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SUMMARY:PhD Thesis: Attraction and Rejection. On the love-hate relationshi
 p between stars and black holes
DTSTART:20190918T080000Z
DTEND:20190918T110000Z
DTSTAMP:20260817T071000Z
UID:indico-event-6816@indico.fysik.su.se
CONTACT:emanuel.gafton@astro.su.se
DESCRIPTION:Speakers: Emanuel Gafton (Stockholm University\; The Oskar Kle
 in Centre)\n\nSolitary stars wandering too close to the supermassive black
  hole at the centre of their galaxy may become tidally disrupted\,if the t
 idal forces due to the black hole overcome the self-gravity holding the st
 ar together. Depending on the strength of the encounter\, the star may be 
 partially disrupted\, resulting in a surviving stellar core and two tidal 
 arms\, or may be completely disrupted\, resulting in a long and thin tidal
  stream expected to fall back and circularize into an accretion disc.\n\nW
 hile some aspects of a tidal disruption can be described analytically with
  reasonable accuracy\, such an event is the highly non-linear outcome of t
 he interplay between the stellar hydrodynamics and self-gravity\, tidal ac
 celerations from the black hole\, radiation\, potentially magnetic fields 
 and\, in extreme cases\, nuclear reactions. In the vicinity of the black h
 ole\, general relativistic effects become important in determining both th
 e fate of the star and the subsequent evolution of the debris stream.\n\nI
 n this thesis we present a new approach for studying the relativistic regi
 me of tidal disruptions. It combines an exact relativistic description of 
 the hydrodynamical evolution of a test fluid in a fixed curved spacetime w
 ith a Newtonian treatment of the fluid's self-gravity. The method\, though
  trivial to incorporate into existing Newtonian codes\, yields very accura
 te results at minimal additional computational expense.\n\nEquipped with t
 his new tool\, we set out to systematically explore the parameter space of
  tidal disruptions\, focusing on the effects of the impact parameter (desc
 ribing the strength of the disruption) and of the black hole spin on the m
 orphology and energetics of the resulting debris stream. We also study the
  effects of general relativity on partial disruptions\, in order to determ
 ine the range of impact parameters at which partial disruptions occur for 
 various black hole masses\, and the effects of general relativity on the v
 elocity kick imparted to the surviving core. Finally\, we simulate the fir
 st part of a tidal disruption with our code and then use the resulting deb
 ris distribution as input for a grid-based\, general relativistic magnetoh
 ydrodynamics code\, with which we follow the formation and evolution of th
 e resulting accretion disc.\n\nhttps://indico.fysik.su.se/event/6816/
LOCATION:FA31
URL:https://indico.fysik.su.se/event/6816/
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