Astronomy & Astrophysics Seminar

Zoom: https://tau-ac-il.zoom.us/j/87185167411?pwd=FpTUyIgXaOturzOFSetA6pPVYQilen.1

Speaker 1: Oz Amiel

Title: Interface Instabilities of Magnetized Relativistic Jets

Abstract: 

The interaction of relativistic jets with the ambient medium leads to their collimation by the pressure of the surrounding gas. Under such conditions the jet interface may be subject to various types of buoyancy instabilities, which can mix ambient matter into the jet and alter its properties. The exact nature of these instabilities in magnetized jets was not tested rigorously. In this work we run a set of relativistic magnetohydrodynamic simulations to study the growth rate of unstable modes and compare them with the expected linear growth rates, modified for the relativistic case. We show that in jets threaded by a purely poloidal field, interchange modes grow and lead to mixing of heavy baryons into the jet, similar to the effect of the Rayleigh-Taylor instability in the hydrodynamic case. In toroidal fields, magnetic tension stabilizes the jet surface to buoyancy effect, shielding the magnetic jet core from the surroundings. We discuss the implications of our study on realistic astrophysical jets. 

Speaker 2: Yarden Eilat

Title: Unveiling Stellar Structure and Anomalies in Gaia RVS Spectra:

Gaia DR3 provides nearly a million stellar spectra, offering an unprecedented opportunity to uncover new stellar phenomena. To tackle the challenge of analyzing such a large dataset, we apply unsupervised metric learning, dimensionality reduction, and anomaly detection to identify structure and outliers in the Radial Velocity Spectrometer data. This approach enables systematic exploration of spectral diversity and highlights rare or unexpected features that may point to previously unrecognized stellar behaviors.

Seminar Organizer: Dr. Jonathan Stern