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Tackling the complexity of Tidal Disruption Events

Project description

Research could shed more light on what happens when a black hole devours a star

When a star gets too close to a supermassive black hole, it experiences an extreme gravitational pull that shreds it into thin streams of material. A portion of the star's mass can be captured into an accretion disk around the black hole, resulting in a temporary bright flash of visible or infrared light. These events are known as tidal disruptions and contain rich information regarding the mechanisms and conditions at play around black holes in otherwise quiescent galaxies. The EU-funded TackTDEs project will investigate how the geometry of the thin gas stream evolves under the influence of the stellar magnetic field and rotation. Furthermore, it will examine how the black hole spin affects the disc formation process.

Objective

When a star gets too close to a supermassive black hole, it gets disrupted by the strong tidal forces of the compact object. A few dozen of these tidal disruption events (TDEs) have been discovered to date and a much larger number is expected from current and near-future missions. The observed signal contains rich information about the mechanisms and conditions at play around black holes in otherwise quiescent galaxies. A full exploitation of the huge predictive power of TDEs urgently requires to improve our understanding of their dynamics and the associated emission. Through a combination of analytical and numerical tools, the proposed research aims at studying the different phases of these events considering crucial physical processes missing from previous investigations. After the star has been disrupted, the debris evolves into an elongated gas stream that partially falls back towards the black hole. The researcher will determine how the geometry of this matter evolves under the influence of stellar magnetic field and rotation. As this stream comes back to pericentre, general-relativistic effects cause it to self-cross, which initiates the formation of an accretion disc and could participate to the emission of TDEs in the optical and UV bands. The researcher will determine the influence of the black hole spin on this process, focusing on the delay of stream-stream collision induced by Lense-Thirring precession. He will also investigate photon diffusion during disc formation to determine the evolution of the emerging shock-powered lightcurve. After the gas has settled, viscous torques drive the accretion of the stellar matter onto the black hole, producing X-ray radiation. The researcher will study this ultimate phase to evaluate the energy output and the origin of angular momentum transport in TDEs. This work will result in great advances in this research field on the theoretical side that will be used to better exploit observational data.

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Coordinator

KOBENHAVNS UNIVERSITET
Net EU contribution
€ 207 312,00
Address
Norregade 10
1165 Kobenhavn
Denmark

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Region
Danmark Hovedstaden Byen København
Activity type
Higher or Secondary Education Establishments
Links
Other funding
€ 0,00