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

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         Comparing phase-resolved spectroscopy results from QPOs in low-mass X-ray binaries Abigail Stevens, Phil Uttley NAC 2016
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         Low-Mass X-ray Binaries (LMXBs)
         Roche-lobe overflow Accretion disk Compact object Jet Low-mass companion star Figure: ESO/L. Calçada
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         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?
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         Inner Region of an LMXB
         Disk Corona Base of jet ×
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         Inner Region of an LMXB
         Disk Base of jet Corona × Lense-Thirring precession
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         Inner Region of an LMXB
         Disk Base of jet Corona × Lense-Thirring precession
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         Inner Region of an LMXB
         Disk Base of jet Corona × Lense-Thirring precession
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         Inner Region of an LMXB
         Disk Base of jet Corona × Lense-Thirring precession
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         Inner Region of an LMXB
         Disk Base of jet Corona × Lense-Thirring precession
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          Inner Region of an LMXB
          Disk Base of jet Corona × Lense-Thirring precession
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          Inner Region of an LMXB
          Disk Base of jet Corona × Lense-Thirring precession
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          Inner Region of an LMXB
          Disk Base of jet Corona × Lense-Thirring precession
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          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 ×
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          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
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          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
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          Quasi-Periodic Oscillations (QPOs)
          Power spectra show amount of variability at different frequencies in a light curve GX 339-4
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          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)
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          Phase-Resolved Spectroscopy •  New technique allows us to effectively do phase-resolved spectroscopy of QPOs •  Details in paper -- arXiv: 1605.01753
         
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          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°
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          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
         
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          Type B QPO Interpretation
          Jet-like precessing region
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          Type B QPO Interpretation
          Jet-like precessing region
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          Type B QPO Interpretation
          Jet-like precessing region
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          Type B QPO Interpretation
          Jet-like precessing region
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          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
         
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          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 ✉