Excitation of Neutron Star Oscillation Modes During Binary Inspiral
Abstract
As a compact binary inspirals due to the emission of gravitational waves, its orbital period decreases continuously down to ∼1 ms, its value at coalescence. During the last part of the inspiral, the two stars are close together and their tidal interactions become strong. Neutron stars have many normal modes whose periods lie in the range swept by the orbital period. Some of these modes are resonantly excited by the tidal force. The amount of energy a mode absorbs is proportional to the square of the overlap integral between its displacement field and the tidal force field. For all modes of interest, this overlap is poor, resulting in relatively weak excitation. The absorbed energy is only a small fraction (≲10-6) of the orbital energy, so the orbital phase shift is too weak to be detected by observations of the gravitational wave signal emitted by the inspiraling binary. However, with displacement amplitudes of excited quadrupole modes ranging up to 0.5% (or more) of the stellar radius, the possibility of a detectable electromagnetic signature cannot be dismissed. Both the periods of the modes and the energy they absorb depend quite strongly on the internal structure of the star. Their observation could shed light on the correct high-density equation of state.
- Publication:
-
The Evolution of X-ray Binariese
- Pub Date:
- January 1994
- DOI:
- 10.1063/1.45964
- Bibcode:
- 1994AIPC..308..311R
- Keywords:
-
- 97.60.Jd;
- 97.10.Sj;
- 97.80.Fk;
- 95.30.Sf;
- Neutron stars;
- Pulsations oscillations and stellar seismology;
- Spectroscopic binaries;
- close binaries;
- Relativity and gravitation