Early time studies of cylindrical liner implosions at 1 MA on COBRA

Atoyan, L.; Byvank, Tom; Cahill, A. D.; Hoyt, C. L.; Grouchy, P. W. L. de; Potter, Walter D.; Kusse, B. R.; Hammer, D. A.

doi:10.1063/1.4904779

Cited by 18 publications

(18 citation statements)

References 3 publications

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“…Blandford & Eichler 1987). Secondly, the number of radio emitting particles is much larger than what is expected in magnetospheric pair production (Kennel & Coroniti 1984b;Atoyan 1999a;Arons & Scharlemann 1979;Timokhin 2010), see also §4.3. (We suggest a way to obtain a hard spectrum, but the multiplicity problem remains.…”

Section: Introductionmentioning

confidence: 99%

Interpreting Crab Nebula’s synchrotron spectrum: two acceleration mechanisms

Lyutikov

Temim

Komissarov

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We outline a model of the Crab Pulsar Wind Nebula with two different populations of synchrotron emitting particles, arising from two different acceleration mechanisms: (i) Component-I due to Fermi-I acceleration at the equatorial portion of the termination shock, with particle spectral index p I ≈ 2.2 above the injection break corresponding to γ wind σ wind ∼ 10 5 , peaking in the UV (γ wind ∼ 10 2 is the bulk Lorentz factor of the wind, σ wind ∼ 10 3 is wind magnetization); (ii) Component-II due to acceleration at reconnection layers in the bulk of the turbulent Nebula, with particle index p II ≈ 1.6. The model requires relatively slow but highly magnetized wind. For both components the overall cooling break is in the infra-red at ∼ 0.01 eV, so that the Component-I is in the fast cooling regime (cooling frequency below the peak frequency). In the optical band Component-I produces emission with the cooling spectral index of α o ≈ 0.5, softening towards the edges due to radiative losses. Above the cooling break, in the optical, UV and X-rays, Component-I mostly overwhelms Component-II. We hypothesize that acceleration at large-scale current sheets in the turbulent nebula (Component-II) extends to the synchrotron burn-off limit of s ∼ 100 MeV. Thus in our model acceleration in turbulent reconnection (Component-II) can produce both hard radio spectra and occasional gamma-ray flares. This model may be applicable to a broader class of high energy astrophysical objects, like AGNe and GRB jets, where often radio electrons form a different population from the high energy electrons. arXiv:1811.01767v3 [astro-ph.HE] 19 Jul 2019 1. In the radio the spectral index is α r = 0.3 (so that νF ν ∝ ν 0.7 ). It is homogeneous over the Nebula (Bietenholz et al. 1997).2. In the infra-red the situation is complicated -a large thermal component from filaments complicates the analysis, see §3.33. In the optical the spectrum softens to α o ∼ 0.6 (so that νF ν ∝ ν 0.4 ).4. The overall spectral distribution of νF ν in the Crab Nebula has a peak in the UV, at ∼ 1 eV. Above the peak the spectrum has α ≈ 1.15. An additional feature present in the hard X-ray spectrum is softening at ∼ 130 keV, with a corresponding break with ∆α = 0.43 (Meyer et al. 2010) (see §2.2 for further discussions)

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Section: Introductionmentioning

confidence: 99%

Interpreting Crab Nebula’s synchrotron spectrum: two acceleration mechanisms

Lyutikov

Temim

Komissarov

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…It moreover imposes constraints on the kind of injected particle's distribution (a power law). This model has been further extended to take partially into account the interaction with the SNR (Reynolds & Chanan 1984;Reynolds & Chevalier 1984), or changes in injection history (Atoyan 1999).…”

Section: -Zone Modelsmentioning

confidence: 99%

Review of the theory of pulsar‐wind nebulae

Bucciantini

2014

Astron Nachr

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Pulsar-wind nebulae (PWNe) are ideal astrophysical laboratories where high energy relativistic phenomena can be investigated. They are close, well resolved in our observations, and the knowledge derived in their study has a strong impact in many other fields, from AGNs to GRBs. Yet there are still unresolved issues, that prevent us from a full clear understanding of these objects. The lucky combination of high resolution X-ray imaging and numerical codes to handle the outflow and dynamical properties of relativistic MHD, has opened a new avenue of investigation that has lead to interesting progressed in the last years. Despite all of these, we do not understand yet how particles are accelerated, and the functioning of the pulsar wind and pulsar magnetosphere, that power PWNe. I will review what is now commonly known as the MHD paradigm, and in particular I will focus on various approaches that have been and are currently used to model these systems. For each I will highlight its advantages and limitations, and degree of applicability.

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“…Despite all of this, we still do not know the origin of the emitting particles, especially the radio emitting ones. This is mainly because we do not know if the nebula is filled by an electronpositron plasma, which will point to an origin of radio emitting particles from the pulsar (Arons 2012), or simply an electron-proton plasma, that will suggest emitting particles come from the environment (Lyutikov 2003;Komissarov 2013) or the supernova (Atoyan 1999). Much of the problem stems from the fact that theoretical models of pair production in pulsar magnetospheres (Hibschman & Arons 2001;Takata, Wang & Cheng 2010;Timokhin & Arons 2013;Takata, Ng & Cheng 2016) under-predict by orders of magnitude the pair multiplicity required by spectral modeling (Bucciantini, Arons & Amato 2011), and this is a common problem even for other PWNe.…”

Section: Introductionmentioning

confidence: 99%

Modeling radio circular polarization in the Crab nebula

Bucciantini

Olmi

2017

Monthly Notices of the Royal Astronomical Society

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In this paper we present, for the first time, simulated maps of the circularly polarized synchrotron emission from the Crab nebula, using multidimensional state of the art models for the magnetic field geometry. Synchrotron emission is the signature of non-thermal emitting particles, typical of many high-energy astrophysical sources, both Galactic and extra-galactic ones. Its spectral and polarization properties allow us to infer key informations on the particles distribution function and magnetic field geometry. In recent years our understanding of pulsar wind nebulae has improved substantially thanks to a combination of observations and numerical models. A robust detection or non-detection of circular polarization will enable us to discriminate between an electron-proton plasma and a pair plasma, clarifying once for all the origin of the radio emitting particles, setting strong constraints on the pair production in pulsar magnetosphere, and the role of turbulence in the nebula. Previous attempts at measuring the circular polarization have only provided upper limits, but the lack of accurate estimates, based on reliable models, makes their interpretation ambiguous. We show here that those results are above the expected values, and that current polarimetric tecniques are not robust enough for conclusive result, suggesting that improvements in construction and calibration of next generation radio facilities are necessary to achieve the desired sensitivity.

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Early time studies of cylindrical liner implosions at 1 MA on COBRA

Cited by 18 publications

References 3 publications

Interpreting Crab Nebula’s synchrotron spectrum: two acceleration mechanisms

Interpreting Crab Nebula’s synchrotron spectrum: two acceleration mechanisms

Review of the theory of pulsar‐wind nebulae

Modeling radio circular polarization in the Crab nebula

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