Magnetospheres, jets and pulsed emission from compact objects

Seminar
AstroPhysics Seminar
QUEST Center event
No
Speaker
Oliver Porth, University of Amsterdam
Date
25/11/2025 - 13:30 - 12:00Add to Calendar 2025-11-25 12:00:00 2025-11-25 13:30:00 Magnetospheres, jets and pulsed emission from compact objects The time-variable (in particular pulsed-) emission from black holes and neutron stars holds key information on the nature of curved spacetime and ultra dense nuclear matter. However, due to the complex plasma dynamics at play, the interpretation of the observed signals is difficult. I will present some recent work on modeling general relativistic magnetohydrodynamic processes around black holes and accreting neutron stars. I will first discuss the dynamics of strongly perturbed black hole magnetospheres as they can occur for example during binary neutron star merger events. The simulations have revealed a brief 'black-hole pulsar' phase, followed by an intriguing alignment of the magnetic moment and black hole spin which can uniquely imprint the high energy emission of the current sheet. I will further discuss the transient dynamics of multipolar black hole magnetospheres. Switching gears, I will then discuss our recent 3D simulations of accreting neutron stars with oblique magnetospheres, focusing on the questions of jet formation and pulsed emission. The obtained X-ray pulse profiles are consistent in amplitude and harmonic content with the observations of AMXPs, however they also exhibit significant and rapid variability in hotspot temperature and shape due to the turbulent accretion flow.References:[1] S. Selvi, O. Porth, B. Ripperda, and L. Sironi, "Current Sheet Alignment in Oblique Black Hole Magnetospheres: A Black Hole Pulsar?," The Astrophysical Journal, vol. 968, p. L10, Jun. 2024, doi: 10.3847/2041-8213/ad4a5b.[2] P. Das, O. Porth, and A. L. Watts, "GRMHD simulations of accreting neutron stars with non-dipole fields," Monthly Notices of the Royal Astronomical Society, vol. 515, pp. 3144–3161, Sep. 2022, doi: 10.1093/mnras/stac1817.[3] P. Das and O. Porth, "Three-dimensional GRMHD Simulations of Neutron Star Jets," The Astrophysical Journal, vol. 960, p. L12, Jan. 2024, doi: 10.3847/2041-8213/ad151f.[4] P. Das, T. Salmi, J. Davelaar, O. Porth, and A. Watts, "Pulse Profiles of Accreting Neutron Stars from GRMHD Simulations," Nov. 25, 2024, arXiv: arXiv:2411.16528. doi: 10.48550/arXiv.2411.16528.Note: The talk is only over the zoom.https://zoom.us/j/9290951953 Zoom, https://zoom.us/j/9290951953 המחלקה לפיזיקה physics.dept@mail.biu.ac.il Asia/Jerusalem public
Place
Zoom, https://zoom.us/j/9290951953
Abstract

The time-variable (in particular pulsed-) emission from black holes and neutron stars holds key information on the nature of curved spacetime and ultra dense nuclear matter. However, due to the complex plasma dynamics at play, the interpretation of the observed signals is difficult. I will present some recent work on modeling general relativistic magnetohydrodynamic processes around black holes and accreting neutron stars. I will first discuss the dynamics of strongly perturbed black hole magnetospheres as they can occur for example during binary neutron star merger events. The simulations have revealed a brief 'black-hole pulsar' phase, followed by an intriguing alignment of the magnetic moment and black hole spin which can uniquely imprint the high energy emission of the current sheet. I will further discuss the transient dynamics of multipolar black hole magnetospheres. Switching gears, I will then discuss our recent 3D simulations of accreting neutron stars with oblique magnetospheres, focusing on the questions of jet formation and pulsed emission. The obtained X-ray pulse profiles are consistent in amplitude and harmonic content with the observations of AMXPs, however they also exhibit significant and rapid variability in hotspot temperature and shape due to the turbulent accretion flow.

References:
[1] S. Selvi, O. Porth, B. Ripperda, and L. Sironi, "Current Sheet Alignment in Oblique Black Hole Magnetospheres: A Black Hole Pulsar?," The Astrophysical Journal, vol. 968, p. L10, Jun. 2024, doi: 10.3847/2041-8213/ad4a5b.
[2] P. Das, O. Porth, and A. L. Watts, "GRMHD simulations of accreting neutron stars with non-dipole fields," Monthly Notices of the Royal Astronomical Society, vol. 515, pp. 3144–3161, Sep. 2022, doi: 10.1093/mnras/stac1817.
[3] P. Das and O. Porth, "Three-dimensional GRMHD Simulations of Neutron Star Jets," The Astrophysical Journal, vol. 960, p. L12, Jan. 2024, doi: 10.3847/2041-8213/ad151f.
[4] P. Das, T. Salmi, J. Davelaar, O. Porth, and A. Watts, "Pulse Profiles of Accreting Neutron Stars from GRMHD Simulations," Nov. 25, 2024, arXiv: arXiv:2411.16528. doi: 10.48550/arXiv.2411.16528.


Note: The talk is only over the zoom.
https://zoom.us/j/9290951953

תאריך עדכון אחרון : 18/11/2025