Kavli Affiliate: Steven Allen
| First 5 Authors: Chloe Taylor, Daniel Wilkins, Steven Allen, ,
| Summary:
REJ1034+396 is one of the few active galactic nuclei with a significant
quasi-periodic oscillation (QPO). The QPO has been observed in over 1 Ms of
XMM-Newton observations spanning over a decade. We investigate the power
spectral density function (PSD) of 7 long (~90 ks) XMM-Newton observations of
the active galactic nucleus REJ1034+396 in two energy bands. The soft (0.3-0.5
keV) band targets emission from the disk, while the hard (2-7 keV) band
isolates the primary X-ray continuum emission from the corona. The QPO is
significantly detected in the hard band of 5 of the 7 observations. The best
fitting models indicate that the QPO detection in both bands is entirely
attributable to the coronal emission with no additional contribution from the
disk. This explains the strong coherence between the hard and soft bands at the
QPO frequency. The covariance spectrum is consistent with this picture as the
variability at QPO frequencies is attributed solely to fluctuations in the hot
corona. The time lag as a function of energy is well described by a ~2000 s
intrinsic soft lag, resulting from the disk responding to emission from the
corona, that undergoes phase wrapping at approximately the QPO frequency. By
demonstrating that in this system the QPO arises in the corona, we provide new
insights into the mechanisms generating QPOs.
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