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Title: Tracking the evolution of quasi-periodic oscillation in RE J1034+396 using the Hilbert-Huang transform

RE J1034+396, a narrow-line Seyfert 1 active galactic nucleus (AGN), is the first example of AGNs that exhibited a nearly coherent quasi-periodic oscillation (QPO) for the data collected by XMM-Newton in 2007. The spectral behaviors and timing properties of the QPO have been studied since its discovery. We present an analysis of the QPO in RE J1034+396 based on the Hilbert-Huang transform. Comparing with other time-frequency analysis methods, the Hilbert spectrum reveals the variation of the QPO period in great detail. Furthermore, the empirical mode decomposition provides bandpass-filtered data that can be used in the O – C and correlation analysis. We suggest that it is better to divide the evolution of the QPO in this observation into three epochs according to their different periodicities. In addition to the periodicities, the correlations between the QPO periods and corresponding mean count rates are also different in these three epochs. Further examining the phase lags in these epochs, we found no significant phase lags between the soft and hard X-ray bands, which is also confirmed in the QPO phase-resolved spectral analysis. Finally, we discuss the indications of current models including a spotted accretion disk, diskoseismology, and oscillation of shock according to themore » observed time-frequency and spectral behaviors.« less
Authors:
; ; ;  [1]
  1. Graduate Institute of Astronomy, National Central University, Jhongli 32001, Taiwan (China)
Publication Date:
OSTI Identifier:
22356702
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 788; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; COMPARATIVE EVALUATIONS; CORRELATIONS; COUNTING RATES; DECOMPOSITION; EVOLUTION; FREQUENCY ANALYSIS; GALAXY NUCLEI; HARD X RADIATION; OSCILLATIONS; PERIODICITY; SEYFERT GALAXIES; SPECTRA; TIMING PROPERTIES; X-RAY GALAXIES