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Relativisitc Physics Seminar
Relativisitc Physics Seminar
Accretion-induced collapse of white dwarfs: gravitational waves, magnetized jets and newborn magnetars
Accretion-induced collapse of white dwarfs: gravitational waves, magnetized jets and newborn magnetars
Organizers
Speaker
Luis Felipe Longo Micchi
Time
Thursday, October 22, 2026 2:30 PM - 3:30 PM
Venue
A3-2-301
Online
Zoom 928 682 9093
(BIMSA)
Abstract
A white dwarf that accretes mass towards the Chandrasekhar limit can collapse instead of exploding. Electron capture in its core removes the pressure support, and the star collapses into a neutron star. Such accretion-induced collapse (AIC) is a multimessenger source of gravitational waves, neutrinos, and electromagnetic transients. It has been proposed as the engine behind long gamma-ray bursts with kilonova counterparts, such as GRB 211211A and GRB 230307A. These events are hard to reconcile with compact-binary mergers, whose remnant disks are drained within $\lesssim 1$ s.
In this talk, I present general-relativistic simulations that follow AIC from collapse to the formation of the remnant. First, 3D GR hydrodynamics simulations with neutrino transport show that rotation raises the gravitational-wave signal by one to two orders of magnitude. The signal peaks near $1$ kHz and would be detectable out to $\sim 10$ Mpc by Cosmic Explorer. Second, 2D GR neutrino-MHD simulations with initial fields of $10^{9}$–$10^{12}$ G produce magnetically driven jets. Their spin-down times are tens of seconds, of the same order as $T_{90}$, and they eject up to $0.13,\Msun$ of material with $Y_e \leq 0.25$. The resulting kilonova light curves agree with the observed ones. Finally, I discuss the newborn proto-magnetar: a rigidly rotating core with $B_\mathrm{tor} \sim 10^{14}$ G, in which winding erases the memory of the initial toroidal field. Once the magnetic energy reaches $\sim 10%$ of the kinetic energy, the remnant flares, and the flare energy goes into the kinetic energy of the ejecta. I close with the open questions on the boundary between collapse and thermonuclear explosion, and on 3D magnetized models.
In this talk, I present general-relativistic simulations that follow AIC from collapse to the formation of the remnant. First, 3D GR hydrodynamics simulations with neutrino transport show that rotation raises the gravitational-wave signal by one to two orders of magnitude. The signal peaks near $1$ kHz and would be detectable out to $\sim 10$ Mpc by Cosmic Explorer. Second, 2D GR neutrino-MHD simulations with initial fields of $10^{9}$–$10^{12}$ G produce magnetically driven jets. Their spin-down times are tens of seconds, of the same order as $T_{90}$, and they eject up to $0.13,\Msun$ of material with $Y_e \leq 0.25$. The resulting kilonova light curves agree with the observed ones. Finally, I discuss the newborn proto-magnetar: a rigidly rotating core with $B_\mathrm{tor} \sim 10^{14}$ G, in which winding erases the memory of the initial toroidal field. Once the magnetic energy reaches $\sim 10%$ of the kinetic energy, the remnant flares, and the flare energy goes into the kinetic energy of the ejecta. I close with the open questions on the boundary between collapse and thermonuclear explosion, and on 3D magnetized models.
Speaker Intro
Luis Felipe Longo Micchi focuses on computational astrophysics in order to study multiple events of astrophysical interest. He graduated from the Federal University of Rio de Janeiro and then earned a Master of Science in the Brazilian Center of Physical Research on the topic of Perturbation Theory of Kerr Black holes. During his PhD at the Federal University of ABC, he researched modified boundary conditions on the Teukolsky equation in collaboration with the Perimeter Institute for Theoretical Physics. After a visit to Pennsylvania State University, Luis started projects involving Numerical Relativity, studying Accretion-Induced Collapse of White Dwarfs, also referred to as AIC. Today he is a postdoctoral researcher at Friedrich-Schiller University in Jena, Germany, where he continues his Numerical Relativity work on AIC and kilonova remnants.