STUDYING FREQUENCY RELATIONSHIPS OF KILOHERTZ QUASI-PERIODIC OSCILLATIONS FOR 4U 1636-53 AND Sco X-1: OBSERVATIONS CONFRONT THEORIES
- Physics Department and Center for Astrophysics, Tsinghua University, Beijing 100084 (China)
- Universite de Toulouse (UPS), 118 Route de Narbonne, 31062 Toulouse Cedex 9 (France)
By fitting the frequencies of simultaneous lower and upper kilohertz quasi-periodic oscillations (kHz QPOs) in two prototype neutron star (NS) QPO sources (4U 1636-53 and Sco X-1), we test the predictive power of all currently proposed QPO models. Models predict a linear, power law, or other relationship between the two frequencies. We found that for plausible NS parameters (mass and angular momentum), no model can satisfactorily reproduce the data, leading to very large chi-square values in our fittings. For both 4U 1636-53 and Sco X-1, this is largely due to the fact that the data significantly differ from a linear relationship. Some models perform relatively better but still have their own problems. Such a detailed comparison of data from models enables identification of routes for improving those models further.
- OSTI ID:
- 21567675
- Journal Information:
- Astrophysical Journal, Vol. 726, Issue 2; Other Information: DOI: 10.1088/0004-637X/726/2/74; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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