Secular Instabilities in Rotating Relativistic Stars and Their Nonlinear Dynamical Natures

2014 Fiscal Year Final Research Report

• Project/Area Number: 23740201
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Waseda University (2013-2014); Rikkyo University (2011-2012)
• Principal Investigator: SAIJO Motoyuki 早稲田大学, 教育・総合科学学術院, 助教 (40510988)
• Project Period (FY): 2011-04-28 – 2015-03-31
• Keywords: 相対論的回転星 / 流体動力学 / 航空工学的な近似 / 重力波 / 重力波による輻射反作用力 / rモード不安定性 / 静的な時間スケール / 非線形動力学

Outline of Final Research Achievements

We have investigated nonlinear r-mode instabilities in uniformly rotating stars, triggered by gravitational radiation reaction force, restored by Coriolis force. First we have succeeded in developing our new computational code of three dimensional hydrodynamics in Newtonian gravity with mass-current multipole of radiation reaction force in rotating reference frame, imposing nonlinear anelastic approximation. In order to verify our developed code, we compare the characteristic frequency and growth timescale of r-mode instability with that from linear perturbation analysis, and have a good agreement. Next we have studied the saturation amplitude of r-mode instabilities in nonlinear anelastic approximation and compared the amplitude with that from three dimensional hydrodynamics. Remarkably we find quite a good agreement within 10 percent in the amplitude, which reinforces studying nonlinear regime of r-mode instabilities with nonlinear anelastic approximation.

Free Research Field

宇宙物理学