A Synchrotron Self-Compton-Disk Reprocessing Model for Optical/X-Ray Correlation in Black Hole X-Ray Binaries

Veledina, Alexandra; Poutanen, Juri; Vurm, Indrek

doi:10.1088/2041-8205/737/1/l17

Cited by 76 publications

(105 citation statements)

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“…Data on other black hole binaries 33 is currently too insensitive to probe the fast correlation features in question here. Swift J1753.5--0127 can be well explained by synchrotron self--Compton in a hot flow 31 . Consistent with this, the source is known to be radio--quiet with no strong requirement for a jet contributing much to the optical regime 27 .…”

Section: Comparison To Other Sources With Fast Timing Datamentioning

confidence: 94%

An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system

et al. 2017

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Relativistic plasma jets are observed in many accreting black holes. According to theory, coiled magnetic fields close to the black hole accelerate and collimate the plasma, leading to a jet being launched 1-3 . Isolating emission from this acceleration and collimation zone is key to measuring its size and understanding jet formation physics. But this is challenging because emission from the jet base cannot be easily disentangled from other accreting components. Here, we show that rapid optical flux variations from a Galactic black--hole binary are delayed with respect to X--rays radiated from close to the black hole by ~0.1 seconds, and that this delayed signal appears together with a brightening radio jet. The origin of these sub--second optical variations has hitherto been controversial 4-8 . Not only does our work strongly support a jet origin for the optical variations, it also sets a characteristic elevation of ≲10 3 Schwarzschild radii for the main inner optical emission zone above the black hole 9 , constraining both internal shock 10 and magnetohydrodynamic 11 models. Similarities with blazars 12,13 suggest that jet structure and launching physics could potentially be unified under mass--invariant models. Two of the best--studied jetted black hole binaries show very similar optical lags 8,14,15 , so this size scale may be a defining feature of such systems. In June 2015, the Galactic X--ray binary V404 Cygni underwent the brightest outburst of an X-ray binary so far this century. We coordinated simultaneous optical observations from the William Herschel Telescope with X--ray observations from the NuSTAR space observatory on the morning of June 25. These were high frame--rate optical observations taken by the ULTRACAM instrument, sampling timescales down to 35.94 milliseconds (ms). Both optical and X--ray light curves show variability on a broad range of timescales characteristic of this source 15,16 (Fig. 1). The AMI telescope provided contiguous radio coverage throughout this period. Details of the observations may be found in Methods. These coordinated observations occurred on June 25, the day preceding the peak of the 2015 outburst. When the optical observations began, the X--ray intensity was two orders of magnitude below peak, and the spectrum was dominated by low--energy X--rays (i.e., it was in a state characterised as being relatively 'soft'). Steady, compact jet activity is not expected in such a state, and consistent with this, the radio spectral index is negative, as is typical of emission from discrete optically--thin ejecta. NuSTAR observations were interrupted about 2000 seconds later due to a period of Earth occultation, which separates the two halves (hereafter, 'epochs') of the sequence under consideration. At some point during this occultation, the source underwent a dramatic and very rapid change in its X--ray spectral state. When NuSTAR emerged from Earth occultation, the spectrum was instead found to have pivoted towards high energies, with a larger fraction of X--ray counts above 1...

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Section: Comparison To Other Sources With Fast Timing Datamentioning

confidence: 94%

An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system

et al. 2017

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“…There are three possible candidates that may account for this emission: the irradiated disc (Cunningham 1976;Gierliński et al 2009), hot accretion flow (Veledina et al 2013a) and the jet (Hynes et al 2002;Gallo et al 2007). Sometimes the OIR fluxes are higher than expected from any candidate alone (Chaty et al 2003;Gandhi et al 2010), and the complex optical/X-ray cross-correlation functions ⋆ E-mail: juri.poutanen@utu.fi (Kanbach et al 2001;Durant et al 2008) support this anticipation, suggesting contribution of two components simultaneously (Veledina, Poutanen, & Vurm 2011b). The source of OIR emission cannot be determined by only using photometric data and some additional information about the OIR-X-ray connection, short time-scale variability properties and the long-term spectral variations is required (see review in Poutanen & Veledina 2014).…”

Section: Introductionmentioning

confidence: 99%

Colours of black holes: infrared flares from the hot accretion disc in XTE J1550–564

Poutanen

Veledina

Revnivtsev

2014

Monthly Notices of the Royal Astronomical Society

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Outbursts of the black hole (BH) X-ray binaries are dramatic events occurring in our Galaxy approximately once a year. They are detected by the X-ray telescopes and often monitored at longer wavelengths. We analyse the X-ray and optical/infrared (OIR) light-curves of the BH binary XTE J1550-564 during the 2000 outburst. By using the observed extreme colours as well as the characteristic decay time-scales of the OIR and X-ray light curves, we put strong constraints on the extinction towards the source. We accurately separate the contributions to the OIR flux of the irradiated accretion disc and a non-thermal component. We show that the OIR non-thermal component appears during the X-ray state transitions both during the rising and the decaying part of the outburst at nearly the same X-ray hardness but at luminosities differing by a factor of 3. The line marking the quenching/recovery of the non-thermal component at the X-ray hardness-flux diagram seems to coincide with the 'jet line' that marks the presence of the compact radio jet. The inferred spectral shape and the evolution of the non-thermal component during the outburst, however, are not consistent with the jet origin, but are naturally explained in terms of the hybrid hot flow scenario, where non-thermal electrons emit synchrotron radiation in the OIR band. This implies a close, possibly causal connection between the presence of the hot flow and the compact jet. We find that the non-thermal component is hardening during the hard state at the decaying stage of the outburst, which indicates that the acceleration efficiency is a steep function of radius at low accretion rate.

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“…Hence, the spectral model also predicts the connection between the OIR and the X-ray aperiodic variability. However, simultaneous analysis of light curves in these wavelengths (Motch et al 1983;Kanbach et al 2001;Hynes et al 2003;Durant et al 2008;Gandhi et al 2010) has revealed a complicated connection between them, which can be understood if one considers several components contributing to the optical (Veledina et al 2011), namely the hot accretion flow and the reprocessed radiation. Additionally, the jet optically thin synchrotron emission can also be significant (e.g., Casella et al 2010).…”

Section: Introductionmentioning

confidence: 99%

A Unified Lense-Thirring Precession Model for Optical and X-Ray Quasi-Periodic Oscillations in Black Hole Binaries

Veledina

Poutanen

Ingram

2013

ApJ

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Recent observations of accreting black holes reveal the presence of quasi-periodic oscillations (QPO) in the optical power density spectra. The corresponding oscillation periods match those found in X-rays, implying a common origin. Among the numerous suggested X-ray QPO mechanisms, some may also work in the optical. However, their relevance to the broadband-optical through X-ray-spectral properties have not been investigated. For the first time, we discuss the QPO mechanism in the context of the self-consistent spectral model. We propose that the QPOs are produced by Lense-Thirring precession of the hot accretion flow, whose outer parts radiate in optical wavelengths. At the same time, its innermost parts are emitting X-rays, which explains the observed connection of QPO periods. We predict that the X-ray and optical QPOs should be either in phase or shifted by half a period, depending on the observer position. We investigate the QPO harmonic content and find that the variability amplitudes at the fundamental frequency are larger in the optical, while the X-rays are expected to have strong harmonics. We then discuss the QPO spectral dependence and compare the expectations to the existing data.

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A Synchrotron Self-Compton-Disk Reprocessing Model for Optical/X-Ray Correlation in Black Hole X-Ray Binaries

Cited by 76 publications

References 30 publications

An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system

An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system

Colours of black holes: infrared flares from the hot accretion disc in XTE J1550–564

A Unified Lense-Thirring Precession Model for Optical and X-Ray Quasi-Periodic Oscillations in Black Hole Binaries

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