Speaker
Description
Low frequency quasi-periodic oscillations (QPO) with periods between ~10 s and ~0.05 s are often seen in the X-ray flux of accreting stellar-mass black holes. These are often attributed to the Lense-Thirring precession of the inner accretion flow, a General Relativistic effect caused by the spin of the black hole.
QPO phase-resolved spectroscopy, i.e. measuring how the X-ray spectrum changes with QPO phase, provides the best test of this model against alternative interpretations, since precession will lead to a rocking of the ~6.4 keV iron fluorescence line between Doppler red and blue shift over the course of each QPO cycle. We present a QPO phase-resolved spectral analysis of the bright black hole X-ray binary system GRS 1915+105 utilising simultaneous data from NICER and NuSTAR, using a novel method to track changes in the QPO centroid frequency during the course of the observation. The very high count rate and very broad band X-ray coverage (~0.3-79 keV) provided by the combination of NICER and NuSTAR makes this an ideal dataset for our analysis.
| Affiliation | University of Oxford |
|---|---|
| Topic | Multi-messenger and transient astronomy |
