Tidal Disruption Events

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Thin Tilted Accretion Disks

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Optical Tweezer Arrays

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Cosmic Ray Detecting CubeSat

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Extreme Redshift Galaxies

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Atomic Physics in Kilonovae Ejecta

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What is a Tidal Disruption Event?

When a star passes too close to a supermassive black hole (BH), the BH’s tidal forces pull the star apart into a stream of debris in a so-called tidal disruption event (TDE). Some of the stellar debris is gravitationally bound to the BH and accretes at rates far above the Eddington limit, resulting in a bright flare and the formation of a “debris disk” on a timescale of weeks to months. Although TDEs are relatively rare, with a rate of one per 1,000 to 10,000 years per galaxy, they have a broad astrophysical implications.

  1. Only ~30% of galaxies host active galactic nuclei (AGN). TDEs provide a rare glimpse of the central BHs of the quiescent majority of galaxies, allowing astronomers to better understand the fueling modes for supermassive BHs and their growth mechanisms and evolution.
  2. TDEs also offer a clean laboratory for studying accretion physics because the accretion rate is set by only a handful of orbital and stellar structure parameters. The accretion rate sweeps through multiple accretion regimes, from super- to sub-Eddington, on relatively short timescales.
  3. The properties of TDE flares depend on the properties of the disrupted star. Therefore, TDEs probe the stellar populations and kinematics of the galactic centers where the majority of events are produced.

Energy Dissipation in TDEs

Working with Prof. Sasha Tchekhovskoy, Prof. Eric Coughlin, and Prof. Nicholas Stone, I use the smooth particle hydrodynamics (SPH) code PHANTOM and the general relativistic hydrodynamics (GRHD) code H-AMR, developed by Matthew Liska, to simulate deeply-penetrating tidal disruption events and the resulting debris disks. In my first published work, I analyze these simulations to understand the physical processes that drive the circularization of the stellar debris. I find that circularization of the most bound debris is dominated by periodic self-intersections caused by general relativistic precession and that circularization at later times is dominated by hydrodynamic instabilities at the debris-disk interface.

from Andalman+2022

Current and Future Work

I am currently working on new TDE simulations which incorporate magnetic fields to investigate the role of the magnetorotational instability (MRI) in driving circularization. These simulations will also test the fossil disk hypothesis, which states that TDEs pick up the requisite magnetic flux to power a jet from a pre-existing accretion disk. The new simulations will cover longer timescales than previous simulations, allowing me to probe the physics of the debris disk near the time of peak fallback. I am also working on applying analytical models to my simulation data to understand how information about the debris disk geometry and viewing angle is encoded in TDE spectra.


  • Andalman, Z. L.; Liska, M. T. P.; Tchekhovskoy, A.; Coughlin, E. R.; Stone, N. Tidal Disruption Discs Formed and Fed by Stream-stream and Stream-disc Interactions in Global GRHD Simulations, 2022, Monthly Notices of the Royal Astronomical Society, Volume 510, Issue 2, pp. 1627-1648, arXiv:2008.04922