The blazar GB 1428+4217: a warm absorber at z = 4.72?

Fabian, A. C.; Celotti, A.; Iwasawa, K.; Ghisellini, G.

doi:10.1046/j.1365-8711.2001.04348.x

Cited by 38 publications

(45 citation statements)

References 19 publications

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“…Previous X‐ray observations have suggested the presence of soft X‐ray spectral flattening 1 in some radio‐loud quasars at redshifts z = 2–3 (Wilkes et al 1992; Elvis et al 1994; Cappi et al 1997; Fiore et al 1998; Yuan & Brinkmann 1999; Reeves & Turner 2000). This result is strengthened and extended to higher redshifts by its detection in a few extremely X‐ray/radio‐loud quasars at z > 4, namely RX J1028.6 – 0844 (Yuan et al 2000), GB 1428 + 4217 (Boller et al 2000; Fabian et al 2001b), and PMN J0525 − 3343 (Fabian et al 2001a), with ROSAT , ASCA , and BeppoSAX . These object seem to have characteristics typical of blazars (Fabian et al 1997, 1998; Zickgraf et al 1997; Moran & Helfand 1997; Hook & McMahon 1998).…”

Section: Introductionmentioning

confidence: 76%

“…The most plausible explanation for this effect is photoelectric absorption of soft X‐rays by an associated medium with column densities of 10 22–23 cm −2 , although intrinsic spectral flattening cannot be excluded. The physical implication of this effect has been discussed extensively in the literature in terms of excess absorption (Elvis et al 1998; Yuan et al 2000; Fabian et al 2001a,b) and intrinsic breaks in the X‐ray spectra of blazars (Fabian et al 2001a,b).…”

Section: Introductionmentioning

confidence: 99%

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XMMobservations of the high-redshift quasar RX J1028.6 - 0844 atz= 4.276: soft X-ray spectral flattening

Yuan¹,

Fabian²,

Celotti³

et al. 2005

Monthly Notices of the Royal Astronomical Society

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We present results from a new XMM–Newton observation of the high‐redshift quasar RX J1028.6 – 0844 at a redshift of 4.276. The soft X‐ray spectral flattening, as reported by a previous study with ASCA, is confirmed to be present, with, however, a reduced column density when modelled by absorption. The inferred column density for absorption intrinsic to the quasar is 2.1(+0.4−0.3) × 1022 cm−2 for cold matter, and higher for ionized gas. The spectral flattening shows remarkable similarity with that of two similar object, namely GB 1428 + 4217 and PMN J0525 − 3343. The results improve upon those obtained from a previous short‐exposure observation for RX J1028.6 – 0844 with XMM–Newton. A comparative study of the two XMM–Newton observations reveals a change in the power‐law photon index from Γ≃ 1.3 to 1.5 on time‐scales of about one year. A tentative excess emission feature in the rest‐frame 5–10 keV band is suggested, which is similar to that marginally suggested for GB 1428 + 4217.

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Section: Introductionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

XMMobservations of the high-redshift quasar RX J1028.6 - 0844 atz= 4.276: soft X-ray spectral flattening

Yuan¹,

Fabian²,

Celotti³

et al. 2005

Monthly Notices of the Royal Astronomical Society

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“…According to our model, the peak of the high‐energy hump of the SED during the Beppo SAX observations (Fabian et al 2001) is predicted to lie at ∼1 MeV, locating this source at one extreme of the blazar sequence. The model assumes a black hole mass M = 1.5 × 10 9 M ⊙ , an accretion disc emitting at ∼2/3 of the Eddington ratio (the other third is emitted by the X‐ray corona).…”

Section: Some Illustrative Examplesmentioning

confidence: 87%

“… Top panel: the SED of one of the most distant blazars, together to three different models with different R diss (see Table 1 for the set of parameters) to illustrate possible different states of the source. See Fabian et al (2001) and references therein for the sources of data, and Celotti et al (2007) for further discussion about this source. …”

Section: Some Illustrative Examplesmentioning

confidence: 99%

Canonical high-power blazars

Ghisellini

Tavecchio

2009

Monthly Notices of the Royal Astronomical Society

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538

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The jets of powerful blazars propagate within relatively dense regions of radiation produced externally to the jet. This radiation is a key ingredient to understand the origin of the high‐energy emission of blazars, from the X‐ray to the γ‐ray energy band. The main components contributing to the external radiation field are the accretion disc emission, including its X‐ray corona, the broad‐line region, the infrared emitting torus and the cosmic background radiation. Their importance changes as a function of the distance from the black hole and of the value of the bulk Lorentz factor of the jet. These external radiation fields control the amount of the inverse Compton radiation with respect to the synchrotron flux. Therefore, the predicted spectral energy distribution (SED) will depend on where the jet dissipates part of its energy to produce the observed radiation. We investigate in detail how the SED changes as a function of the location of the jet dissipation region by assuming rather ‘standard’ (i.e. ‘canonical’) prescriptions for the accretion disc and its X‐ray corona, the profile of the jet magnetic field and the external radiation. We confirm that most of the dissipation, if producing the γ‐ray flux we see, must occur at hundreds of Schwarzschild radii from the black hole, to avoid the γ−γ→e± process, and the consequent re‐emission by the produced pairs. The magnetic energy density of a ‘canonical’ jet almost never dominates the radiative cooling of the emitting electrons, and consequently the inverse Compton flux almost always dominates the bolometric output. This is more so for large black hole masses. Dissipation taking place beyond the broad‐line region is particularly interesting, since it accounts in a simple way for the largest inverse Compton to synchrotron flux ratios accompanied by an extremely hard X‐ray spectrum. Furthermore, it makes the high‐power blazars at high redshift useful tools to study the optical to UV cosmic backgrounds.

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“…the location of the peak 1 Fossati et al (1998) showed that blazar SEDs seem to change systematically with luminosity; the most powerful objects are red, while blue SEDs are associated with relatively weak sources, a result supported by studies of high‐redshift blazars and of low‐power BL Lac objects (see Costamante et al 2001; Fabian et al 2001a,b; Ghisellini et al 2010).…”

Section: Introductionmentioning

confidence: 94%

Time-dependent simulations of multiwavelength variability of the blazar Mrk 421 with a Monte Carlo multizone code

Chen¹,

Fossati²,

Liang³

et al. 2011

Monthly Notices of the Royal Astronomical Society

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We present a new time‐dependent multizone radiative transfer code and its first application to study the synchrotron self‐Compton (SSC) emission of the blazar Mrk 421. The code couples Fokker–Planck and Monte Carlo methods in a two‐dimensional (cylindrical) geometry. For the first time all the light traveltime effects (LTTE) are fully considered, along with a proper, full, self‐consistent treatment of Compton cooling, which depends on them. We study a set of simple scenarios where the variability is produced by injection of relativistic electrons as a ‘shock front’ crosses the emission region. We consider emission from two components, with the second component either being pre‐existing and cospatial and participating in the evolution of the active region (background), or being spatially separated and independent, only diluting the observed variability (foreground). Temporal and spectral results of the simulation are compared to the multiwavelength observations of Mrk 421 in 2001 March. We find parameters that can adequately fit the observed SEDs and multiwavelength light curves and correlations. There remain, however, a few open issues, most notably (i) the simulated data show a systematic soft intraband X‐ray lag, (ii) the quadratic correlation between the TeV γ‐ray and X‐ray flux during the decay of the flare has not been reproduced. These features turned out to be among those more affected by the spatial extent and geometry of the source, i.e. LTTE. The difficulty of producing hard X‐ray lags is exacerbated by a bias towards soft lags caused by the combination of energy‐dependent radiative cooling time‐scales and LTTE. About the second emission component, our results strongly favour the scenario where it is cospatial and it participates in the flare evolution, suggesting that different phases of activity may occur in the same region. The cases presented in this paper represent only an initial study, and despite their limited scope they make a strong case for the need of true time‐dependent and multizone modelling.

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The blazar GB 1428+4217: a warm absorber at z = 4.72?

Cited by 38 publications

References 19 publications

XMMobservations of the high-redshift quasar RX J1028.6 - 0844 atz= 4.276: soft X-ray spectral flattening

XMMobservations of the high-redshift quasar RX J1028.6 - 0844 atz= 4.276: soft X-ray spectral flattening

Canonical high-power blazars

Time-dependent simulations of multiwavelength variability of the blazar Mrk 421 with a Monte Carlo multizone code

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