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SUMMARY:When Stars Refuse to Age Alone: The Physics of Wind–Binary Inter
 action - Leen Decin (KU Leuven)
DTSTART:20260226T123000Z
DTEND:20260226T133000Z
UID:TALK244105@talks.cam.ac.uk
CONTACT:Mika Kontiainen
DESCRIPTION:The dominant uncertainty in late-stage binary evolution is not
  nuclear physics\, but the coupling\nbetween mass loss and orbital dynamic
 s. As low- and intermediate-mass stars evolve along the giant\nbranches\, 
 they develop extended\, pulsation-supported atmospheres and dust-driven wi
 nds with\nsubstantial mass-loss rates. In a binary system\, these outflows
  are generically non-isotropic: the\ncompanion gravitationally focuses the
  wind\, drives spiral shocks\, enables enhanced accretion\, and\nmediates 
 angular momentum exchange through both direct torques and circumbinary res
 ervoirs.\nThe commonly adopted assumption of isotropic\, Jeans-mode mass l
 oss — widely adopted in\npopulation synthesis and secular evolution code
 s — becomes highly questionable in this regime.\n\nIn this talk\, I will
  present a combined observational and 3D radiation–hydrodynamic–chemic
 al\nmodelling approach to quantify the angular momentum budget of evolved 
 binaries. Spatially\nresolved ALMA data constrain the density and velocity
  field of the outflow\, while Hipparcos and\nGaia astrometry constrain orb
 ital architectures. These empirical constraints are coupled to self-\ncons
 istent 3D simulations that resolve wind launching\, gravitational deflecti
 on\, dust formation\, and\ncompanion accretion. By measuring the specific 
 angular momentum carried by the escaping\nmaterial relative to the orbital
  angular momentum\, we can directly assess how mass-loss–driven\ntorques
  modify semi-major axis and eccentricity evolution. This provides a physic
 ally grounded\npathway from resolved flow dynamics to secular orbital evol
 ution\, and challenges the validity of\nclassical isotropic wind prescript
 ions in predicting the fate of interacting giant binaries.\n\nBecause evol
 ved binaries are progenitors of white dwarf pairs\, chemically peculiar st
 ars\, and\ninteracting compact systems\, their physics propagates directly
  into population synthesis\, supernova\nrates\, and galactic chemical enri
 chment. Moreover\, the formation of circumbinary reservoirs links\nthis in
 teraction regime to disk dynamics and potentially to second-generation pla
 net formation.\nUnderstanding how winds couple to orbits is therefore not 
 a specialised problem in stellar\nevolution\, but a key ingredient in trac
 ing how binaries shape stellar populations and galaxies across\ncosmic tim
 e.
LOCATION:Institute of Astronomy 
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