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Abigail Stevens – Comparing origins of low-frequency quasi-periodic oscillations with spectral timing

April 26, 2017 @ 12:00 pm - 1:00 pm

The light curves of low-mass X-ray binaries show variability on timescales from milliseconds to months. The shorter (sub-second) variability is particularly interesting because it is thought to probe the inner region of the accretion disk and the central compact object. X-ray spectral-timing is a new type of analysis that seeks to investigate how matter behaves in the strong gravitational field around the compact object. Observations suggest that different types of low-frequency 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, that are varying possibly due to general relativistic precession. We developed a technique for phase-resolved spectroscopy of QPOs, and are applying it to two types of low-frequency QPOs from the black hole X-ray binary GX 339-4. Over a QPO “period”, we find that the energy spectrum changes not only in normalization, but also in spectral shape. We can quantify how the spectral shape changes as a function of QPO phase, and the two different QPOs show markedly different spectral changes. This talk will feature results from this paper, as well as new preliminary results.


April 26, 2017
12:00 pm - 1:00 pm
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ECAP, room 307
Erwin-Rommel-Str 1
Erlangen, 91058 Germany
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