Probing the Nature of the Vela X Cocoon

Abstract

Vela X is a pulsar wind nebula (PWN) associated with the active pulsar B0833-45 and contained within the Vela supernova remnant (SNR). A collimated X-ray filament ("cocoon") extends south-southwest from the pulsar to the center of Vela X. VLA observations uncovered radio emission coincident with the eastern edge of the cocoon and H.E.S.S. has detected TeV $\gamma$-ray emission from this region as well. Using XMM-\textit{Newton} archival data, covering the southern portion of this feature, we analyze the X-ray properties of the cocoon. The X-ray data are best fit by an absorbed nonequilibrium plasma model with a powerlaw component. Our analysis of the thermal emission shows enhanced abundances of O, Ne, and Mg within the cocoon, indicating the presence of ejecta-rich material from the propagation of the SNR reverse shock, consistent with Vela X being a disrupted PWN. We investigate the physical processes that excite the electrons in the PWN to emit in the radio, X-ray and $\gamma$-ray bands. The radio and non-thermal X-ray emission can be explained by synchrotron emission. We model the $\gamma$-ray emission by Inverse Compton scattering of electrons off of cosmic microwave background (CMB) photons. We use a 3-component broken power law to model the synchrotron emission, finding an intrinsic break in the electron spectrum at $\sim 5\times 10^6$ keV and a cooling break at $\sim$ 5.5 $\times 10^{10}$ keV. This cooling break along with a magnetic field strength of 5 $\times 10^{-6}$ G indicate that the synchrotron break occurs at $\sim$1 keV.

accepted for publication to ApJL

References in corpus (4)

• First detection of a VHE gamma-ray spectral maximum from a Cosmic source: H.E.S.S. discovery of the Vela X nebula
• Non-thermal emission from relativistic MHD simulations of PWNe: from synchrotron to inverse Compton
• Probing the radio to X-ray connection of the Vela X PWN with Fermi LAT and H.E.S.S
• Physical and chemical inhomogeneities inside the Vela SNR shell. Indications of ejecta shrapnels

Cited by in corpus (8)

• A Dynamical Model for the Evolution of a Pulsar Wind Nebula inside a Non-Radiative Supernova Remnant
• The gas-to-extinction ratio and the gas distribution in the Galaxy
• Pulsar-wind nebulae and magnetar outflows: observations at radio, X-ray, and gamma-ray wavelengths
• Probing the radio to X-ray connection of the Vela X PWN with Fermi LAT and H.E.S.S
• Indications of a Si-rich bilateral jet of ejecta in the Vela SNR observed with XMM-Newton
• A detailed look at the thermal and non-thermal X-ray emission from the Vela supernova remnant with SRG/eROSITA
• X-ray emitting structures in the Vela SNR: ejecta anisotropies and progenitor stellar wind residuals
• The Vela pulsar and its pulsar wind nebula Vela-X using 13 years of Fermi-LAT Observations