Reobserving the NLS1 galaxy RE J1034+396 – I. The long-term, recurrent X-ray QPO with a high significance

ABSTRACT RE J1034+396 is a narrow-line Seyfert 1 galaxy (NLS1) in which the first significant X-ray quasi-periodic oscillation (QPO) in an active galactic nucleus (AGN) was observed in 2007. We report the detection of this QPO in a recent XMM–Newton observation in 2018 with an even higher significance. The quality factor of this QPO is 20, and its period is 3550 ± 80 s, which is 250 ± 100 s shorter than in 2007. While the QPO’s period has no significant energy dependence, its fractional root mean square variability increases from 4 per cent in 0.3–1 keV to 12 per cent in 1–4 keV bands. An interesting phenomenon is that the QPO in 0.3–1 keV leads that in the 1–4 keV bands by 430 ± 50 s with a high coherence, opposite to the soft X-ray lag reported for the observation in 2007. We speculate that the QPO has an intrinsic hard lag, while the previous reported soft lag is caused by the interference of stochastic variability. This soft X-ray lead in the new data supports the idea that the QPO of RE J1034+396 is a possible AGN counterpart of the 67 Hz high-frequency QPO seen in the black hole binary GRS 1915+105. We also search for QPO harmonics, but do not find any significant signals. Our new data reinforce previous results that the QPO is seen in a specific spectral state, as the only two observations showing no significant QPO signal exhibit an even stronger soft X-ray excess than the other six observations that display the QPO. Therefore, our results imply that the QPO in RE J1034+396 is physically linked to a soft X-ray component.

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DETECTION OF A POSSIBLE X-RAY QUASI-PERIODIC OSCILLATION IN THE ACTIVE GALACTIC NUCLEUS 1H 0707–495

The Astrophysical Journal ◽

10.3847/2041-8205/819/2/l19 ◽

2016 ◽

Vol 819 (2) ◽

pp. L19 ◽

Cited By ~ 26

Author(s):

Hai-Wu Pan ◽

Weimin Yuan ◽

Su Yao ◽

Xin-Lin Zhou ◽

Bifang Liu ◽

...

Keyword(s):

Active Galactic Nucleus ◽

Periodic Oscillation ◽

Quasi Periodic Oscillation ◽

X Ray

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DISTINGUISHING BETWEEN SPOT AND TORUS MODELS OF HIGH-FREQUENCY QUASIPERIODIC OSCILLATIONS

Acta Polytechnica ◽

10.14311/ap.2014.54.0191 ◽

2014 ◽

Vol 54 (3) ◽

pp. 191-196 ◽

Cited By ~ 1

Author(s):

Vladimír Karas ◽

Pavel Bakala ◽

Gabriel Török ◽

Michal Dovčiak ◽

Martin Wildner ◽

...

Keyword(s):

High Frequency ◽

Periodic Oscillation ◽

Quasi Periodic Oscillation ◽

X Ray ◽

Bright Spots ◽

Power Spectral ◽

Stable Circular Orbit ◽

Innermost Stable Circular Orbit ◽

Competing Models ◽

Quasiperiodic Oscillations

In the context of high-frequency quasi-periodic oscillation (HF QPOs) we further explore the appearance of an observable signal generated by hot spots moving along quasi-elliptic trajectories close to the innermost stable circular orbit in the Schwarzschild spacetime. The aim of our investigation is to reveal whether observable characteristics of the Fourier power-spectral density can help us to distinguish between the two competing models, namely, the idea of bright spots orbiting on the surface of an accretion torus versus the scenario of intrinsic oscillations of the torus itself. We take the capabilities of the present observatories (represented by the Rossi X-ray Timing Explorer, RXTE) into account, and we also consider the proposed future instruments (represented here by the Large Observatory for X-ray Timing, LOFT).

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Re-observing the NLS1 galaxy RE J1034+396 – II. New insights on the soft X-ray excess, QPO, and the analogy with GRS 1915+105

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3386 ◽

2020 ◽

Vol 500 (2) ◽

pp. 2475-2495

Author(s):

Chichuan Jin ◽

Chris Done ◽

Martin Ward

Keyword(s):

Active Galactic Nucleus ◽

Vertical Structure ◽

Accretion Rate ◽

Timing Analysis ◽

Periodic Oscillation ◽

Phase Lag ◽

Quasi Periodic Oscillation ◽

X Ray ◽

Hot Corona ◽

Physical Analogy

ABSTRACT The active galactic nucleus (AGN) RE J1034+396 displays the most significant X-ray quasi-periodic oscillation (QPO) detected so far. We perform a detailed spectral-timing analysis of our recent simultaneous XMM–Newton, NuSTAR, and Swift observations. We present the energy dependence of the QPO’s frequency, rms, coherence, and phase lag, and model them together with the time-averaged spectra. Our study shows that four components are required to fit all the spectra. These components include an inner disc component (diskbb), two warm corona components (CompTT-1 and CompTT-2), and a hot corona component (nthComp). We find that diskbb, CompTT-2 (the hotter but less luminous component), and nthComp all contain the QPO signal, while CompTT-1 only exhibits stochastic variability. By fitting the lag spectrum, we find that the QPO in diskbb leads CompTT-2 by 679 s, and CompTT-2 leads nthComp by 180 s. By only varying the normalizations, these components can also produce good fits to the time-averaged and variability spectra obtained from previous observations when QPOs were present and absent. Our multiwavelength study shows that the detectability of the QPO does not depend on the contemporaneous mass accretion rate. We do not detect a significant Iron K α emission line, or any significant reflection hump. Finally, we show that the rms and lag spectra in the latest observation are very similar to the 67-Hz QPO observed in the micro-quasar GRS 1915+105. These new results support the physical analogy between these two sources. We speculate that the QPO in both sources is due to the expansion/contraction of the vertical structure in the inner disc.

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