Dusty clumps in circumbinary discs.
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Date
2019
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Abstract
Protoplanetary discs are structures formed by gas and dust that form during the first stages
of the stellar evolution. Protoplanetary discs also are the birthplace of planets, moons,
and asteroids like the ones we observe in our Solar System. However, protoplanetary disc
structure varies amongst different systems. A good understanding of disc evolution and
dynamics is required for a comprehensive view of planet formation. Recent observations
have revealed that protoplanetary discs often exhibit cavities and azimuthal asymmetries
such as dust traps and clumps. The presence of a stellar binary system in the inner disc
regions has been proposed to explain the formation of these structures. In that case,
the protoplanetary disc should be reclassified as circumbinary. Here, I study the dust
and gas dynamics in circumbinary discs around eccentric and inclined binaries. This is
done through two-fluid simulations of circumbinary discs, considering different values of
the binary eccentricity and inclination. The simulations are made using phantom; a
three-dimensional smoothed particle hydrodynamics code. I find that two kinds of dust
structures can form in the disc: a single horseshoe-shaped clump, on top of a similar
gaseous over-density; or numerous clumps, distributed along the inner disc rim. The latter
features form through the complex interplay between the dust particles and the gaseous
spirals caused by the binary. All these clumps survive between one and several tens
of orbital periods at the feature location. I show that their evolution strongly depends
on the gas–dust coupling and the binary parameters. Interestingly, these asymmetric
features could in principle be used to infer or constrain the orbital parameters of a stellar
companion — potentially unseen — inside the inner disc cavity. Finally, I apply these
findings to the disc around AB Aurigae. The dusty clumps observed in this work suggest
that circumbinary discs are promising places to form planetesimals and even planets,
contrary to what was previously thought due to high relative velocity among solids.
Description
Tesis (Master in Astrophysics)--Pontificia Universidad Católica de Chile, 2019