Space-time modes of relativistic stars

摘要: ABSTRACT The problem of relativistic stellar pulsations is studied in a somewhat ad hoc approx-imation that ignores all fluid motions. This Inverse Cowling Approximation (ICA) ismotivated by two observations: 1) For highly damped (w-mode) oscillations the fluidplays very little role. 2) If motion neglected for polar oscillationmodes becomes similar to axial modes. Using ICA we find modespectrum has features w-mode spectrum full problem. Moreover,in limit superdense stars, be qualitatively simi-lar These results clearly show importance generalrelativity pulsation modes compact and there are whoseexistence do not depend on motions at all; pure “spacetime” modes.Key words: Stars : neutron - Radiation mechanisms: nonthermal 1 INTRODUCTIONThe stars have attained increasinginterest scientific community last four years. Re-cent improved our understanding both thissubject theory general relativity itself. Never-theless, one can easily identify issues far from wellunderstood present time.When Thorne his colleagues established theoryfor three decades ago (Thorne& Campolattaro 1967; 1969), main werenot different well-known ones Newtoniantheory. Compact objects where found oscillate almostexactly frequencies Newtonian predicted.Relativistic effects only gave rise slow damping ofthe pulsation. emission gravitational radiation im-plied oscillation were complex with arelatively tiny imaginary part.The situation recently changed considerably when anew family was found(Kojima 1988; Kokkotas & Schutz 1992). haveno relation known p g-modes the-ory. Rather, this new modes, existence whichwas suggested simple model (Kokkotas S what willfrom now refer as Approximation(ICA). In work, which intended comple-ment studies problem, examine stellarpulsation approximation. major motiva-tion degree involvement generalrelativity. should indicate