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Disk, Tidal Disruption and R Scultoris Project Updates
Discs From Tidally Disrupted Companions:
Animation:
Tidal Disruption Simulations:
Goals →
1.) Investigate Bonnor-Ebert Sphere stability in a hot wind-tunnel
2.) Will a disk form from the cold tidally disrupted material?
3.) What is the fraction of material that forms a disk?
Just to mention: I wrote my own RK4 code in python that can modify the AGB profiles from MESA. Iterates over point mass, alpha, and central density, and integrates the pressure.
Animation:
R sculptoris:
I am working with Zhuo to simulate the system R Sculptoris, This will be similar to the L2 Puppis Paper where we attempt to predict the binary parameters and generate synthetic images with RADMC-3D. As of now Zhuohas prepaired a module to run and I am sorting out how the refinement should work.
Animation:
Accretion Disk Update
I have been working on simulating an accretion disk embedded in the center of an AGB star. Previous simulations have utilized a sink particle that relieved thermal energy and led to very high accretion rates. Our sink particle is set to “NOACCRETION ”.
The box size is 10e11 cm
Accretion disk has Radius of 2*10e10 cm and Height of 5*10e9 cm
Animations of the density (Top Down):
and Temperature (Side):
My first attempt to look at the accretion rate was to define a momentum flux with:
p = rho*v
dQ = p dot dA
Summing dQ over a surface yields the flow rate through that surface, I did this with spheres. The next animation shows the accretion rate in solar masses per year (y-axis) through spheres of different radii (x-axis) over time <note: positive value correspond to outward flow>:
For a general sense of the direction of flow this animation shows red as outward flow and blue as inward:
To represent accretion clearly Luke and Eric suggested calculating the total mass as a function of time. (it is much better)
The total mass inside a sphere of radius 0.4e10 cm:
Mass inside shells of constant thickness (0.05e10cm) and different outer radii:
Mass inside cylinder of disk height and radius 0.75e10 cm:
Mass inside hollow cylinder of disk height, constant thickness (0.125e10cm) and different radii:
Constucting an accretion disk around an RG and AGB star
For my masters level thesis, I plan complete and analyze MHD simulations of an accretion disk around the center of a RG and AGB star to investigate the stability and magnetic field generation . This is in an attempt to computationally verify the suggestion that High Field Magnetic White Dwarfs are the result of a Common Envelope, Nordhaus et al. 2011:
Link:https://arxiv.org/abs/1010.1529
To do this I have looked to Ohlmann’s thesis and previous blog posts made by Luke:
1.) Run The Mesa Stellar Evolution to Generate density, pressure, and temperature profiles at different points in time.
2.) The idea in Nordhaus et al. 2011 is that magnetic field is built up by the engulfment and the accretion of a companion. This is most likely when the radius is at a maximum, So I identified these maximum. (Radius (log[R/Rsun]) vs Time (years) for a 2 solar mass star)
3.) Modify those profiles with the modified-lane-emdan equations in accordance with Ohlmanns thesis (Link:https://archiv.ub.uni-heidelberg.de/volltextserver/21513/1/thesis-sohlmann.pdf) (Lukes Code)
Link:http://www.pas.rochester.edu/~lchamandy/Presentations/profile_blog1.pdf
4.) Set the central mass by hand such that the mass contained within the smoothing radius is the same as before modification. Place onto grid with at least 10 cells across smoothing radius
5.) If the central density is stable then I can move on to adding an accretion disk to the central region of the simulation.
Disk parameters: R ~ 10e10 cm
H ~ 10e9 cm M ~10 Jupiter Masses
