H.E.S.S. and Suzaku observations of the Vela X pulsar wind nebula. (arXiv:1905.07975v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Collaboration_H%2E_E%2E_S%2E_S%2E/0/1/0/all/0/1">H.E.S.S. Collaboration</a>
Pulsar Wind Nebulae (PWNe) represent the most prominent population of
Galactic very-high-energy gamma-ray sources and are thought to be an efficient
source of leptonic cosmic rays. Vela X is a nearby middle-aged PWN, which shows
bright X-ray and TeV gamma-ray emission toward an elongated structure called
the cocoon. Since TeV emission is likely inverse-Compton emission of electrons
while X-ray emission is synchrotron radiation of the same electrons, we aim to
derive the properties of the relativistic particles and of magnetic fields with
minimal modelling. We use data from the Suzaku XIS to derive the spectra from
three compact regions in Vela X covering distances from 0.3 pc to 4 pc from the
pulsar along the cocoon. We obtain gamma-ray spectra of the same regions from
H.E.S.S. observations and fit a radiative model to the multi-wavelength
spectra. The TeV electron spectra and magnetic field strengths are consistent
within the uncertainties for the three regions, with energy densities of the
order $10^{-12}rm,erg,cm^{-3}$. The data indicate the presence of a cutoff
in the electron spectrum at energies of $sim$100 TeV and a magnetic field
strength of $sim$$6,rmmu G$. Constraints on the presence of turbulent
magnetic fields are weak. The pressure of TeV electrons and magnetic fields in
the cocoon is dynamically negligible, requiring the presence of another
dominant pressure component. Sub-TeV electrons cannot account completely for
the missing pressure, that may be provided either by relativistic ions or from
mixing of the ejecta with the pulsar wind. The electron spectra are consistent
with expectations from transport scenarios dominated either by advection via
the reverse shock or by diffusion. Constraints on turbulent magnetic fields and
the shape of the electron cutoff can be improved by spectral measurements in
the energy range $gtrsim 10rm,keV$. (abridged)
Pulsar Wind Nebulae (PWNe) represent the most prominent population of
Galactic very-high-energy gamma-ray sources and are thought to be an efficient
source of leptonic cosmic rays. Vela X is a nearby middle-aged PWN, which shows
bright X-ray and TeV gamma-ray emission toward an elongated structure called
the cocoon. Since TeV emission is likely inverse-Compton emission of electrons
while X-ray emission is synchrotron radiation of the same electrons, we aim to
derive the properties of the relativistic particles and of magnetic fields with
minimal modelling. We use data from the Suzaku XIS to derive the spectra from
three compact regions in Vela X covering distances from 0.3 pc to 4 pc from the
pulsar along the cocoon. We obtain gamma-ray spectra of the same regions from
H.E.S.S. observations and fit a radiative model to the multi-wavelength
spectra. The TeV electron spectra and magnetic field strengths are consistent
within the uncertainties for the three regions, with energy densities of the
order $10^{-12}rm,erg,cm^{-3}$. The data indicate the presence of a cutoff
in the electron spectrum at energies of $sim$100 TeV and a magnetic field
strength of $sim$$6,rmmu G$. Constraints on the presence of turbulent
magnetic fields are weak. The pressure of TeV electrons and magnetic fields in
the cocoon is dynamically negligible, requiring the presence of another
dominant pressure component. Sub-TeV electrons cannot account completely for
the missing pressure, that may be provided either by relativistic ions or from
mixing of the ejecta with the pulsar wind. The electron spectra are consistent
with expectations from transport scenarios dominated either by advection via
the reverse shock or by diffusion. Constraints on turbulent magnetic fields and
the shape of the electron cutoff can be improved by spectral measurements in
the energy range $gtrsim 10rm,keV$. (abridged)
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