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Gabriel Török *

3:2 controversy … hope for underlying QPO physics ?. Gabriel Török *. *Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo nám. 13, CZ-74601 Opava, Czech Republic. The p resentation draws mainly from a collaboration with

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Gabriel Török *

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  1. 3:2 controversy …hope for underlying QPO physics ? Gabriel Török* *Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo nám. 13, CZ-74601 Opava, Czech Republic The presentation draws mainly from a collaboration with M.A. Abramowicz, D. Barret, P.Bakala, M. Bursa, J. Horák, W. Kluzniak, M. Urbanec, and Z. Stuchlík

  2. 1.1.X-ray timing observations of low mass X-ray binaries LMXBs short-term X-ray variability Sco X-1 power • Low frequency QPOs (up to 100Hz) • hecto-hertz QPOs (100-200Hz) • kHz QPOs (~200-1500Hz) frequency Figs on this page:nasa.gov

  3. 1.2.kHz Quasiperiodic oscillations: BH and NS Neutron stars Upper QPO frequency Black holes (microquasars) Lower QPO frequency

  4. 1.3.Ratio clustering Neutron stars Abramowicz et al. (2003), A&A Upper QPO frequency Lower QPO frequency

  5. 1.3.Ratio clustering Histograms of frequency ratio for observations displaying two significant kHz QPOs (Abramowicz et al 2005) in six atoll sources.Histograms peaks close to 3:2 5:4 3:2 5:4 3:2 3:2 4:3 4:3

  6. 2. 3:2 controversy ?? Belloni et al. (2004,2005A&A) studied frequency distributions in several sources. They confirmed the clustering around 3:2 and other ratios, but put some doubts on its interpretation. Consequently, Belloni et al. (2007,MNRAS) examined lower QPO frequency distibution in the atoll source 4U 1636-53 and assuming a linear correlation between lower and upper kHz QPO frequency discussed the inferred ratio dstribution. They concluded that there is no preferred ratio in the source. This result contradicts previous finding of ratio clustering in 1636-53.

  7. 2.2Exploring 4U 1636-53 kHz QPO data The observational data we use here correspond to all the RXTE observations of the atoll source 4U 1636+53 proceeded by the shift-add technique through continuous segments of observation (the analysis of Barret et al. 2005). The part of data displaying significant twin peak QPOs is restricted to about 20 hours of observation.

  8. 2.2Exploring 4U 1636-53 kHz QPO data • The part of data displaying significant twin peak QPOs is restricted to about 20 hours of observation. • The detections of the single significant QPOs extend to about 10 times larger part of observations. • It is possible to determine whether the single peaks belong to group of upper or lower QPOs safely using the Quality factor diagram (Barret 2005). • We have therefore • significant lower QPO detections (lower QPOs) • significant upper QPO detections (upper QPOs) • twin QPOs (overlap between lower and upper QPO observations)

  9. 2.3 Distributions • - significant lower QPO detections (lower QPOs) • significant upper QPO detections (upper QPOs) • twin QPOs (overlap between lower and upper QPO observations) lower QPOs upper QPOs twin QPOs (Torok et al. (2008), AcA submitted)

  10. 2.3 Ratio distribution (Torok et al. (2008), AcA submitted)

  11. 2.4 Resolving the controversy correlation between lower and upper QPO frequency (used by Belloni at al. 2007) Distribution of ratio inferred from lower QPO frequency distibution differs from those inferred from upper and both differe from really observed distribution of ratio. There are the preferred frequency ratios.

  12. 3. Implications for orbital kHz QPO models …hope for underlaying physics ? Figs on this page:nasa.gov

  13. => 3.Implications for orbital models Torok et al. (2008), AcA, accepted For models which identifies given QPO frequency to an orbital radius, one can look from where the oscillations come. Here we focus on the relativistic precession model of Stella and vietri. Ratio radius lower QPOs twin QPOs upper QPOs

  14. 3.Bonus Here we focus on the relativistic precession model of Stella and vietri. lower QPOs twin QPOs upper QPOs Difference between lower and upper QPO amplitude [%] Torok (2008), A&A, submitted

  15. 4. References Figs on this page:nasa.gov

  16. 5. References • Abramowicz et al., A&A L, 2003 • Barret et al., 2005, MNRAS • Belloni et al., 2005, A&A • Mendez, 2006, MNRAS • Belloni et al., 2007, MNRAS • Torok, 2007, A&A L, submitted Presentation download: www.physics.cz/research in sect. news SLIDE UNDER THE CONSTRUCTION

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