debris disks: effects of gravity, radiation pressure and collisions
1
Astrophysikalisches Institute, Friedrich-Schiller-Universität Jena, Schillergäßchen 2–3, 07745 Jena, Germany e-mail: krivov@astro.uni-jena.de
2
LASP, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303, USA
Received:
24
January
2006
Accepted:
22
March
2006
We model a typical debris disk, treated as an idealized ensemble of dust particles, exposed to
stellar gravity and direct radiation pressure and experiencing fragmenting collisions.
Applying the kinetic method of statistical physics, written in orbital elements, we
calculate size and spatial distibutions expected in a steady-state disk, investigate timescales
needed to reach the steady state, and calculate mass loss rates.
Particular numerical examples are given for the debris disk around Vega.
The disk should comprise a population of larger grains in bound orbits and a population
of smaller particles in hyperbolic orbits. The cross section area is dominated
by the smallest grains that still can stay in bound orbits, for Vega about
10 in radius.
The size distribution is wavy, implying secondary peaks in the size
distribution at larger sizes.
The radial profile of the pole-on surface density or the optical depth in the
steady-state disk
has a power-law index between about -1 and -2.
It cannot be much steeper even if dust production is confined to a narrow
planetesimal belt, because collisional grinding produces smaller and smaller
grains, and radiation pressure pumps up their orbital eccentricities and spreads
them outward, which flattens the radial profile.
The timescales to reach a steady state depend on grain sizes and distance from
the star.
For Vega, they are about 1 Myr for grains up to some hundred
at 100 AU.
The total mass of the Vega disk needed to produce the observed amount of micron and
submillimeter-sized dust does not exceed several earth masses for an upper size limit
of parent bodies of about 1 km.
The collisional depletion of the disk occurs on Gyr timescales.
Key words: planetary systems: formation / circumstellar matter / meteors, meteoroids / celestial mechanics / stars: individual: Vega
© ESO, 2006
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