Physics of Pair Producing Gaps in Black Hole Magnetospheres

Chen, Alexander Y.; Yuan, Yajie; Yang, Huan

doi:10.3847/2041-8213/aad8ab

Cited by 45 publications

(43 citation statements)

References 32 publications

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“…4. The screening of the gap occurs in the low-E 0 (Thomson) regime (see crossover of the red and dashed grey lines) and the peak electric field is predicted to be E 0 ∼ 5×10 −3 statV cm −1 ∼ 5×10 −5 B 0 for B 0 = 100 G, consistent with the estimation by Chen et al (2018). In reality, the properties of the radiation field at the gap (e.g., U ph and ǫ min ) are highly uncertain.…”

Section: Application To M87supporting

confidence: 86%

Inverse Compton Cascades in Pair-producing Gaps: Effects of Triplet Pair Production

Πετροπούλου

Yuan

Chen

et al. 2019

ApJ

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Inverse Compton-pair cascades are initiated when gamma-rays are absorbed on an ambient soft photon field to produce relativistic pairs, which in turn up-scatter the same soft photons to produce more gamma-rays. If the Compton scatterings take place in the deep Klein-Nishina regime, then triplet pair production (eγ b → ee + e − ) becomes relevant and may even regulate the development of the cascade. We investigate the properties of pair-Compton cascades with triplet pair production in accelerating gaps, i.e., regions with an unscreened electric field. Using the method of transport equations for the particle evolution, we compute the growth rate of the pair cascade as a function of the accelerating electric field in the presence of black-body and power-law ambient photon fields. Informed by the numerical results, we derive simple analytical expressions for the peak growth rate and the corresponding electric field. We show that for certain parameters, which can be realized in the vicinity of accreting supermassive black holes at the centers of active galactic nuclei, the pair cascade may well be regulated by inverse Compton scattering in the deep Klein-Nishina regime and triplet pair production. We present indicative examples of the escaping gamma-ray radiation from the gap, and discuss our results in application to the TeV observations of radio galaxy M87.

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Section: Application To M87supporting

confidence: 86%

Inverse Compton Cascades in Pair-producing Gaps: Effects of Triplet Pair Production

Πετροπούλου

Yuan

Chen

et al. 2019

ApJ

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“…One can also include dissipative processes explicitly in the GRMHD models, including scalar resistivity (Palenzuela et al 2009;Dionysopoulou et al 2013;Del Zanna et al 2016;Qian et al 2017;Ripperda et al 2019), heat fluxes and viscosities (pressure anisotropies; Chandra et al 2015;Ressler et al 2015;Foucart et al 2017), and particle acceleration (e.g., Chael et al 2017). Ultimately special and general relativistic particle-in-cell codes (Watson & Nishikawa 2010;Chen et al 2018;Levinson & Cerutti 2018;Parfrey et al 2019) will enable direct investigations of kinetic processes.…”

Section: Nonthermal Electronsmentioning

confidence: 99%

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

Akiyama¹,

Alberdi²,

Alef³

et al. 2019

ApJL

1,002

447

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The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing of synchrotron emission from a hot plasma orbiting near the black hole event horizon. The ring radius and ring asymmetry depend on black hole mass and spin, respectively, and both are therefore expected to be stable when observed in future EHT campaigns. Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity. If the black hole spin and M87's large scale jet are aligned, then the black hole spin vector is pointed away from Earth. Models in our library of non-spinning black holes are inconsistent with the observations as they do not produce sufficiently powerful jets. At the same time, in those models that produce a sufficiently powerful jet, the latter is powered by extraction of black hole spin energy through mechanisms akin to the Blandford-Znajek process. We briefly consider alternatives to a black hole for the central compact object. Analysis of existing EHT polarization data and data taken simultaneously at other wavelengths will soon enable new tests of the GRMHD models, as will future EHT campaigns at 230 and 345 GHz.

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“…In this paper, we assume a plasma loading zone consistent with the mechanism of pair production via γ − γ collisions in a gap at the jet base (Levinson & Rieger 2011;Broderick & Tchekhovskoy 2015;Hirotani & Pu 2016;Chen et al 2018;Chen & Yuan 2019). Another possible source of the high-energy photons is the inner part of the accretion disk, which, as shown by Levinson & Rieger (2011), is not enough to fill the M87 jet with plasma of Goldreich-Julian density.…”

Section: Discussionmentioning

confidence: 99%

Toward a Full MHD Jet Model of Spinning Black Holes. I. Framework and a Split Monopole Example

Huang

Pan

2019

ApJ

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In this paper, we investigate the magnetohydrodynamical structure of a jet powered by a spinning black hole, where electromagnetic fields and fluid motion are governed by the Grad-Shafranov equation and the Bernoulli equation, respectively. Assuming steady and axisymmetric jet structure, the global solution is uniquely determined with prescribed plasma loading into the jet and the poloidal shape of the outmost magnetic field line. We apply this model to the jet in the center of nearby radio galaxy M87, and we find it can naturally explain the slow flow acceleration and the flow velocity stratification within 10 5 gravitational radii from the central black hole. In particular, we find the extremal black hole spin is disfavored by the flow velocity measurements, if the plasma loading to the jet is dominated by the electron/positron pair production at the jet base.

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Physics of Pair Producing Gaps in Black Hole Magnetospheres

Cited by 45 publications

References 32 publications

Inverse Compton Cascades in Pair-producing Gaps: Effects of Triplet Pair Production

Inverse Compton Cascades in Pair-producing Gaps: Effects of Triplet Pair Production

First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring

Toward a Full MHD Jet Model of Spinning Black Holes. I. Framework and a Split Monopole Example

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