Insights from Multi-Band Observations (original) (raw)
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The central pc-scale region in blazars: insights from multi-band observations
Proceedings of the International Astronomical Union, 2013
The empirical relations in the black hole-accretion disk-relativistic jet system and physical processes behind these relations are still poorly understood, partly because they operate close to the black hole within the central light year. Very long baseline array (VLBA) provides unparalleled resolution at 15 GHz with which to observe the jet components at sub-milliarcsecond scales, corresponding to sub-pc-scales for local blazars. We discuss the jet inner structure of blazars, location and radiation mechanisms operating in the innermost parsec-scale region of blazars, and evidence for jet-excited broad-line region (BLR) ouflowing downstream the jet. Outflowing BLR can provide necessary conditions for production of high energy emission along the jet between the base of the jet and the BLR and far beyond the BLR as evidenced by recent observations. Flat spectrum quasars and low synchrotron peaked sources are the most likely objects to host the outfllowing BLR. From the γ-ray absorptio...
Signatures of the Disk–Jet Coupling in the Broad-line Radio Quasar 4C+74.26
The Astrophysical Journal
Here we explore the disk-jet connection in the broad-line radio quasar 4C+74.26, utilizing the results of the multiwavelength monitoring of the source. The target is unique in that its radiative output at radio wavelengths is dominated by a moderately-beamed nuclear jet, at optical frequencies by the accretion disk, and in the hard X-ray range by the disk corona. Our analysis reveals a correlation (local and global significance of 96% and 98%, respectively) between the optical and radio bands, with the disk lagging behind the jet by 250 ± 42 days. We discuss the possible explanation for this, speculating that the observed disk and the jet flux changes are generated by magnetic fluctuations originating within the innermost parts of a truncated disk, and that the lag is related to a delayed radiative response of the disk when compared with the propagation timescale of magnetic perturbations along relativistic outflow. This scenario is supported by the re-analysis of the NuSTAR data, modelled in terms of a relativistic reflection from the disk illuminated by the coronal emission, which returns the inner disk radius R in /R ISCO = 35 +40 −16. We discuss the global energetics in the system, arguing that while the accretion proceeds at the Eddington rate, with the accretion-related bolometric luminosity L bol ∼ 9 × 10 46 erg s −1 ∼ 0.2L Edd , the jet total kinetic energy L j ∼ 4 × 10 44 erg s −1 , inferred from the dynamical modelling of the giant radio lobes in the source, constitutes only a small fraction of the available accretion power.
The Inner Jet of the Quasar PKS 1510$-$089 as Revealed by Multi-waveband Monitoring
arXiv (Cornell University), 2010
As part of our comprehensive long-term multi-waveband monitoring of 34 blazars, we followed the activity in the jet of the blazar PKS 1510−089 during major outbursts during the first half of 2009. The most revealing event was a two-month long outburst that featured a number of γ-ray flares. During the outburst, the position angle of optical linear polarization rotated by about 720 • , which implies that a single emission feature was responsible for all of the flares during the outburst. At the end of the rotation, a new superluminal knot (∼ 22c) passed through the "core" seen on 43 GHz VLBA images at essentially the same time as an extremely sharp, high-amplitude γ-ray and optical flare occurred. We associate the entire multi-flare outburst with this knot. The ratio of γ-ray to synchrotron integrated flux indicates that some of the γ-ray flares resulted from inverse Compton scattering of seed photons outside the ultra-fast spine of the jet. Because many of the flares occurred over time scales of days or even hours, there must be a number of sources of IR-optical-UV seed photonsprobably synchrotron emission-surrounding the spine, perhaps in a slower sheath of the jet.
The Jet‐Disk Connection and Blazar Unification
The Astrophysical Journal, 2003
We discuss the relation between the power carried by relativistic jets and the nuclear power provided by accretion, for a group of blazars including FSRQs and BL Lac objects. They are characterized by good quality broad band X-ray data provided by the Beppo SAX satellite. The jet powers are estimated using physical parameters determined from uniformly modelling their spectral energy distributions (SEDs). Our analysis indicates that for Flat Spectrum Radio Quasars the total jet power is of the same order as the accretion power. We suggest that blazar jets are likely powered by energy extraction from a rapidly spinning black hole through the magnetic field provided by the accretion disk.
Recent Progress in Understanding the Large Scale Jets of Powerful Quasars
Galaxies, 2016
Our understanding of the physics of kpc-scale quasar jets had seemed to converge to a paradigm in which these jets are as highly relativistic on the kpc scale as they are on sub-pc scales close to the central black hole. Retaining bulk Lorentz factors (Γ) on the order of 10-20 at these distances implies a jet power comparable to or higher than their Eddington luminosity. We recently started challenging this paradigm, which was put in place to explain the surprisingly bright X-ray emission of the knots of many quasar jets as inverse Compton scattering off the cosmic microwave background (IC/CMB). We have shown that the knot X-ray emission of the archetypical jets 3C 273 and PKS 0637-752 is not due to IC/CMB. With IC/CMB disfavored, an alternative interpretation for the X-rays is synchrotron radiation from a second population of electrons accelerated in situ up to ∼100 TeV. These results are the first step towards resolving the long-standing issue of the nature of the X-ray emission in powerful quasar jets. Comprehensive observational and theoretical work on essentially all X-ray-detected large-scale quasar jets to test the IC/CMB model over a much larger population needs to be done to examine the implications of slower jets that are extremely efficient accelerators. A fascinating case can be made that-contrary to popular belief-the total radiative power of the large-scale jet of these sources is comparable to that of the quasar core. Even more so, the angle-integrated TeV output of these (previously thought TeV-quiet) quasar jets likely makes them the dominant class among active galactic nuclei (AGN), exceeding the TeV production of so-called TeV blazars.
The discjet relation in strong‐lined blazars
Monthly Notices of the Royal …, 2003
The relation between accretion disc (thermal emission) and jet (non-thermal emission) in blazars is still a mystery as, typically, the beamed jet emission swamps the disc even in the ultraviolet band where disc emission peaks. In this paper we estimate the accretion disc component for 136 flat-spectrum radio quasars selected from the Deep X-ray Radio Blazar Survey. We do this by deriving the accretion disc spectrum from the mass and accretion rate onto the central black hole for each object, estimated using the emission line widths and the power emitted from the broad line region. We find that non-thermal emission dominates the optical/UV band of our sources. The thermal component, in fact, is, on average, ∼ 15 per cent of the total and ∼ > 90 per cent of the objects in the sample have a thermal component < 0.5 of the total luminosity. We then estimate the integrated disc and kinetic jet powers and find that, on average, the disc luminosity is ∼ 1 to 20 times the jet power (depending on the uncertainties in the estimation of the latter quantity). A comparison with previous, independent results favours a scenario in which jet and disk powers are of the same order of magnitude. Extraction of energy from a rotating black hole via the "Blandford-Znajek" mechanism fails to explain the estimated jet power in the majority of our sources. Finally, we find that the typical masses for our sources are ∼ 5×10 8 M ⊙ and that, contrary to previous claims, about one quarter of our radio quasars have relatively small (< 3 × 10 8 M ⊙ ) black hole mass.
The accretion disc-jet connection in blazars
Monthly Notices of the Royal Astronomical Society, 2019
The power spectral density (PSD) of the X-ray emission variability from the accretion disccorona region of black hole X-ray binaries and active galactic nuclei has a broken power-law shape with a characteristic break timescale T B. If the disc and the jet are connected, the jet variability may also contain a characteristic timescale related to that of the disc-corona. Recent observations of the blazar Mrk 421 have confirmed the broken power-law shape of the PSD of its jet X-ray variability. We model the time variability of a blazar, in which emitting particles are assumed to be accelerated by successive shock waves flowing down the jet with a varying inter-shock timescale (T IS). We investigate the possible relation between the characteristic timescales in the disc and jet variability based on the above model, along with mathematically and physically simulated disc variability. We find that both the PSD of the jet and disc variability may have a broken power-law shape but the break timescales are not related in general except only in systems with a small range of BH mass. The break in the jet and the disc PSD are connected to the interval between large amplitude outbursts in the jet (T IS) and to the viscous timescale in the disc, respectively. In frequency bands where multiple emission processes are involved or emission is from lower energy particles, the break in the PSD may not be prominent enough for detection.
Monthly Notices of the Royal Astronomical Society, 2000
The black hole X-ray binary XTE J1550-564 was monitored extensively at X-ray, optical and infrared wavelengths throughout its outburst in 2000. We show that it is possible to separate the optical/near-infrared (OIR) jet emission from the OIR disc emission. Focussing on the jet component, we find that as the source fades in the X-ray hard state, the OIR jet emission has a spectral index consistent with optically thin synchrotron emission (α ≈ −0.6 to −0.7, where F ν ∝ ν α ). This jet emission is tightly and linearly correlated with the X-ray flux; L OIR,jet ∝ L 0.98±0.08 X suggesting a common origin. This is supported by the OIR, X-ray and OIR to X-ray spectral indices being consistent with a single power law (α = −0.73). Ostensibly the compact, synchrotron jet could therefore account for ∼ 100 per cent of the X-ray flux at low luminosities in the hard state. At the same time, (i) an excess is seen over the power law decay of the X-ray flux at the point in which the jet would start to dominate, (ii) the X-ray spectrum slightly softens, which seems to be due to a high energy cut-off or break shifting to a lower energy, and (iii) the X-ray rms variability increases. This may be the strongest evidence to date of synchrotron emission from the compact, steady jet dominating the X-ray flux of an X-ray binary. For XTE J1550-564, this is likely to occur within the luminosity range ∼ (2 × 10 −4 -2 × 10 −3 ) L Edd on the hard state decline of this outburst. However, on the hard state rise of the outburst and initially on the hard state decline, the synchrotron jet can only provide a small fraction (∼ a few per cent) of the X-ray flux. Both thermal Comptonization and the synchrotron jet can therefore produce the hard X-ray power law in accreting black holes. In addition, we report a phenomenonological change in the OIR spectral index of the compact jet from possibly a thermal distribution of particles to one typical of optically thin synchrotron emission, as the jet increases in energy over these ∼ 20 days. Once the steady jet is fully formed and the infrared and X-ray fluxes are linearly correlated, the spectral index does not vary (maintaining α = −0.7) while the luminosity decreases by a factor of ten. These quantitative results provide unique insights into the physics of the relativistic jet acceleration process.