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Title: Modelling jets, tori and flares in pulsar wind nebulae

Abstract

In this contribution we review the recent progress in the modelling of Pulsar Wind Nebulae (PWN). We start with a brief overview of the relevant physical processes in the magnetosphere, the wind-zone and the inflated nebula bubble. Radiative signatures and particle transport processes obtained from 3D simulations of PWN are discussed in the context of optical and X-ray observations. We then proceed to consider particle acceleration in PWN and elaborate on what can be learned about the particle acceleration from the dynamical structures called GwispsG observed in the Crab nebula. We also discuss recent observational and theoretical results of gamma-ray flares and the inner knot of the Crab nebula, which had been proposed as the emission site of the flares. Here, we extend the discussion to GeV flares from binary systems in which the pulsar wind interacts with the stellar wind from a companion star. The chapter concludes with a discussion of solved and unsolved problems posed by PWN.

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8]
  1. Institute for Theoretical Physics, Frankfurt am Main (Germany)
  2. DESY, Zeuthen (Germany)
  3. Univ. degli Studi di Firenze, Sesto F.no (Firenze) (Italy); INFN - Sezione di Firenze, Sesto F.no (Firenze) (Italy); INAF Osservatorio Astrofisico di Arcetri, Firenze (Italy)
  4. Univ. of Leeds, Leeds (United Kingdom)
  5. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  6. Univ. degli Studi di Firenze, Sesto F.no (Firenze) (Italy); INAF Osservatorio Astrofisico di Arcetri, Firenze (Italy)
  7. Princeton Univ., Princeton, NJ (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
  8. Univ. of California, Santa Cruz, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1369251
Grant/Contract Number:
AC02-76SF00515; 610058; TEONGRAV; Fisica dei plasmi relativistici: toeria e appli- cazioni moderne; Research Fellowship; NNX14AH35G; 1411920; 1455342
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Space Science Reviews
Additional Journal Information:
Journal Volume: 207; Journal Issue: 1-4; Journal ID: ISSN 0038-6308
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Porth, Oliver, Buehler, Rolf, Olmi, Barbara, Komissarov, Serguei, Lamberts, Astrid, Amato, Elena, Yuan, Yajie, and Rudy, Alexander. Modelling jets, tori and flares in pulsar wind nebulae. United States: N. p., 2017. Web. doi:10.1007/s11214-017-0344-x.
Porth, Oliver, Buehler, Rolf, Olmi, Barbara, Komissarov, Serguei, Lamberts, Astrid, Amato, Elena, Yuan, Yajie, & Rudy, Alexander. Modelling jets, tori and flares in pulsar wind nebulae. United States. doi:10.1007/s11214-017-0344-x.
Porth, Oliver, Buehler, Rolf, Olmi, Barbara, Komissarov, Serguei, Lamberts, Astrid, Amato, Elena, Yuan, Yajie, and Rudy, Alexander. Wed . "Modelling jets, tori and flares in pulsar wind nebulae". United States. doi:10.1007/s11214-017-0344-x. https://www.osti.gov/servlets/purl/1369251.
@article{osti_1369251,
title = {Modelling jets, tori and flares in pulsar wind nebulae},
author = {Porth, Oliver and Buehler, Rolf and Olmi, Barbara and Komissarov, Serguei and Lamberts, Astrid and Amato, Elena and Yuan, Yajie and Rudy, Alexander},
abstractNote = {In this contribution we review the recent progress in the modelling of Pulsar Wind Nebulae (PWN). We start with a brief overview of the relevant physical processes in the magnetosphere, the wind-zone and the inflated nebula bubble. Radiative signatures and particle transport processes obtained from 3D simulations of PWN are discussed in the context of optical and X-ray observations. We then proceed to consider particle acceleration in PWN and elaborate on what can be learned about the particle acceleration from the dynamical structures called GwispsG observed in the Crab nebula. We also discuss recent observational and theoretical results of gamma-ray flares and the inner knot of the Crab nebula, which had been proposed as the emission site of the flares. Here, we extend the discussion to GeV flares from binary systems in which the pulsar wind interacts with the stellar wind from a companion star. The chapter concludes with a discussion of solved and unsolved problems posed by PWN.},
doi = {10.1007/s11214-017-0344-x},
journal = {Space Science Reviews},
number = 1-4,
volume = 207,
place = {United States},
year = {Wed Mar 22 00:00:00 EDT 2017},
month = {Wed Mar 22 00:00:00 EDT 2017}
}

Journal Article:
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Cited by: 2works
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  • Flows of synchrotron-emitting material can be found in several astrophysical contexts, including extragalactic jets and pulsar-wind nebulae (PWNe). For X-ray synchrotron emission, flow times are often longer than electron radiative lifetimes, so the effective source size at a given X-ray energy is the distance electrons radiating at that energy can convect before they burn off. Since synchrotron losses vary strongly with electron energy, the source size drops with increasing X-ray energy, resulting in a steepening of the synchrotron spectrum. For homogeneous sources, this burnoff produces the well known result of a steepening by 0.5 in the source's integrated spectral index.more » However, for inhomogeneous sources, different amounts of steepening are possible. I exhibit a simple phenomenological picture of an outflow of relativistic electrons with bulk nonrelativistic flow speed, with transverse flow-tube radius, magnetic field strength, matter density, and flow velocity all varying as different powers of distance from the injection point. For such a picture, I calculate the value of the spectral index above the break as a function of the power-law indices, and show the possible range of steepenings. I show that these simple calculations are confirmed by full integrations of source luminosity, which also include the spectral 'bump' below the break from the accumulation of electrons formerly at higher energies. In many cases, extragalactic jets show X-ray synchrotron emission steeper by more than 0.5 than the radio emission; the same phenomenon is exhibited by many PWNe. It is possible that source inhomogeneities are responsible in at least some cases, so that the amount of spectral steepening becomes a diagnostic for source dynamical or geometrical properties.« less
  • The results from a systematic study of 11 pulsar wind nebulae with a torus structure observed with the Chandra X-ray Observatory are presented. A significant observational correlation is found between the radius of the tori, r, and the spin-down luminosity of the pulsars, E-dot. A logarithmic linear fit between the two parameters yields log r = (0.57 +- 0.22) log E-dot-22.3 +- 8.0 with a correlation coefficient of 0.82, where the units of r and E-dot are pc and ergs s{sup -1}, respectively. The value obtained for the E-dot dependency of r is consistent with a square-root law, which ismore » theoretically expected. This is the first observational evidence of this dependency, and provides a useful tool to estimate the spin-down energies of pulsars without direct detections of pulsation. Applications of this dependency to some other samples are also shown.« less
  • It has been suggested that some classes of luminous supernovae (SNe) and gamma-ray bursts (GRBs) are driven by newborn magnetars. Fast-rotating proto-neutron stars have also been of interest as potential sources of gravitational waves (GWs). We show that for a range of rotation periods and magnetic fields, hard X-rays and GeV gamma rays provide us with a promising probe of pulsar-aided SNe. It is observationally known that young pulsar wind nebulae (PWNe) in the Milky Way are very efficient lepton accelerators. We argue that, if embryonic PWNe satisfy similar conditions at early stages of SNe (in ∼1–10 months after themore » explosion), external inverse-Compton emission via upscatterings of SN photons is naturally expected in the GeV range as well as broadband synchrotron emission. To fully take into account the Klein–Nishina effect and two-photon annihilation process that are important at early times, we perform detailed calculations including electromagnetic cascades. Our results suggest that hard X-ray telescopes such as NuSTAR can observe such early PWN emission by follow-up observations in months to years. GeV gamma-rays may also be detected by Fermi for nearby SNe, which serve as counterparts of these GW sources. Detecting the signals will give us an interesting probe of particle acceleration at early times of PWNe, as well as clues to driving mechanisms of luminous SNe and GRBs. Since the Bethe–Heitler cross section is lower than the Thomson cross section, gamma rays would allow us to study subphotospheric dissipation. We encourage searches for high-energy emission from nearby SNe, especially SNe Ibc including super-luminous objects.« less
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