Discovery of kHz fluctuations in Centaurus X-3: Evidence for photon bubble oscillations (PBO) and turbulence in a high mass x-ray binary pulsar
The authors report the discovery of kHz fluctuations, including quasi-periodic oscillations (QPO) at {approximately}330 Hz and {approximately}760 Hz and a broadband kHz continuum in the power density spectrum of the high mass X-ray binary pulsar Centaurus X-3 (Jernigan, Klein and Arons 2000). These observations of Cen X-3 were carried out with the Rossi X-ray Timing Explorer (RXTE). The fluctuation spectrum is flat from mHz to a few Hz, then steepens to f{sup {minus}2} behavior between a few Hz and {approximately}100 Hz. Above a hundred Hz, the spectrum shows the QPO features, plus a flat continuum extending to {approximately}1200 Hz and then falling out to {approximately}1800 Hz. Multi-dimensional radiation hydrodynamics simulations of optically thick plasma flow onto a magnetized neutron star show that the fluctuations at frequencies above 100 Hz are the likely consequence of the photon bubble turbulence and oscillations (PBO) previously predicted (Klein et al. 1996) to be observable in this source. The authors show that previous observations of Cen X-3 constrain the models to depend on only one parameter, the size of the polar cap. For a polar cap opening angle of 0.25 radians (polar cap radius {approximately}2.5 km and area {approximately}20 km{sup 2}, for a neutron star radius of 10 km), the authors show that the spectral form above 100 Hz is reproduced by the simulations, including the frequencies of the QPO and the relative power in the QPO and the kHz continuum. This has resulted in the first measurement of the polar cap size of an X-ray pulsar.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Defense Programs (DP) (US)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 756944
- Report Number(s):
- UCRL-JC-134202-REV-1; TRN: AH200025%%55
- Resource Relation:
- Conference: X-Ray Astronomy '99 Conference, Bologne (IT), 09/06/1999--09/10/1999; Other Information: PBD: 1 Sep 1999
- Country of Publication:
- United States
- Language:
- English
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