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Talks and posters

UKEXOM 2021


Sahl Rowther -- Giant Planets Can Suppress Gravitational Instabilities In Protoplanetary Discs

The work covered in this talk is described in Rowther et al. 2020.


Thu 22 Apr 2021, 16:00

KITP Online Conference: White Dwarfs from Physics to Astrophysics


Christopher Manser -- Gaseous planetary discs around white dwarfs

Mon 29 Mar 2021, 10:30

Five Years After HL Tau


Sahl Rowther -- Are Gravitationally Unstable Protoplanetary Discs Rare?

The work covered in this talk is described in Rowther et al. 2020.


Rebecca Nealon -- Spirals, Shadows and Precession in HD 100453 Part 2

Part 1 can be viewed here.

Dimitri Veras - Constraining Planet Formation Around 6-8 Solar Mass Stars

The work covered in this talk is described in Veras et al. 2020.


Mon 07 Dec 2020, 00:00

Exoplanet Demographics


Christopher Manser -- Doppler Imaging of a Second Planetary Debris Disc Around a White Dwarf

Talk begins at 4:16:02.


Dimitri Veras -- Full-lifetime Simulations of Planetary Systems

Talk begins at 2:00:00.

Catriona McDonald -- Triaxial Asteroids as Reservoirs for Planetary Debris around White Dwarfs

Here, we present an analytical framework incorporating tidal, self-gravitational and internal strength forces to triaxial ellipsoids approaching a white dwarf on extremely eccentric (e ~ 1) orbits. Such extreme orbits could be produced by dynamic interactions with planets in the white dwarf system. The subsequent disruption of the asteroids is split into three distinct regimes: tidal fragmentation, sublimation, and direct impact. This framework is extended to cover a simplified Main Belt analogue of 100 planetesimals with an observational size distribution and randomly chosen shape model and material, for a range of white dwarf temperatures. We find that using a spherical shape model consistently underestimates where sublimation occurs and overestimates fragmentation distance. The small spatial scales of white dwarf planetary systems can cause these discrepancies to have a large effect on predicted debris distributions. Our results allow us to place constraints on the expected planetary debris from asteroids at different white dwarf cooling ages and motivates future studies to include more accurate shape models

Thu 12 Nov 2020, 00:00

Exoplanets III

Sahl Rowther -- Hiding Signatures of Gravitational Instability in Protoplanetary Discs

We carry out three-dimensional smoothed particle hydrodynamics simulations to show that a migrating giant planet strongly suppresses the spiral structure in self-gravitating disks. We present mock Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations that show that in the absence of a planet, spiral arms due to gravitational instability are easily observed. Whereas in the presence of a giant planet, the spiral structures are suppressed by the migrating planet resulting in a largely axisymmetric disk with a ring and gap structure. Our modeling of the gas kinematics shows that the planet's presence could be inferred, for example, using optically thin 13C16O. Our results show that it is not necessary to limit the gas mass of disks by assuming high dust-to-gas mass ratios in order to explain a lack of spiral features that would otherwise be expected in high-mass disks.

Mon 27 Jul 2020, 00:00