A Compton Upscattering Model for Soft Lags in the Lower Kilohertz Quasi-periodic Oscillation in 4U 1608−52

Lee, H. C.; Misra, Ranjeev; Taam, Ronald E.

doi:10.1086/319171

Cited by 70 publications

(119 citation statements)

References 19 publications

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“…These trends may be a hint of a general mechanism behind the production of the lags of the QPOs of each group. Lee, Misra & Taam (2001) developed a model that can consistently explain the lag dependence upon energy seen in the lower kHz QPO of 4U 1608-52 with an up-scattering Comptonization model. In that model, the corona and disc temperatures oscillate coherently at the QPO frequency but the primary oscillations take place in the corona with the source of photons responding to the oscillations.…”

Section: Energy Dependencementioning

confidence: 99%

“…Another aspect of the X-ray signal that has received renewed attention in the last few years is the energy-and frequency-dependent time (or phase) lags (e.g., van der Klis et al 1987; Wijers, van Paradijs & Lewin 1987;Mitsuda & Dotani 1989;Vaughan et al 1997b;Kaaret et al 1999;Nowak et al 1999;Lee, Misra & Taam 2001;de Avellar et al 2013;Barret 2013;Kumar & Misra 2014), since they can encode properties of the medium that produces the variability and the radiative processes occurring there.…”

Section: Introductionmentioning

confidence: 99%

“…The mechanisms proposed to explain these lags involve, in general, Compton up-/down-scattering of photons produced in the accretion disc (and in the case of neutron star systems, on the neutron-star surface or boundary layer) in a corona of hot electrons that surrounds the system (see, for example, Sunyaev & Titarchuk 1980;Payne 1980;Lee & Miller 1998;Lee, Misra & Taam 2001;Falanga & Titarchuk 2007, for a discussion about the models).…”

Section: Introductionmentioning

confidence: 99%

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Phase lags of quasi-periodic oscillations across source states in the low-mass X-ray binary 4U 1636–53

Avellar

Méndez

Altamirano

et al. 2016

Mon. Not. R. Astron. Soc.

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While there are many dynamical mechanisms and models that try to explain the origin and phenomenology of the quasi-periodic oscillations (QPOs) seen in the X-ray light curves of low-mass X-ray binaries, few of them address how the radiative processes occurring in these extreme environments give rise to the rich set of variability features actually observed in these light curves. A step towards this end comes from the study of the energy and frequency dependence of the phase lags of these QPOs. Here we used a methodology that allowed us to study, for the first time, the dependence of the phase lags of all QPOs in the range of 1 Hz to 1300 Hz detected in the low-mass X-ray binary 4U 1636-53 upon energy and frequency as the source changes its states as it moves through the colour-colour diagram. Our results suggest that within the context of models of up-scattering Comptonization, the phase lags dependencies upon frequency and energy can be used to extract size scales and physical conditions of the medium that produces the lags.

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Section: Energy Dependencementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phase lags of quasi-periodic oscillations across source states in the low-mass X-ray binary 4U 1636–53

Avellar

Méndez

Altamirano

et al. 2016

Mon. Not. R. Astron. Soc.

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“…Such analysis of high frequency QPOs can give crucial information regarding the size of the emitting region (e.g. Lee, Misra & Taam 2001;Kumar & Misra 2014) and for the low frequency ones the causal connection between spectral parameters (Misra & Mondal 2013). Ingram & van der Klis (2015) have considered both energy dependent rms and phase resolved spectroscopy to argue that the low frequency QPO in the χ state has a geometric origin.…”

Section: Introductionmentioning

confidence: 99%

A model for the energy-dependent time-lag and rms of the heartbeat oscillations in GRS 1915+105

Mir

Misra

Pahari

et al. 2016

Mon. Not. R. Astron. Soc.

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Energy dependent phase lags reveal crucial information about the causal relation between various spectral components and about the nature of the accretion geometry around the compact objects. The time-lag and the fractional root mean square (rms) spectra of GRS 1915+105 in its heartbeat oscillation class/ρ state show peculiar behaviour at the fundamental and harmonic frequencies where the lags at the fundamental show a turn around at ∼ 10 keV while the lags at the harmonic do not show any turn around at least till ∼ 20 keV. The magnitude of lags are of the order of few seconds and hence cannot be attributed to the light travel time effects or Comptonization delays. The continuum X-ray spectra can roughly be described by a disk blackbody and a hard X-ray power-law component and from phase resolved spectroscopy it has been shown that the inner disk radius varies during the oscillation. Here, we propose that there is a delayed response of the inner disk radius (DROID) to the accretion rate such that r in (t) ∝ṁ β (t − τ d ). The fluctuating accretion rate drives the oscillations of the inner radius after a time delay τ d while the power-law component responds immediately. We show that in such a scenario a pure sinusoidal oscillation of the accretion rate can explain not only the shape and magnitude of energy dependent rms and time-lag spectra at the fundamental but also the next harmonic with just four free parameters.

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“…The QPOs occur in the 300 -1200 Hz range and were quickly thought to be associated with orbital frequencies of the inner accretion flow -a characteristic shared by a majority of the models that attempt to explain the origin of kHz QPOs (Miller et al 1998;Stella & Vietri 1999;Lamb & Miller 2001). However, there are models that do not associate the kHz QPOs with the orbital frequencies of the inner acjon.troyer@wayne.edu cretion flow (see e.g., Lee et al 2001;Kumar & Misra 2014, 2016. See van der Klis (2000Klis ( , 2006 for a review of various kHz QPO models.…”

mentioning

confidence: 99%

SPECTRAL-TIMING ANALYSIS OF THE LOWER kHz QPO IN THE LOW-MASS X-RAY BINARY AQUILA X-1

Troyer

Cackett

2017

ApJ

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Spectral-timing products of kilohertz quasi-periodic oscillations (kHz QPOs) in low-mass X-ray binary (LMXB) systems, including energy-and frequency-dependent lags, have been analyzed previously in 4U 1608-52, 4U 1636-53, and 4U 1728-34. Here, we study the spectral-timing properties of the lower kHz QPO of the neutron star LMXB Aquila X-1 for the first time. We compute broadband energy lags, as well as energydependent lags and the covariance spectrum using data from the Rossi X-ray Timing Explorer (RXTE). We find very similar characteristics to other previously studied systems, including soft lags of ∼30 µs between the 3.0 -8.0 keV and 8.0 -20.0 keV energy bands at the average QPO frequency. We also find lags that show a nearly monotonic trend with energy, with the highest energy photons arriving first. The covariance spectrum of the lower kHz QPO is well fit by a thermal Comptonization model, though we find a higher seed photon temperature compared to the mean spectrum, which was also seen in Peille et al. (2015), and indicates the possibility of a composite boundary layer emitting region. Lastly, we see in one set of observations, an Fe K component in the covariance spectrum at 2.4-σ confidence which may raise questions about the role of reverberation in the production of lags.

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A Compton Upscattering Model for Soft Lags in the Lower Kilohertz Quasi-periodic Oscillation in 4U 1608−52

Cited by 70 publications

References 19 publications

Phase lags of quasi-periodic oscillations across source states in the low-mass X-ray binary 4U 1636–53

Phase lags of quasi-periodic oscillations across source states in the low-mass X-ray binary 4U 1636–53

A model for the energy-dependent time-lag and rms of the heartbeat oscillations in GRS 1915+105

SPECTRAL-TIMING ANALYSIS OF THE LOWER kHz QPO IN THE LOW-MASS X-RAY BINARY AQUILA X-1

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