Magnetic flares and the observed τ[sub T]∼1 in Seyfert Galaxies

Nayakshin, Sergei; Melia, Fulvio

doi:10.1063/1.53943

Cited by 2 publications

(2 citation statements)

References 8 publications

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“…It is interesting to note that recent models for the origin of Xrays in Seyfert Galaxies invoke short-lived and intense magnetic flares on the surface of a cold accretion disk (e.g., Haardt, Ghisellini & Maraschi 1994;Nayakshin & Melia 1997a). In these flares l b > l, since the conditions for plasma confinement require that radiation pressure (the dominant pressure in the case l ≫ 1) is much smaller than the magnetic stress (Nayakshin & Melia 1997b). Therefore, it is very likely that the synchrotron processes keeps the particles thermal in such flares, unless the heating mechanism acts in the opposite direction (the heating mechanism is likely to be of a collective rather than a two-body nature, and it is still unknown; see § 6 below).…”

Section: The Non-maxwellian Parameter Spacementioning

confidence: 99%

Self‐consistent Fokker‐Planck Treatment of Particle Distributions in Astrophysical Plasmas

Nayakshin

Melia

1998

ASTROPHYS J SUPPL S

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High-energy, multi-component plasmas in which pair creation and annihilation, leptonlepton scattering, lepton-proton scattering, and Comptonization all contribute to establishing the particle and photon distributions, are present in a broad range of compact astrophysical objects. The different constituents are often not in equilibrium with each other, and this mixture of interacting particles and radiation can produce substantial deviations from a Maxwellian profile for the lepton distributions. Earlier work has included much of the microphysics needed to account for electron-photon and electron-proton interactions, but little has been done to handle the redistribution of the particles as a result of their Coulomb interaction with themselves. The most detailed analysis thus far for finding the exact electron distribution appears to have been done within the framework of non-thermal models, where the electron distribution is approximated as a thermal one at low energy with a non-thermal tail at higher energy. Recent attention, however, has been focused on thermal models.Our goal here is to use a Fokker-Planck approach in order to develop a fully self-consistent theory for the interaction of arbitrarily distributed particles and radiation to arrive at an accurate representation of the high-energy plasma in these sources. We conduct several tests representative of two dominant segments of parameter space. For high source compactness of the total radiation field, l ∼ 10 2 , we find that although the electron distribution deviates substantially from a Maxwellian, the resulting photon spectra are insensitive to the exact electron shape, in accordance with some earlier results. For low source compactness, l ∼ few, and an optical depth < ∼ 0.2, however, we find that both the electron distribution and the photon spectra differ strongly from what they would be in the case of a Maxwellian distribution. In addition, for all values of compactness, we find that different electron distributions lead to different positron number densities and proton equilibrium temperatures. This means that the ratio of radiation pressure to proton pressure is strongly dependent on the lepton distribution, which might lead to different configurations of hydrostatic equilibrium. This, in turn, may change the compactness, optical depth, and heating and cooling rates, and therefore lead to an additional change in the spectrum. An important result of our analysis, is the derivation of useful, approximate analytical forms for the electron distribution in the case of strongly non-Maxwellian plasmas.

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Section: The Non-maxwellian Parameter Spacementioning

confidence: 99%

Self‐consistent Fokker‐Planck Treatment of Particle Distributions in Astrophysical Plasmas

Nayakshin

Melia

1998

ASTROPHYS J SUPPL S

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“…Therefore their warm layers are also scale independent. Indeed, magnetic flares, perhaps caused by magnetic reconnections in the cold disk, can produce the warm layers in both XRBs and AGNs [156,157].…”

Section: Further Developments On Corona Formationmentioning

confidence: 99%

Black hole binaries and microquasars

Zhang

2013

Front. Phys.

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This is a general review on the observations and physics of black hole X-ray binaries and microquasars, with the emphasize on recent developments in the high energy regime. The focus is put on understanding the accretion flows and measuring the parameters of black holes in them. It includes mainly two parts: (1) Brief review of several recent review article on this subject; (2) Further development on several topics, including black hole spin measurements, hot accretion flows, corona formation, state transitions and thermal stability of standard think disk. This is thus not a regular bottom-up approach, which I feel not necessary at this stage. Major effort is made in making and incorporating from many sources useful plots and illustrations, in order to make this article more comprehensible to non-expert readers. In the end I attempt to make a unification scheme on the accretion-outflow (wind/jet) connections of all types of accreting BHs of all accretion rates and all BH mass scales, and finally provide a brief outlook. PACS numbers: CONTENTS arXiv:1302.5485v1 [astro-ph.HE]

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Magnetic flares and the observed τ[sub T]∼1 in Seyfert Galaxies

Cited by 2 publications

References 8 publications

Self‐consistent Fokker‐Planck Treatment of Particle Distributions in Astrophysical Plasmas

Self‐consistent Fokker‐Planck Treatment of Particle Distributions in Astrophysical Plasmas

Black hole binaries and microquasars

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