Light Echoes in Kerr Geometry: A Source of High‐Frequency QPOs from Random X‐Ray Bursts

Fukumura, Keigo; Kazanas, Demosthenes

doi:10.1086/587159

Cited by 13 publications

(13 citation statements)

References 28 publications

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“…Iguchi et al 2010) and X-ray binaries (e.g. Fukumura & Kazanas 2008;Fukumura et al 2009). We extended the light-house model proposed in Camenzind & Krockenberger (1992) which was applied to simulate optical light curves from BL Lac objects and quasars.…”

Section: Discussionmentioning

confidence: 99%

Kinematics of and Emission From Helically Orbiting Blobs in a Relativistic Magnetized Jet

Mohan

Mangalam

2015

ApJ

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We present a general relativistic (GR) model of jet variability in active galactic nuclei due to orbiting blobs in helical motion along a funnel or cone shaped magnetic surface anchored to the accretion disk near the black hole. Considering a radiation pressure driven flow in the inner region, we find that it stabilizes the flow, yielding Lorentz factors ranging between 1.1 and 7 at small radii for reasonable initial conditions. Assuming these as inputs, simulated light curves (LCs) for the funnel model include Doppler and gravitational shifts, aberration, light bending, and time delay. These LCs are studied for quasi-periodic oscillations (QPOs) and the power spectral density (PSD) shape and yield an increased amplitude (∼ 12 %); a beamed portion and a systematic phase shift with respect to that from a previous special relativistic model. The results strongly justify implementing a realistic magnetic surface geometry in Schwarzschild geometry to describe effects on emission from orbital features in the jet close to the horizon radius. A power law shaped PSD with a typical slope of −2 and QPOs with timescales in the range of (1.37 − 130.7) days consistent with optical variability in Blazars, emerges from the simulations for black hole masses M • = (0.5 − 5) × 10 8 M and initial Lorentz factors γ jet,i = 2 − 10. The models presented here can be applied to explain radio, optical, and X-ray variability from a range of jetted sources including active galactic nuclei, X-ray binaries and neutron stars.

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Section: Discussionmentioning

confidence: 99%

Kinematics of and Emission From Helically Orbiting Blobs in a Relativistic Magnetized Jet

Mohan

Mangalam

2015

ApJ

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“…Several interesting aspects related to the compact objects in these systems could be investigated: -The distinction whether the compact object has a solid surface or is a black hole: a blob of matter spiraling into the event horizon of a black hole would produce a series of progressively weaker flares, whereas accretion onto a neutron star would end in a final bright flash when the matter hits its surface [12,37]. -Measurement of the black hole spin: Fukumura & Kanzanas [38] propose that photons emitted inside the ergosphere can orbit a rapidly rotating black hole. After leaving the vicinity of the black hole, they may arrive at a distant observer as double or triple flares, separated by constant time lags, which is connected to the spin of the black hole.…”

Section: Discussionmentioning

confidence: 99%

Capability of Cherenkov telescopes to observe ultra-fast optical flares

Deil

Domainko

Hermann

et al. 2009

Astroparticle Physics

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PACS: 95.55.Ka 95.55.Qf 95.75.Wx 97.80.Jp Keywords:Ultra-fast optical photometry Cherenkov telescope a b s t r a c tThe large optical reflector ($100 m 2 ) of a H.E.S.S. Cherenkov telescope was used to search for very fast optical transients of astrophysical origin. Forty-three hours of observations targeting stellar-mass black holes and neutron stars were obtained using a dedicated photometer with microsecond time-resolution. The photometer consists of seven photomultiplier tube pixels: a central one to monitor the target and a surrounding ring of six pixels to veto background events. The light curves of all pixels were recorded continuously and were searched offline with a matched-filtering technique for flares with a duration of 2 ls-100 ms. As expected, many unresolved (<3 ls) and many long (>500 ls) background events originating in the earth's atmosphere were detected. In the time range 3-500 ls the measurement is essentially background-free, with only eight events detected in 43 h; five from lightning and three presumably from a piece of space debris. The detection of flashes of brightness $0.1 Jy and only 20 ls duration from the space debris shows the potential of this setup to find rare optical flares on timescales of tens of microseconds. This timescale corresponds to the light crossing time of stellar-mass black holes and neutron stars.

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“…With this in mind we present the corresponding ACFs of both LCs in Figure 4. It can be seen these are drastically different; in fact the ACF of the first light curve is different from of the ACFs of any of the sources presented in this paper despite the presence of strong QPO in all: it consists of two narrow peaks at τ = 0 (self-correlation) and τ ≃ 14 sec, a well known characteristic of an echo in the signal (Fukumura & Kazanas 2008, Fukumura, Kazanas, & Stephenson 2009, albeit of a lag much larger than the one specific to these references). The ACF of GRS 1915+105 does exhibit a (clearly non-sinusoidal) oscillation at the fundamental QPO period (as one would expect from an oscillating source) but, as discussed above, it decreases linearly with time to zero at a lag equal to As an additional argument for the complementary nature of the time and frequency domain analysis, we note that the long term oscillatory nature of the ACF in three of our sources, i.e.…”

Section: The Power Spectrum -Autocorrelation Synergymentioning

confidence: 53%

“…We have recently shown the possibility of (harmonically spaced) "echo" QPOs due to general relativistic frame-dragging in the (simulated) inherently aperiodic LCs of rapidly rotating black holes (i.e. black holes with a/M > ∼ 0.94 where a is specific spin and M is mass of a black hole) (Fukumura & Kazanas 2008,Fukumura, Kazanas, & Stephenson 2009. At this point it is not clear whether any of the observed GBHCs exhibit these "ergospheric" (or any other type of echo) QPOs (there is a search of the existing data bases going on).…”

Section: Introductionmentioning

confidence: 99%

QPOs in the time domain: an autocorrelation analysis

Fukumura

Shrader

Dong

et al. 2010

A&A

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Context. Motivated by the recent proposal that one can obtain quasi-periodic oscillations (QPOs) by photon echoes manifesting as non-trivial features in the autocorrelation function (ACF), we study the ACFs of the light curves of three accreting black hole candidates and a neutron star already known to exhibit QPOs namely, GRS 1915+105, XTE J1550-564, XTE J1859+226 and Cygnus X-2. Aims. We present a comparative study of the timing properties of these systems in the frequency and time domain in search for similarities/differences that may provide clues to the physics underlying the QPO phenomenon. Methods. We compute and focus on the form of the ACFs in search of systematics or specific temporal properties at the time scales associated with the known QPO frequencies in comparison with the corresponding PDS. Results. Even within our small object sample we find both similarities as well as significant and subtle differences in the form of the ACFs both amongst black holes and between black holes and neutron stars to warrant a closer look at the QPO phenomenon in the time domain: the QPO features manifest as an oscillatory behavior of the ACF at lags near zero; the oscillation damps exponentially on time scales equal to the inverse QPO width to a level of a percent or so. In black holes this oscillatory behavior is preserved and easily discerned at much longer lags while this is not the case for the neutron star system Cyg X-2. The ACF of GRS 1915+105 provides an exception to this general behavior in that its decay is linear in time indicating an undamped oscillation of coherent phase. We present simple ad hoc models that reproduce these diverse time domain behaviors and we speculate that their origin is the phase coherence of the underlying oscillation.Conclusions. It appears plausible that time domain analyses, complementary to the more common frequency domain ones, could impose tighter constraints and provide clues for the driving mechanisms behind the QPO phenomenon.

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Light Echoes in Kerr Geometry: A Source of High‐Frequency QPOs from Random X‐Ray Bursts

Cited by 13 publications

References 28 publications

Kinematics of and Emission From Helically Orbiting Blobs in a Relativistic Magnetized Jet

Kinematics of and Emission From Helically Orbiting Blobs in a Relativistic Magnetized Jet

Capability of Cherenkov telescopes to observe ultra-fast optical flares

QPOs in the time domain: an autocorrelation analysis

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