Nonlinear Dynamics of Spinning Bosonic Stars: Formation and Stability

Area of Science:

• Theoretical physics
• Astrophysics
• Numerical relativity

Background:

• Bosonic stars are hypothetical compact objects formed from scalar fields (boson stars) or vector fields (Proca stars).
• Their formation and stability, particularly when spinning, are crucial for understanding their astrophysical implications.

Purpose of the Study:

• To investigate the formation and stability of spinning bosonic stars using numerical evolutions.
• To compare the behavior of scalar (boson) and vector (Proca) fields in the context of bosonic star formation and stability.

Main Methods:

• Numerical evolutions of the Einstein-Klein-Gordon and Einstein-Proca systems.
• Simulations started with constraint-obeying initial data for dilute, axisymmetric clouds of spinning fields.
• Analysis of stability through nonaxisymmetric perturbations.

Main Results:

• Scalar (boson) stars formed transiently, developing nonaxisymmetric instabilities that ejected angular momentum and led to collapse into spinning black holes.
• Vector (Proca) stars showed no such instabilities, forming stable spinning Proca stars that survived large perturbations.
• Some excited Proca stars decayed to stable fundamental states.

Conclusions:

• Spinning bosonic stars exhibit distinct formation and stability properties depending on the underlying field type (scalar vs. vector).
• Proca stars appear to be stable, unlike boson stars, suggesting different astrophysical roles.
• The observed differences may relate to the toroidal (scalar) versus spheroidal (vector) morphology of these objects.