Relation between the Qausi-Periodic Oscillations and the Low-Frequency Noise of GX 5-1 in the Horizontal Branch
Abstract
Ginga observations of quasi-periodic oscillations (QPO) and the low-frequency noise (LFN) from GX 5-1 in its horizontal-branch spectral state are presented. Power spectral fits were attempted using model functions based on simple oscillating shot models. In order to obtain acceptable fits, separate life distribution functions are necessary in the shot models representing QPO and LFN. Furthermore, a larger amplitude of shots is necessary for QPO than for LFN for the longer lifetime shots. A clear second-harmonic peak of QPO was detected. Variations in the powers of QPO and LFN on timescales of 8--256 s were also studied. These variations were significant for all of the timescales studied, and were uncorrelated with each other on timescales shorter than a few tens of seconds, and correlated on longer timescales. From simulations based on a simple shot model, it was found that the variation amplitude and the lack of correlation on short timescales are not inconsistent with the oscillating shot models. A more complex model is necessary to fully explain the observed properties.
- Publication:
-
Publications of the Astronomical Society of Japan
- Pub Date:
- February 1991
- Bibcode:
- 1991PASJ...43..113M
- Keywords:
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- Horizontal Branch Stars;
- Stellar Oscillations;
- X Ray Binaries;
- Harmonics;
- Neutron Stars;
- Power Spectra;
- Stellar Spectra;
- Astrophysics;
- ACCRETION;
- QUASI-PERIODIC OSCILLATIONS;
- X-RAY BINARIES