Comparing phase-resolved spectroscopy results from QPOs in low-mass X-ray binaries

A presentation at the Netherlands Astronomy Conference 2016.

X-ray spectral-timing is a burgeoning field that seeks to investigate how matter behaves in strong gravitational fields. Observations suggest that different types of quasi-periodic oscillations (QPOs) are associated with different emitting-region geometries (e.g. disk-like or jet-like) in the innermost part of the X-ray binary, close to the neutron star or black hole. We developed a technique for phase-resolved spectroscopy of QPOs, and are applying it to a variety of low-frequency QPOs from low-mass X-ray binaries containing black holes or neutron stars. On the QPO time-scale, we find that the energy spectrum changes not only in normalization, but also in spectral shape. In analyzing a variety of signals we will quantify how the spectral shape changes as a function of QPO phase and look for systematic trends between different classes of sources. We can then use these trends to infer the origin of the QPO and its relation to emitting-region geometry in the strong gravity regime.

Transcript

1. 
   
   
   Comparing phase-resolved
   spectroscopy results from QPOs
   in low-mass X-ray binaries
   Abigail Stevens, Phil Uttley
   NAC 2016
   

   View Slide

2. 
   
   
   Low-Mass X-ray Binaries (LMXBs)
   
   
   
   Roche-lobe
   overflow
   Accretion
   disk
   Compact
   object
   Jet Low-mass
   companion
   star
   Figure: ESO/L. Calçada
   

   View Slide

3. 
   
   
   Low-Mass X-ray Binaries (LMXBs)
   
   
   
   Roche-lobe
   overflow
   Accretion
   disk
   Compact
   object
   Low-mass
   companion
   star
   Jet
   Figure: ESO/L. Calçada
   How does matter behave in strong
   gravitational fields?
   

   View Slide

4. 
   
   
   Inner Region of an LMXB
   
   
   
   Disk
   Corona
   Base of jet
   ×
   

   View Slide

5. 
   
   
   Inner Region of an LMXB
   
   
   
   Disk
   Base of jet
   Corona
   ×
   Lense-Thirring precession
   

   View Slide

6. 
   
   
   Inner Region of an LMXB
   
   
   
   Disk
   Base of jet
   Corona
   ×
   Lense-Thirring precession
   

   View Slide

7. 
   
   
   Inner Region of an LMXB
   
   
   
   Disk
   Base of jet
   Corona
   ×
   Lense-Thirring precession
   

   View Slide

8. 
   
   
   Inner Region of an LMXB
   
   
   
   Disk
   Base of jet
   Corona
   ×
   Lense-Thirring precession
   

   View Slide

9. 
   
   
   Inner Region of an LMXB
   
   
   
   Disk
   Base of jet
   Corona
   ×
   Lense-Thirring precession
   

   View Slide

10. 
    
    
    Inner Region of an LMXB
    
    
    
    Disk
    Base of jet
    Corona
    ×
    Lense-Thirring precession
    

    View Slide

11. 
    
    
    Inner Region of an LMXB
    
    
    
    Disk
    Base of jet
    Corona
    ×
    Lense-Thirring precession
    

    View Slide

12. 
    
    
    Inner Region of an LMXB
    
    
    
    Disk
    Base of jet
    Corona
    ×
    Lense-Thirring precession
    

    View Slide

13. 
    
    
    Inner Region of an LMXB
    
    
    
    Disk
    Base of jet
    1700
    1702
    1704
    1706
    1708
    1710
    Time (s)
    Start Time 12339
    7:28:14:566
    Stop Time 12339
    7:29:32:683
    Bin time:
    0.7812E−02 s
    X-ray variability
    Corona
    ×
    

    View Slide

14. 
    
    
    Inner Region of an LMXB
    
    
    
    Disk
    Base of jet
    blackbody
    re-processing
    Corona
    10
    5 20
    0.1 1
    keV2 (Photons cm−2 s−1 keV−1)
    Energy (keV)
    power-law
    

    View Slide

15. 
    
    
    Inner Region of an LMXB
    
    
    
    Disk
    Base of jet
    blackbody
    re-processing
    Corona
    10
    5 20
    0.1 1
    keV2 (Photons cm−2 s−1 keV−1)
    Energy (keV)
    power-law
    1700
    1702
    1704
    1706
    1708
    1710
    Time (s)
    Start Time 12339
    7:28:14:566
    Stop Time 12339
    7:29:32:683
    Bin time:
    0.7812E−02 s
    X-ray variability
    

    View Slide

16. 
    
    
    Quasi-Periodic Oscillations (QPOs)
    
    
    
    Power spectra show amount of variability at
    different frequencies in a light curve
    GX 339-4
    

    View Slide

17. 
    
    
    Type B vs Type C QPOs
    
    
    
    Schnittman, Homan & Miller 2006; Motta et al 2015 (images); Heil et al 2015b
    1 10
    QPO centroid Frequency (Hz)
    2
    4
    6
    8
    10
    12
    14
    Fractional rms (%)
    2
    4
    6
    Fracti
    2
    4
    6
    8
    10
    12
    14
    Fractional rms (%)
    QPO rms (HI)
    QPO rms (LI)
    QPO rms (HI)
    Average QPO rms (HI)
    QPO rms (LI)
    Average QPO rms (LI)
    0.1 1.0 10.0
    QPO centroid Frequency (Hz)
    5
    10
    15
    20
    25
    Fractional rms (%)
    5
    10
    Fracti
    5
    10
    15
    20
    25
    Fractional rms (%)
    QPO rms (HI)
    QPO rms (LI)
    QPO rms (HI)
    Average QPO rms (HI)
    QPO rms (LI)
    Average QPO rms (LI)
    25
    Type B’s:
    stronger face-on
    Type C’s:
    stronger edge-on
    (binary system inclination)
    

    View Slide

18. 
    
    
    Phase-Resolved Spectroscopy
    •  New technique allows us to effectively do
    phase-resolved spectroscopy of QPOs
    •  Details in paper -- arXiv: 1605.01753
    
    
    
    

    View Slide

19. 
    
    
    Phase-Resolved Spectroscopy
    •  New technique allows us to effectively do
    phase-resolved spectroscopy of QPOs
    •  Details in paper -- arXiv: 1605.01753
    •  Deviations from
    mean energy
    spectrum
    •  Spectral shape is
    varying with
    QPO phase!
    
    
    
    10
    5 20
    0 0.5
    keV2 (Photons cm−2 s−1 keV−1)
    Energy (keV)
    0°
    90°
    180°
    270°
    

    View Slide

20. 
    
    
    Type B QPO Spectral Variations
    Parameters that vary:
    1.  PL index
    2.  PL normalization
    3.  BB temperature
    •  Blackbody variation
    is ~0.3 (110°) out of
    phase with power-
    law
    •  Power-law: large
    variation
    •  Blackbody: small
    variation
    
    
    
    

    View Slide

21. 
    
    
    Type B QPO Interpretation
    
    
    
    Jet-like precessing
    region
    

    View Slide

22. 
    
    
    Type B QPO Interpretation
    
    
    
    Jet-like precessing
    region
    

    View Slide

23. 
    
    
    Type B QPO Interpretation
    
    
    
    Jet-like precessing
    region
    

    View Slide

24. 
    
    
    Type B QPO Interpretation
    
    
    
    Jet-like precessing
    region
    

    View Slide

25. 
    
    
    Type C QPO Interpretation
    Stella & Vietri 1998; Fragile & Anninos 2005; Schnittman, Homan & Miller 2006;
    Ingram, Done & Fragile 2009 (image); Ingram & van der Klis 2015; Fragile et al
    2016 submitted; Ingram et al 2016 submitted
    Our preliminary Type C results support a
    disk-like precessing region
    
    
    
    

    View Slide

26. 
    
    
    Summary
    
    
    
    •  X-ray binaries are the best tool to study matter in
    strong gravitational fields
    •  Phase-resolved spectroscopy of QPOs can help
    break degeneracies between physical models
    •  Type B QPO in GX 339—4:
    –  arXiv: 1605.01753
    –  Interpretation: jet-like precessing region
    •  Type C QPO in GX 339—4:
    –  Preliminary work, in prep
    –  Interpretation: disk-like
    precessing region
    GitHub: abigailStev
    Email: A.L.Stevens@uva.nl
    Twitter: @abigailStev
    ✉
    

    View Slide