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Theses

Evolution and appearance of the inner regions of circumbinary discs

Abstract : Stars are born in swirling discs of gas and dust, and roughly half of all stars exists in binary systems. The presence of a binary companion in a disc is known to open a large cavity in the inner region, however the exact nature of how this occurs is not fully known. Moreover, resolving a binary companion remains a challenging observational problem, and there exists a number of discs with observed cavities and as yet no resolved binary, leading to difficulties in inferring the presence of these companions. To investigate the cavity opening process in a circumbinary disc I perform a suite of 3D Smoothed Particle Hydrodynamics simulations using the code PHANTOM. I alter the binary orbital eccentricity, binary mass ratio, disc scale height, and the mutual inclination between the binary and the disc to understand how each of these affect the cavity over the course of 1,000 binary orbits. I find that a cavity is quickly opened on a dynamical timescale while its long-term size is set on a viscous timescale, with the final size depending on both binary and disc properties. I then compute synthetic observations using the 3D radiative transfer code MCFOST in an attempt to find observable signatures of the companion. I find that the radial motion imparted on the disc by the companion is detectable in the dynamic signatures. I also develop a metric to quantify the asymmetry in our observations and find that circumbinary discs are at least 3 times more asymmetric than single-star discs. Thus I have developed two methods to indirectly infer the presence of a binary companion in the case when it cannot be directly observed.
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https://tel.archives-ouvertes.fr/tel-03534367
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Submitted on : Wednesday, January 19, 2022 - 1:58:07 PM
Last modification on : Thursday, January 20, 2022 - 3:39:49 AM
Long-term archiving on: : Wednesday, April 20, 2022 - 6:42:09 PM

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  • HAL Id : tel-03534367, version 1

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Kieran Hirsh. Evolution and appearance of the inner regions of circumbinary discs. Astrophysics [astro-ph]. Université de Lyon, 2021. English. ⟨NNT : 2021LYSE1192⟩. ⟨tel-03534367⟩

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