Hello! I am a theoretical astrophysicist interested in astrophysical fluids and how they can be modeled by numerical hydrodynamics. I particularly focus on stellar interactions, as they provide an avenue to study unsolved phenomena such as the formation of black hole binaries. I'm an active developer of the moving-mesh code MANGA and a member of the N-Body Shop collaboration.
I am currently a postdoctoral scholar at the Kavli Institute for Theoretical Physics at UC Santa Barbara. I completed my PhD in Physics in 2022 at the University of Wisconsin-Milwaukee under the advisement of Dr. Philip Chang. My thesis was titled Simulating the Common Envelope Phase Using Moving-Mesh Hydrodynamics. I graduated from Iowa State University (Go Cyclones!) in 2016 with bachelor of science degrees in Aerospace Engineering, Physics, and Mathematics.
In my free time, I enjoy playing Dungeons & Dragons and reading sci-fi/fantasy novels. I have also played the trombone for ~15 years (though I am a bit out of practice now).
Check out my Github, ORCiD, and Physics Tree pages!
Common Envelope Evolution
Common envelope evolution (CEE) is a phase in the life of a binary star system in which a giant star shares its gaseous envelope with a small companion object, such as a main sequence star or white dwarf. This process plays a role in the formation of many objects of interest to astronomers, including:
- double white dwarfs
- X-ray binaries
- binary neutron stars
- binary black holes
- progenitors of type Ia supernovae
- planetary nebulae
We carry out simulations of the common envelope phase using the moving-mesh code MANGA, with the goal of determining the efficiency with which the envelope is ejected and to find a mapping from the initial state of the binary to its final separation. The stellar evolution code MESA is used both to determine the initial structure of the giant and to provide an equation of state for the gas.
Planetary Engulfment
Similar to common envelope evolution, it is also possible for a post-main sequence star ascending the giant branch to engulf one or more of its inner planets. The planet spirals into the giant due to drag, ultimately leading to its destruction and a temporary increase in the size and luminosity of the giant. We use the adaptive mesh refinement code Athena++ to perform "wind-tunnel" simulations of the interaction between the planet and surrounding envelope.
The flow around an engulfed planet depends largely on the ability of its gravitational pull to accrete stellar material against the immense ram pressure from the oncoming fluid. In the outer envelope, gravity is strong enough to cloak the planet in a pseudo-hydrostatic halo of gas adorned by a bow shock. As it spirals in, this halo is gradually stripped off and the bow shock moves inward toward the planet surface until an abrupt transition takes place. Here a recompression shock forms behind the planet, deflecting the flow outward and creating a low-density bubble behind the planet. These two distinct morphologies are also described by different models for the drag on the planet due to both ram pressure and dynamical friction.
Bondi-Hoyle Accretion
Objects moving though a gaseous medium accrete matter from their surroundings, and knowledge of the accretion rate is important for understanding the growth and dynamics of a variety of objects. We study accretion flows using the adaptive mesh refinement code Athena++ and the moving-mesh code Arepo.
We find that for moving accretors which are small relative to their sphere of gravitational influence (e.g. black holes), the streamlines entering the accretor are essentially radial. This has the surprising consequence that the accretion rate is independent of Mach number for black holes which are moving subsonically, depending only on the gas entropy. For supersonic motion, shock waves are present which raise the entropy and thus lower the accretion rate.
Supernova Remnants (Type IIb)
When a star goes supernova, it launches a forward shock into the surrounding circumstellar medium (CSM) and sends a reverse shock backward though the ejecta. The shell of material between these shocks experiences Rayleigh-Taylor instabilities, creating turbulence which leads to synchrotron emission in the radio band. SNIIb are a subclass of supernovae which have lost most of their hydrogen envelope prior to exploding due to winds or binary interactions, and thus have a dense CSM. One such supernova is SN 1993J, which has been observed over a period of 30 years and can be compared to theoretical models to better understand the structure of the CSM and thus the mechanism of mass loss. To this end, we model SN 1993J using the 1-D hydrodynamics code RT1D, which has been calibrated to include the effects of 3-D turbulence.
Supernova Remnants (Type Ia)
Type Ia supernovae are caused by accretion onto a white dwarf from a Roche lobe-filling binary companion. This means that a large portion of the ejecta is blocked by the companion, carving out a low-density wake. We model such remnants using the expanding-grid hydrodynamics code Sprout, which allows us to follow the evolution of the remnant over several orders of magnitude in time.
We find that the forward shock is initially indented within the wake, but becomes spherical after ~1000 years. The reverse shock quickly traverses the wake and reaches the center of the remnant, leading to an asymmetrical bounce shock. This also affects the composition of the remnant by drawing material from the interstellar medium (ISM) into its center.
Magnetohydrodynamics
Magnetism is important in many areas of astrophysics, such as in the dynamics of accretion disks and the formation of jets. Often the magnetic field can be treated as "frozen into" the fluid, so that the fluid motion causes the field lines to twist and turn. The presence of the field also introduces new types of wave motion in the fluid, such as magnetosonic and Alfven waves.
Magnetism can be implemented into hydrodynamic solvers by simply adding a few terms into the governing equations. However, numerical noise can lead to the formation of magnetic monopoles, violating Gauss's law of magnetism. I work on developing techniques to combat these monopoles by either damping them or smoothing them out.
As mentioned above, magnetism is thought to play a role in common envelope evolution. Though not dynamically important over small timescales, magnetic pressure can shape the ejecta from a CE event over the course of many years. This phenomenon is thought to be responsible for the bipolar plumes of the Calabash Nebula, which are observed to be threaded by magnetic fields. Our magnetohydrodynamic solvers have shown the formation of the toroidal magnetic fields thought to drive these outflows.
Simulation Techniques
When solving the hydrodynamic equations, there are two schools of thought, each of which has inherent strengths and weaknesses. The Lagrangian interpretation models the fluid as a collection of particles, while the Eulerian interpretation divides the space into a mesh. The moving-mesh method has been developed with the goal of combining the strengths of both, using a Voronoi tessellation to draw a dynamic mesh around a set of moving particles.
I am interested in the development of moving-mesh techniques and their application to astrophysics. Despite their high computational cost, moving meshes are well-suited to a variety of problems. For example, the presence of an inner boundary condition such as a reflection or accretion boundary is desirable for a variety of studies. The use of a moving mesh allows us to construct a boundary which moves throughout the simulation domain, possibly in response to gravitational or hydrodynamic forces.
Computational Resources
The calculations described above require a large amount of computational power. To that end, I am grateful for the use of the Stampede2 and Expanse supercomputers through the NSF ACCESS program as well as the Pleiades and Electra supercomputers through the NASA Advanced Supercomputing divison. I also use the Mortimer HPC System at UWM and the Pod cluster at the California NanoSystems Institute.
Student Supervision
- Hila Glanz (Grad Student, Technion)
Co-authored a paper on Bondi-Hoyle accretion. - Joseph Farah (Grad Student, Las Cumbres Observatory)
Co-authored a paper on radio interferometry of the SN 1993J remnant. - Gabriel Kumar (Undergrad, UCSB)
Co-authoring a paper on radiation hydrodynamics of SN ejecta. - Kathlynn Simotas (Grad Student, UCSB)
Mentored a project on D6 supernovae. - Sarah Villanova-Borges (Grad Student, UWM)
Co-authored a publication on long-term evolution of CEE ejecta. - Vinaya Valsan (Grad Student, UWM)
Co-authored a publication and developed the analysis code for Vinaya's simulation output. - Sunny Wong (Grad Student, UCSB)
Collaborate on double-degenerate type Ia supernovae. - Ronan Humphrey (Grad Student, UWM)
Provide guidance on development of MANGA simulation code. - Alexandra Spaulding (Grad Student, UWM)
Provided guidance on setting up MANGA to model tidal disruption events.
Graduate Teaching Assistant (UWM)
- Phys 720: Electrodynamics I (Spring 2020)
- Phys 441: Introduction to Quantum Mechanics (Fall 2019)
- Physics Tutor (Fall 2019)
- Astron 103: Survey of Astronomy (Spring 2019)
- Phys 122: General Physics II, Non-Calculus Treatment (Fall 2017; Fall 2018)
- Phys 120: General Physics I, Non-Calculus Treatment (Spring 2018)
Undergraduate Teaching Assistant (ISU)
- Aer E 351: Astrodynamics I (Fall 2015; Spring 2016; Fall 2016)
- Aer E 192: Aerospace Seminar (Spring 2013)
Grader (ISU)
- EM 324: Mechanics of Materials (Summer 2016; Fall 2016)
- EM 274: Engineering Statics (Spring 2016)
- EM 345: Engineering Dynamics (Spring 2016)
- Aer E 310: Aerodynamics I (Fall 2015)
Other Service Work
- Postdoc Mentor for KITP Graduate Fellow, 2024
- Code of Conduct Committee, N-Body Shop Collaboration, 2023
- Progenitor Constraints via Early-time Observations of Type IIb SN 2022hnt Shock Cooling Emission
J. Farah, D. A. Howell, G. Terreran, I. Irani, J. Morag, C. Pellegrino, C. McCully, M. Newsome, E. P. Gonzalez, A. Boestrom, G. Hosseinzadeh, M. Andrews, L. Prust, D Hiramatsu
Submitted to The Astrophysical Journal - Morphology and Mach Number Dependence of Subsonic Bondi-Hoyle Accretion
Logan Prust, Hila Glanz, Lars Bildsten, Hagai Perets, Fritz Röpke
2024, The Astrophysical Journal, Volume 966, Issue 1, id.103, 11 pp. - Robust Geometric Modeling of the Supernova 1993J Ejecta at Radio Wavelengths
Joseph Farah, Giacomo Terreran, D. Andrew Howell, Michael Bietenholz, Norbert Bartel, Logan Prust, Curtis McCully, Lars Bildsten, Michael Johnson
In preparation - Flow Morphology of a Supersonic Gravitating Sphere
Logan Prust & Lars Bildsten
2024, Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 2, pp.2869-2886 - Envelope Ejection and the Transition to Homologous Expansion in Common-Envelope Events
Vinaya Valsan, Sarah Villanova-Borges, Logan Prust, Philip Chang
2023, Monthly Notices of the Royal Astronomical Society, Volume 526, Issue 4, pp.5365-5373 - The Effect of Hydrodynamic Forces on Common Envelope Evolution
Logan Prust
Submitted to Monthly Notices of the Royal Astronomical Society - The Role of Radiation in Common Envelope Evolution
Logan Prust
2022, Proceedings of the Wisconsin Space Conference, doi: 10.17307/wsc.v1i1.346 - Moving Boundary Conditions in Common Envelope Evolution
Logan Prust
2022, Proceedings of the Wisconsin Space Conference, doi: 10.17307/wsc.v1i1.327 - Moving and Reactive Boundary Conditions in Moving-Mesh Hydrodynamics
Logan Prust
2020, Monthly Notices of the Royal Astronomical Society, Volume 494, Issue 4, pp.4616-4626 - Common Envelope Evolution on a Moving Mesh
Logan Prust
2020, Proceedings of the Wisconsin Space Conference, doi: 10.17307/wsc.v1i1.306 - Common Envelope Evolution on a Moving Mesh
Logan Prust & Philip Chang
2019, Monthly Notices of the Royal Astronomical Society, Volume 486, Issue 4, p.5809-5818
Conference and Seminar Talks
- TBA
TBA, AAS Winter Meeting
Oxon Hill, MD, USA, Jan 2025
- A Birdwatcher's Guide to D6 Supernova Remnants
Invited talk, ZTF Theory Network Meeting
Santa Margarita, CA, USA, Sept 2024
- Evolution of Ejecta Wakes in Supernova Remnants
Poster, Rise_Time 2024: Explosive Astrophysics in the Era of High-Cadence Astronomy
West Lafayette, IN, USA, Aug 2024
[Download ePoster] - Shock Waves in Asymmetrical Supernova Remnants
Seminar talk, Graduate Simulation Seminar Series (GS3)
Santa Barbara, CA, USA, July 2024
- Reverse Shocks in D6 Supernovae
Invited talk, ZTF Theory Network Meeting: WD Detonations
Cambria, CA, USA, June 2024
- Shock Trajectories in Asymmetrical Supernova Remnants
Blackboard talk, KITP Locals Lunch
Santa Barbara, CA, USA, May 2024
- Morphology and Entropy Dependence of Subsonic Bondi-Hoyle Accretion
Seminar talk, UCSB Astrophysics Theory Seminar
Santa Barbara, CA, USA, Oct 2023
- Black Hole Accretion as a Nozzle Flow
Blackboard talk, KITP Locals Lunch
Santa Barbara, CA, USA, Oct 2023
- Flow Morphology in Planetary Engulfment Events
Invited talk, ZTF Theory Network Meeting
Santa Margarita, CA, USA, Sept 2023
- Hydrodynamical Simulation Techniques in Astrophysics
Seminar talk, Graduate Simulation Seminar Series (GS3)
Santa Barbara, CA, USA, Aug 2023
- Flow Morphology in Planetary Engulfment Events
ePoster, EAS Annual Meeting
Krakow, Poland, July 2023
[Download ePoster] - Managing Friction in Planet-Star Relationships
Seminar talk, UCSB Astrophysics Theory Seminar
Santa Barbara, CA, USA, May 2023 - Planetary Engulfment in Athena++
Session talk, Flatiron Athena++ Workshop
New York, NY, USA, May 2023 - Flow Morphology of a Supersonic Gravitating Sphere
Blackboard talk, KITP Locals Lunch
Santa Barbara, CA, USA, Apr 2023 - Flow Morphology in Post-Main Sequence Planetary Engulfment
Seminar talk, UCSB Astro Lunch
Santa Barbara, CA, USA, Apr 2023 - Long-Term Evolution in Simulations of the Common Envelope Phase
Invited talk, ZTF Theory Network Meeting
Santa Margarita, CA, USA, Sept 2022 - Modeling Common Envelopes on a Moving Mesh
Blackboard talk, KITP Locals Lunch
Santa Barbara, CA, USA, Sept 2022 - Simulating the Common Envelope Phase on a Moving Mesh
Session talk, Flatiron N-Body Workshop
New York, NY, USA, June 2022 - New Physics in Simulations of the Common Envelope Phase
Session talk, Midwest Relativity Meeting
Champaign, IL, USA, Nov 2021 - Moving Boundary Conditions in Common Envelope Evolution
Contributed talk, Common Envelope Physics and Outcomes
Virtual, Aug 2021 - Simulating Common Envelope Evolution on a Moving Mesh
Invited talk, Wisconsin Space Conference
Milwaukee, WI, USA, Aug 2021 - Moving and Reactive Boundary Conditions on a Moving Mesh
Contributed talk, N-Body Shop Excellence Conference
Virtual, Jan 2021 - Moving Boundary Conditions in Common Envelope Evolution
Session talk, Midwest Relativity Meeting
Notre Dame, IN, USA, Oct 2020 - Simulating the CE Phase Using Moving-Mesh Hydrodynamics
Contributed talk, EAS Annual Meeting
Leiden, Netherlands, July 2020 - Moving-Mesh Hydrodynamics Using MANGA
Seminar talk, CGCA Seminar Series
Milwaukee, WI, USA, Dec 2019 - Simulating the Common Envelope Phase in Binary Stars
Invited talk, Wisconsin Space Conference
Platteville, WI, USA, Aug 2019 - CEE on a Moving Mesh with MANGA
Invited talk, Flatiron CEE Workshop
New York, NY, USA, May 2019 - Common Envelope Evolution on a Moving Mesh
Session talk, Midwest Relativity Meeting
Milwaukee, WI, USA, Oct 2018
Other Workshops Attended
- Stellar Interactions and the Transients They Cause
Aspen Center for Physics
Aspen, CO, July 2023 - Physics and Astrophysics of Common Envelopes (PACE)
Los Alamos National Laboratory
Los Alamos, NM, May 2022 - MESA Summer School
UC Santa Barbara
Santa Barbara, CA, Aug 2019 - Various KITP Programs:
- White Dwarfs from Physics to Astrophysics
- Multiphase Flows in Geophysics and the Environment
- Turbulence in Astrophysical Environments
- Towards a Physical Understanding of Tidal Disruption Events
- Dark Matter Theory, Simulation, and Analysis in the Era of Large Surveys
- Interconnections between the Physics of Plasmas and Self-gravitating Systems
Download my CV here.
Office: Kohn Hall, Room 2411, UCSB
Email: ljprust (at) kitp (dot) ucsb (dot) edu
Top photo credit: Jeff Liang, UCSB
